Institut de Protection et de Sûreté Nucléaire, Département de Protection de la Santé de l'Homme et de Dosimétrie, Section Autonome de Radiobiologie Appliquée à la Médecine, F-92265 Fontenay-aux-Roses Cedex, France
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ABSTRACT |
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The aim of this
study was to determine whether ionizing radiation modifies muscarinic
regulation of intestinal mucosal function. Rats exposed to total body
8-Gy -irradiation or sham irradiated were studied up to 21 days
after irradiation. Basal and carbachol-stimulated short-circuit current
(Isc) and
transepithelial conductance
(Gt) of
stripped ileum were determined in Ussing chambers. Muscarinic receptor
characteristics using the muscarinic antagonist
[3H]quinuclidinyl
benzilate and three unlabeled antagonists were measured in small
intestinal plasma membranes together with two marker enzyme activities
(sucrase,
Na+-K+-ATPase).
Enzyme activities were decreased 4 days after irradiation (day 4). Basal electrical parameters
were unchanged. Maximal carbachol-induced changes in
Isc and
Gt were increased
at day 4 (maximal
Isc = 195.8 ± 14.7 µA/cm2,
n = 19, vs. 115.4 ± 8.2 µA/cm2,
n = 63, for control rats) and
unchanged at day 7. Dissociation constant was decreased at day 4 (0.73 ± 0.29 nM, n = 10, vs. 2.14 ± 0.39 nM, n = 13, for control rats) but
unchanged at day 7, without change in
binding site number. Thus total body irradiation induces a temporary
stimulation of cholinergic regulation of mucosal intestinal function
that may result in radiation-induced diarrhea.
muscarinic receptor; short-circuit current; rat ileum
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INTRODUCTION |
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INTESTINAL FUNCTIONS are partly controlled by the autonomic nervous system, which is composed of the sympathetic, the parasympathetic, and the enteric nervous systems. The major neurotransmitter of the parasympathetic nervous system is ACh, which is liberated both by extrinsic and intrinsic fibers and can modulate intestinal functions by activation of secretomotor and interneurons (24). In particular, ACh plays a central role in neural regulation of the epithelium because stimulation of active chloride secretion by electrical field stimulation can be partly blocked by the muscarinic antagonist atropine (3, 6). In addition, ACh can act directly on epithelial cells via the stimulation of muscarinic receptors (37). Indeed, the alteration of electrolyte transport in guinea pig ileum and rat colon by exogenously added muscarinic agonists even in the presence of a neural pathways inhibitor (tetrodotoxin) provides evidence for a direct action of muscarinic agonists on epithelial cells (3, 6, 43).
One major consequence of ionizing radiation is the appearance of severe
diarrhea, the etiology of which is to date unknown. Radiation-induced
diarrhea has generally been attributed to an important disruption of
intestinal structure and compromised epithelial integrity. However,
recent studies have reported perturbations of fluid and electrolyte
transport induced by irradiation, in conditions under which no
denudation of the intestinal mucosa and no disruption of the integrity
of the intestinal epithelial barrier were evident (7, 15, 26). In in
vitro studies, modification of both electrical parameters and
electrolyte fluxes have been observed very early after irradiation. In
rabbit ileum, basal short-circuit current
(Isc) and net
serosal-to-mucosal Cl
fluxes were increased while net
Na+ flux was unchanged in less
than 2 days after a 10-Gy irradiation (15). Concerning motility,
several studies have reported that changes in gastrointestinal tract
motility preceded the appearance of histopathological lesions (8). In
particular, in both animal models and patients, small intestinal and
whole gut transit was markedly accelerated within hours after
irradiation (32, 33, 40, 41).
The occurrence of diarrhea may also be ascribed to radiation-induced modifications of the different systems that regulate small intestinal functions (4). The effects of ionizing radiation on some of these regulatory systems have been partly investigated during recent years. In particular, ionizing radiation has been reported to modify the blood and tissue levels of some gastrointestinal regulatory peptides, such as neurotensin and gastrin-releasing peptide (14, 22, 23), that are known to modulate intestinal blood flow, motility, and electrolyte transport. On the other hand, it can be hypothesized that a dysregulation of the autonomic nervous system may participate in the development of diarrhea induced by exposure to ionizing radiation, as has been suggested for diarrhea associated with inflammatory bowel diseases (38). In agreement with this hypothesis, the levels or effects of several neuromodulators, such as substance P and vasoactive intestinal peptide (VIP), have been reported to be modified by ionizing radiation (9, 13). Furthermore, exposure to ionizing radiation also results in altered responses to either neurally evoked electrolyte transport or to exogenously added prostaglandin E2. (10, 16, 26). Finally, Otterson et al. (30) have suggested that the abnormal contractile patterns in canine small intestine observed after irradiation may be related to impaired neural regulation or to abnormal release of gut neuropeptides.
Thus some regulatory systems have been explored, but surprisingly the
effect of ionizing radiation on the classical cholinergic pathway of
regulation of intestinal transport function has not been studied.
Nevertheless, some indirect or direct arguments suggest that modulation
of cholinergic regulation might participate in radiation-induced
dysfunctions and that ionizing radiation may modulate the direct action
of ACh on the enterocyte. An indirect argument was provided by
experiments indicating that ionizing radiation modified levels of
acetylcholinesterase (AChE), the enzyme degrading ACh (5, 11, 30). On
the other hand, a direct argument was provided by the experiments of
Krantis et al. (21), who reported that the contractile responses to
direct smooth muscle stimulation with the muscarinic agonist carbachol was significantly increased in the duodenum and colon but not in the
jejunum of the guinea pig after -irradiation.
Thus the aims of this study were to examine to what extent cholinergic
regulation of intestinal fluid and electrolyte transport in the rat
small intestine is modified by total body -irradiation. First, this
effect was assessed in vitro in the isolated rat ileum by determination
of carbachol-stimulated
Isc and
epithelium conductance (Gt) responses
in Ussing chambers. Second, the determination of mucosal muscarinic
receptor characteristics was performed using a radiolabeled muscarinic
antagonist,
[3H]quinuclidinyl
benzilate (QNB). Finally, different muscarinic antagonists were used
for the determination of receptor subtypes present in small intestinal
mucosa after irradiation.
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MATERIALS AND METHODS |
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Treatment of Animals
Male Wistar rats (Laboratoire CER Janvier) weighing between 250 and 300 g were used in all experiments, allowed food and water ad libitum, and maintained in a constant light and dark environment (12:12-h light-dark cycle).Irradiation protocol. Conscious rats
were placed in Plexiglas tubes and exposed to total body irradiation.
Rats received 8-Gy -irradiation
(60Co source), at a dose rate of 1 Gy/min. Control rats were sham irradiated during the same period.
Experimental procedures were performed from 1 to 21 days
postirradiation. Intestinal samples were removed under anesthesia
(pentobarbital sodium, 60 mg/kg), and then animals were euthanized with
an overdose of anesthetic. All experiments were conducted according to
the French regulations for animal experimentation (Ministry of
Agriculture, Décret no. 87-848, 19 October 1987).
Histology. Histological control of the mucosal structure of samples of jejunum and ileum was performed on another group of rats. Samples were fixed in formaldehyde and embedded in paraffin, and sections were stained with hematoxylin-eosin. Samples were observed for general morphology and organization of the villi, for the mucus state, and for the presence of inflammatory features.
Membrane Preparation
The whole ileum and jejunum were removed and rinsed with 0.9% NaCl, and all procedures were carried out on ice. The mucosal layer was scraped from the underlying muscle layers using a glass slide. For membrane preparation, tissue was homogenized in 10 volumes of sucrose buffer (250 mM sucrose, 2 mM Tris, pH = 7.4) containing the protease inhibitor phenylmethylsulfonyl fluoride (PMSF; 0.1 mM) and centrifuged at 2,500 g for 15 min and then at 20,000 g for 20 min at 4°C. The resulting supernatant was discarded, and the pellet was resuspended in 1 ml of sucrose buffer without PMSF, quickly frozen in liquid nitrogen, and stored atEnzyme Activities
Sucrase activity was determined as described by Mahmood and Alvarado (27), by measurement of D-glucose formation in the presence of glucose oxidase and peroxidase. Na+-K+-ATPase activity was estimated with the use of a ouabain-sensitive, K+-stimulated p-nitrophenyl phosphatase assay (29). Results were expressed per milligram protein, estimated using the dye-binding method of Bradford (2) with bovine serum albumin as standard.Electrolyte Transport Studies
Segments from distal ileum and proximal jejunum were removed and rinsed with 0.9% NaCl. The segments were stripped of external muscle layer, mounted in Ussing chambers, and bathed with warmed, oxygenated (95% O2-5% CO2) Hanks' buffer (pH 7.4) containing (in mM) 127 NaCl, 5 KCl, 0.8 MgSO4, 0.33 Na2HPO4, 0.44 KH2PO4, 1 MgCl2, 4 NaHCO3, 1 CaCl2, 5 D-glucose, 10 Na acetate, and 20 HEPES. Two samples of tissue were tested for each rat. The Isc was monitored permanently, under basal or stimulated conditions. In parallel, Gt was calculated using Ohm's law from values of the current induced when a transepithelial potential difference (PDt) of 2 mV was applied. Basal Isc, Gt, and PDt were determined after 5 min of stabilization. Tissues were then subsequently stimulated by increasing concentrations of carbachol (10Radioligand Binding Studies
About 200 µg of the membrane preparation were incubated with increasing concentrations of the nonselective muscarinic antagonist [3H]QNB (specific activity 49 Ci/mmol), ranging from 50 pM to 2 nM in PBS containing (in mM) 137 NaCl, 2.7 KCl, 0.5 MgCl2, 8 Na2HPO4, 1.5 KH2PO4, 1 CaCl2, pH = 7.2, for 75 min at 30°C. For each concentration of [3H]QNB, the determinations were performed in triplicate and nonspecific binding was determined by the addition of 50 µM atropine in the incubation buffer. Nonspecific binding represented less than 10% of the total binding at concentrations of [3H]QNB near the half-maximal concentration for saturation (dissociation constant; Kd). Bound and free ligand were separated on GF/B Whatman paper filters (preincubated overnight in 0.6% polyethylenimine), using a rapid vacuum filtration system and rinsing three times with 3 ml 10 mM cold Tris solution, pH 7.0. The experiments were performed 1, 3, 4, and 7 days after irradiation on either irradiated or sham-irradiated rats. The radioactivity was counted in a Packard liquid scintillation counter. Analysis of specific binding data was by Scatchard transformation, with the determination of values of Kd and maximal binding capacity (Bmax).Antagonist Displacement Binding Studies
The effect of muscarinic antagonists on [3H]QNB binding were tested only 4 days after irradiation on sham-irradiated or irradiated rats. Membrane preparation was performed, pooling four rats for each experiment, and four experiments were performed for control and irradiated conditions. The labeled antagonist, [3H]QNB (2 nM), and increasing concentrations of three unlabeled muscarinic antagonists were used: atropine (0-5 × 10Chemicals
Methoctramine was obtained from Research Biochemicals International, Natick, MA. Carbamylcholine chloride (carbachol), atropine, pirenzepine, and all other enzyme substrates and salts were from Sigma Chemical, Poole, UK. [3H]QNB (37 TBq/mmol) was from Amersham International, Little Chalfont, UK.Statistical Analysis
Results are expressed as means ± SE. A one-way ANOVA was used to test populations of control rats for enzyme activities and basal electrical parameters. A one-way ANOVA Dunn's test was used for receptor binding characteristics. Mann-Whitney's rank sum test was applied to carbachol-stimulated increases in Isc and Gt. An unpaired t-test was used for inhibitory constant of muscarinic antagonists. Significance was set at P < 0.05. ![]() |
RESULTS |
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For all experiments (determination of Isc, enzyme activities, and receptor characteristics), no significant difference was observed between the control groups of rats tested for the different time after sham irradiation. Consequently, all results for control animals were pooled. Histological examination performed on control and irradiated rats (n = 10) showed no major modification of the mucosal structure.
Determination of Enzyme Activities
Sucrase is an enzyme associated with the apical membrane and is primarily located on the top of the villi. The results presented in Table 1 show that sucrase activity was greatly decreased to 17% of control values 4 days after irradiation (P < 0.05). Nine and 21 days after irradiation, the sucrase activity returned to control values (NS). In parallel, the activity of the basolateral enzyme Na+-K+-ATPase was determined. As shown in Table 1, irradiation modified Na+-K+-ATPase activity with a time-dependent pattern similar to the pattern observed for sucrase. Na+-K+-ATPase activity fell to 40% of control levels 4 days after irradiation (P < 0.05) and returned to control values at day 9 (NS). At day 21, a second decrease in activity of 72% was observed.
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Functionality of Muscarinic Receptors: Ussing Chamber Studies
Basal values of electrical parameters. The mean values of Isc and Gt were determined in basal conditions in ileum samples, and values obtained for control rats and irradiated rats 4 and 7 days after irradiation are reported in Table 2. The basal Isc value (103.1 ± 5.7 µA/cm2, 63 samples for control group) was unchanged by the 8-Gy irradiation whatever the time of experiment. Similar results were obtained for basal Gt (83.0 ± 3.8 mS/cm2 for control group). In parallel, the basal PDt was determined. Irradiation induced no change in PDt whatever the time after irradiation (
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Carbachol-induced increase in
Isc.
Addition of carbachol to the serosal side of the ileal tissue induced a
slow increase in
Isc that reached
a plateau in 4-6 min, depending on the concentration used. The
increase was maintained as long as the agonist was applied. When the
tissue was rinsed, the
Isc returned to
basal levels in 6-10 min. The dose-response curves obtained for
control (63 samples) and irradiated rats at day
4 (23 samples) and day
7 (19 samples) are reported in Fig. 1. The values of maximal
Isc and of
EC50 (estimated from curves representing increases in
Isc as percent of
maximal increase) are reported in Table 2. For all groups the maximal
increase in Isc
was obtained with a dose of 5 × 10
5 M of carbachol. Four
days after irradiation, the amplitude of the maximal carbachol-induced
increase in Isc
was more important than for control conditions (maximal
Isc = 115.4 ± 8.2 µA/cm2 for control vs.
195.8 ± 14.7 µA/cm2
for irradiated rats at day 4). On
the other hand, the estimated EC50
value was unchanged (see Table 2). Seven days after irradiation, the
dose-response curve was again similar to control values, and no change
either in maximal response or in
EC50 value was observed. Similarly, no effect of irradiation on either
Isc or
EC50 values was observed at 1 and
14 days after irradiation (results not shown).
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Carbachol-induced increase in
Gt.
For ileum samples similar dose-response curves were obtained for change
in Gt, expressed
as maximal Gt
or as percent of maximal responses (not shown). Their profile was
exactly similar to the one observed for
Isc. The values
of maximal
Gt
and EC50 reported in Table 2
showed no change in EC50 but an
important change in
Gt 4 days
after irradiation (57.9 ± 3.7 mS/cm2 for control vs. 101.1 ± 8.1 for irradiated rats), with a return to control values 7 days after irradiation.
Characteristics of Muscarinic Receptors
Figure 2A shows an example of a saturation curve obtained for [3H]QNB concentrations ranging from 50 pM to 2 nM, for an irradiated rat 4 days after the 8-Gy irradiation. Analysis of the results by Scatchard analysis of the saturation binding curve fits with a one-binding site model. The values of the receptor characteristics of control rats were 2.14 ± 0.39 nM for Kd and 66.0 ± 11.0 fmol/mg protein for Bmax (n = 13). No change was observed 1 day after irradiation. The Kd was decreased at day 4 after irradiation (Kd = 0.73 ± 0.29 nM, n = 10, P < 0.05), but no significant decrease was observed at day 7 (Kd = 0.78 ± 0.09 nM, n = 4, NS). No significant change in the number of sites (Bmax) was observed whatever the time after irradiation (Bmax = 66.0 ± 11.0 fmol/mg for control rats, n = 13, vs. 42.7 ± 6.6 for irradiated rats at day 4, n = 10).
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Displacement of [3H]QNB Binding by Other Muscarinic Antagonists
Figure 3 shows that [3H]QNB binding is reduced in a dose-dependent manner by increasing concentrations of the three muscarinic antagonists, atropine, methoctramine, and pirenzepine, in sham-irradiated (Fig. 3A) and 8-Gy-irradiated rats (Fig. 3B) 4 days after irradiation. Data points of the displacement curves represent the mean of four experiments for each compound ± SE. IC50 values were estimated for each experiment. No significant change in IC50 value was observed for atropine (1.21 ± 0.39 µM for control vs. 0.47 ± 0.12 µM for irradiated rats, NS) even if there was a tendency to increased sensitivity. On the other hand, IC50 values for both the other antagonists were modified after irradiation: decreased by 71% for pirenzepine (175.0 ± 36.0 µM for control vs. 50.0 ± 12.0 µM for irradiated rats, P < 0.05) but increased by 38% for methoctramine (12.7 ± 1.0 µM for control vs. 17.5 ± 1.4 µM for irradiated rats, P < 0.05) (Table 3).
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DISCUSSION |
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In agreement with other studies on the rat or rabbit ileum (15, 26), no
change was seen in ileal basal electrical parameters whatever the time
after irradiation. MacNaughton et al. (26) reported that in rat ileum
after a 10-Gy -irradiation basal
Isc was not
significantly different 2 h or 1 or 2 days after irradiation, whereas
in ferret jejunum after a 5-Gy
-irradiation basal
Isc was decreased
at 2 h and increased at 2 days after irradiation (25). In their
conditions, Gt
was not modified on the rat ileum at day
1. Furthermore, Gunter-Smith (15) observed in the
rabbit no change in either distal ileal
Isc or
Gt during 4 days
after a 5-Gy irradiation. However, an increase in basal
Isc was observed from 1 day after irradiation with higher doses (7.5 and 10 Gy). In our
conditions, the absence of change in basal parameters suggests no major
disturbance of the integrity of the epithelial barrier. This is in
agreement with our histological analysis using light microscopy, which
revealed no marked structural changes, unlike what was previously
observed in rat ileum at 7 days after a 5-Gy irradiation following
electron microscopic analysis of the structure (31).
In contrast to the absence of change in basal parameters, maximal
carbachol-stimulated responses of both
Isc and
Gt were increased 4 days after irradiation and returned to basal level 7 days after irradiation. No change in EC50 was
observed in our conditions. These results suggest a greater capacity of
ileum to respond to cholinergic stimulation 4 days after irradiation.
This increased capacity of response was also observed in the jejunum,
which suggests that irradiation affects in the same way the different
parts of the small intestine. Our observations are in agreement with
those of Harari et al. (18), who reported an increase in the effect of
stimulation following a single dose of carbachol
(104 M) at 5 days
after a 7-Gy abdominal
-irradiation. It should be noted that the
timing of the effect of irradiation we observed is in agreement with
other transport experiments performed on rat small intestine concerning
D-glucose and water transport
(1). Furthermore, our results are in agreement with experiments
performed by Young and Levin (42), who reported that, in a rat model, progressive starvation for up to 3 days induced no change in either basal Isc or
carbachol-induced increase in
Isc in ileum 1 day after the induction of starvation. However, both basal and
carbachol-stimulated Isc were
increased 3 days after induction of starvation. Food intake is reduced
by irradiation, which suggests that this element is a factor that may
complicate the interpretation of ionizing radiation effects.
In our experimental conditions, the pieces of ileum placed in the
Ussing chamber still contain the submucosal plexus, which may suggest
that when added to the serosal side of the chamber the carbachol may
act via a stimulation of some intrinsic fibers of the enteric nervous
system. MacNaughton et al. (26) have tested the responsiveness of rat
ileum to electrical field stimulation from 2 h to 2 days after a total
body irradiation (10 Gy, ). In these experiments they
observed a decrease in the responsiveness to electrical field
stimulation as soon as 1 day after irradiation. The fact that ionizing
radiation modifies carbachol-induced responses differently compared
with electrical field stimulation-induced responses suggests that
ionizing radiation may affect cholinergic regulation of intestinal
secretory responses not only at the neural level but also at the level
of the enterocyte.
Many factors may contribute to changes in carbachol responsiveness of enterocyte, including alteration in 1) the concentration of drug that reaches the receptor, 2) the efficiency of binding of the drug to the receptor, 3) the number of receptor sites, and 4) the efficiency of coupling of receptors to effector mechanisms. In fact, in our in vitro studies the synthetic agonist used (carbachol) is not degraded by AChE, which suggests that the change in response observed 4 days after irradiation may be associated with either perturbation at the receptor level or at the intracellular transductional level rather than with a change in agonist concentration reaching the receptors.
Modification of receptor characteristics by ionizing radiation has already been reported in the gut for substance P, neurotensin, and VIP (9, 13, 23). Our data show that 4 days after irradiation, characteristics of muscarinic receptors of the small intestine are modified, with a decrease of Kd without a change in the number of binding sites. These observations in addition to the increased intensity of change in Isc induced by carbachol suggest that after irradiation the small intestine is more sensitive to muscarinic regulation. In the control rats the displacement curves indicate an homogeneous population of muscarinic receptor sites. The affinity pattern of the antagonists is consistent with the presence of M2 muscarinic receptors because the IC50 for methoctramine is 10 times smaller than the IC50 for pirenzepine. Our experiments show that after irradiation the sensitivity for the M2 muscarinic antagonist (methoctramine) is decreased (increased IC50), whereas the sensitivity for the M1 muscarinic antagonist (pirenzepine) is increased (decreased IC50) and the sensitivity for the nonselective muscarinic antagonist (atropine) is unchanged. These results show that irradiation modifies the affinity of muscarinic receptors for agonists or antagonists differently depending on the compound used, which may be due to a change in structure or access to the different binding sites.
In fact different processes may take part in modification of muscarinic
receptor characteristics. A first hypothesis concerns a change in
agonist level, which may induce a feedback regulation of receptor
characteristics. It is conceivable that irradiation may modify the
level of ACh. Indeed, irradiation has been reported to be associated
with release of reactive oxygen species (ROS), interleukin-1, and
prostanoids, which have been shown to modulate the level of intestinal
parasympathetic neurotransmitter liberation (12, 28, 34) and thus may
lead to a decreased amount of ACh in irradiated tissue. In this study
we did not measure the level of AChE, the enzyme that degrades ACh, in
intestinal tissue. However, several studies that have addressed this
subject indicate that ionizing radiation modifies levels of AChE,
either decreasing or increasing it depending on the irradiation
procedure (total body or abdominal irradiation) and on the tissue
studied (5, 11, 30). In particular, whole body irradiation
was reported to induce a decrease in ileal and jejunal AChE content (5, 11). These data are consistent with our observation of increased responsiveness to carbachol.
A second hypothesis deals with a possible modification of receptor environment. Ionizing radiation directly or via the production of potent ROS may damage constituents of the cell membrane such as proteins or lipids. Such modifications were reported by Keelan et al. (20) and are in agreement with the attenuation we observed of both apical (sucrase) and basolateral (Na+-K+-ATPase) enzyme activities. Thus ionizing radiation may have a direct effect on the molecular structure of muscarinic receptors. On the other hand, modification of protein and lipid composition can lead to an increase in membrane fluidity and a modification of the receptor environment. In this new environment, the tridimensional structure of the receptor and subsequent binding site conformation may change and so favor or disfavor agonist access to sites. This may lead to modification of binding affinities, as we have observed for muscarinic receptors. In particular, Hulme et al. (19) reported that the affinity of muscarinic receptors was differently modified by solubilization with digitonin depending on the muscarinic type considered. Indeed, the affinity of M2 type receptors was altered, whereas the affinity of M3 type receptors was quite unchanged.
We did not investigate the last hypothesis concerning a possible alteration by ionizing radiation of the signal transduction process associated with muscarinic receptors. Such an alteration has been observed in experiments showing that whole body irradiation of rats with 56Fe may lead to a deficit in striatal muscarinic cholinergic receptor-G protein coupling, reflected by a decrease in GTPase activity (36). Furthermore, ionizing radiation can modulate numerous other elements participating in intracellular signaling, such as intracellular calcium (17, 35), cAMP (13), and inositol trisphosphate receptors (39). Further experiments are required to determine the relative importance of modification of muscarinic transduction system in intestinal tissue.
In conclusion, in this study we observed that total body irradiation induces an upregulation of muscarinic regulation of mucosal fluid and electrolyte transport function in rat small intestine. Our results, together with those of Krantis et al. (21), show that both intestinal motility and electrolyte transport regulated by the cholinergic parasympathetic system can be modified by ionizing radiation, which suggests that this system may be implicated in the development of radiation-induced diarrhea.
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ACKNOWLEDGEMENTS |
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The authors thank C. Maubert and E. Sale for technical assistance and care of animals.
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FOOTNOTES |
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Some of these results were presented at the European Radiation Research Meeting in Oxford, UK, in September 1997.
The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.
Address for reprint requests: F. Lebrun, Institut de Protection et de Sûreté Nucléaire, Département de Protection de la santé de l'Homme et de Dosimétrie, Section Autonome de Radiobiologie Appliquée à la Médecine, BP 6, F-92265 Fontenay-aux-Roses Cedex, France.
Received 14 April 1998; accepted in final form 10 August 1998.
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REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Baer, A. R.,
C. I. Cheeseman,
and
A. B. R. Thomson.
The assessment of recovery of the intestine after acute radiation injury.
Radiat. Res.
109:
319-329,
1987[Medline].
2.
Bradford, M. M.
A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding.
Anal. Biochem.
72:
248-254,
1976[Medline].
3.
Carey, V. H.,
X. Y. Tien,
L. J. Wallace,
and
H. Cooke.
Muscarinic receptor subtypes mediating the mucosal response to neural stimulation of guinea pig ileum.
Am. J. Physiol.
253 (Gastrointest. Liver Physiol. 16):
G323-G329,
1987
4.
Carr, K. E.,
S. P. Hume,
R. Ettarh,
E. A. Carr,
and
J. S. McCullough.
Radiation-induced changes to epithelial and non-epithelial tissue.
In: Radiation and the Gastrointestinal Tract, edited by A. Dubois,
G. L. King,
and D. R. Livengood. Boca Raton, FL: CRC, 1995, p. 113-128.
5.
Conard, R. A.
Some effects of ionizing radiation on the physiology of the gastrointestinal tract: a review.
Radiat. Res.
5:
167-188,
1956.
6.
Diener, M.,
S. F. Knobloch,
R. J. Bridges,
T. Keilmann,
and
W. Rummel.
Cholinergic-mediated secretion in the rat colon: neuronal and epithelial muscarinic responses.
Eur. J. Pharmacol.
168:
219-229,
1989[Medline].
7.
Empey, L. R.,
J. D. Papp,
L. D. Jewell,
and
R. N. Fedorack.
Mucosal protective effects of vitamin E and misoprostol during acute radiation-induced enteritis in rats.
Dig. Dis. Sci.
37:
205-214,
1992[Medline].
8.
Erickson, B. A.,
M. F. Otterson,
J. E. Moulder,
and
S. K. Sarna.
Altered motility causes the early gastrointestinal toxicity of irradiation.
Int. J. Radiat. Oncol. Biol. Phys.
28:
905-912,
1994[Medline].
9.
Esposito, V.,
C. Linard,
C. Maubert,
J. Aigueperse,
and
P. Gourmelon.
Modulation of gut substance P after whole-body irradiation. A new pathological feature.
Dig. Dis. Sci.
41:
2070-2077,
1996[Medline].
10.
François, A.,
J. Aigueperse,
P. Gourmelon,
W. K. MacNaughton,
and
N. M. Griffiths.
Exposure to ionizing radiation modifies neurally-evoked electrolyte transport and some inflammatory responses in rat colon in vitro.
Int. J. Radiat. Biol.
73:
93-101,
1998[Medline].
11.
French, A. B.,
and
P. E. Wall.
Effect of whole body X-irradiation on plasma and intestinal cholinesterase and on drug responses of isolated intestinal loops in the rhesus monkey, rat, and guinea pig.
Am. J. Physiol.
188:
76-80,
1957.
12.
Gaginella, T. S.,
M. B. Grisham,
D. B. Thomas,
R. Walsh,
and
C. Moummi.
Oxidant-evoked release of acetylcholine from enteric neurons of rat colon.
J. Pharmacol. Exp. Ther.
263:
1068-1073,
1992[Abstract].
13.
Griffiths, N. M.,
A. François,
I. Dublineau,
F. Lebrun,
C. Joubert,
J. Aigueperse,
and
P. Gourmelon.
Exposure to either gamma or a mixed neutron/gamma field irradiation modifies vasoactive intestinal peptide receptor characteristics in membranes isolated from pig jejunum.
Int. J. Radiat. Biol.
70:
361-370,
1996[Medline].
14.
Griffiths, N. M.,
W. K. MacNaughton,
C. Linard,
A. François,
V. Esposito,
and
P. Gourmelon.
Ionizing radiation modifies intestinal intercellular communication pathways.
Radioprotection
32:
C1-C25,
1997.
15.
Gunter-Smith, P. J.
Gamma irradiation affects active electrolyte transport by rabbit ileum: basal Na and Cl transport.
Am. J. Physiol.
250 (Gastrointest. Liver Physiol. 13):
G540-G545,
1986[Medline].
16.
Gunter-Smith, P. J.
The effect of radiation on intestinal electrolyte transport.
In: Radiation and the Gastrointestinal Tract, edited by A. Dubois,
G. L. King,
and D. R. Livengood. Boca Raton, FL: CRC, 1995, p. 149-160.
17.
Hallahan, D. E.,
D. Bleakman,
S. Virudachalan,
D. Lee,
D. Grdina,
D. W. Kufe,
and
R. R. Weichselbaum.
The role of intracellular calcium in the cellular response to ionizing radiation.
Radiat. Res.
138:
392-400,
1994[Medline].
18.
Harari, Y.,
D. Kester,
E. Travis,
J. Wallace,
and
G. Castro.
Intestinal anaphylaxis: radiation-induced suppression.
Am. J. Physiol.
267 (Gastrointest. Liver Physiol. 30):
G709-G715,
1994
19.
Hulme, E. C.,
N. J. M. Birdsall,
and
N. J. Buckley.
Muscarinic receptor subtypes.
Annu. Rev. Pharmacol. Toxicol.
30:
633-673,
1990[Medline].
20.
Keelan, M.,
C. Cheeseman,
K. Walker,
and
A. B. R. Thomson.
Effect of external abdominal irradiation on intestinal morphology and brush border membrane enzyme and lipid composition.
Radiat. Res.
105:
84-96,
1986[Medline].
21.
Krantis, A.,
K. Rana,
and
R. K. Harding.
The effects of -radiation on intestinal motor activity and faecal pellet expulsion in the guinea pig.
Dig. Dis. Sci.
41:
2307-2316,
1996[Medline].
22.
Linard, C.,
V. Esposito,
J. Aigueperse,
and
P. Gourmelon.
Influence of irradiation on gastrin releasing peptide (Abstract).
In: Proceedings of the 10th International Congress of Radiation Research, edited by U. Hagen,
H. Jung,
and C. Streffer. Würzburg, Germany: Universitärdruckerei H. Stürtz, 1995, p. 15-18.
23.
Linard, C.,
N. M. Griffiths,
V. Esposito,
J. Aigueperse,
and
P. Gourmelon.
Changes in gut neurotensin and modified colonic motility following whole body irradiation in rat.
Int. J. Radiat. Biol.
71:
581-588,
1997[Medline].
24.
Lundgren, O.,
J. Svanvik,
and
L. Jivegard.
Enteric nervous system. I. Physiology and pathophysiology of the intestinal tract.
Dig. Dis. Sci.
34:
264-283,
1989[Medline].
25.
MacNaughton, W. K.,
K. E. Leach,
L. Prud'homme-Lalonde,
and
R. K. Harding.
Exposure to ionizing radiation increases responsiveness to neural secretory stimuli in the ferret jejunum in vitro.
Int. J. Radiat. Biol.
72:
219-226,
1997[Medline].
26.
MacNaughton, W. K.,
K. E. Leach,
L. Prud'homme-Lalonde,
W. Ho,
and
K. Sharkey.
Ionizing radiation reduces neurally evoked electrolyte transport in rat ileum through a mast cell-dependent mechanism.
Gastroenterology
106:
324-335,
1994[Medline].
27.
Mahmood, A.,
and
F. Alvarado.
Harmaline interaction with sodium-binding sites in intestinal brush border sucrase.
Biochim. Biophys. Acta
483:
367-374,
1977[Medline].
28.
Main, C.,
P. Blennerhassett,
and
S. M. Collins.
Human recombinant interleukin 1 suppresses acetylcholine release from rat myenteric plexus.
Gastroenterology
104:
1648-1654,
1993[Medline].
29.
Murer, H.,
E. Ammann,
J. Biber,
and
U. Hopfer.
The surface membrane of the small intestinal epithelial cell. I. Localization of adenyl cyclase.
Biochim. Biophys. Acta
433:
509-519,
1976[Medline].
30.
Otterson, M. F.,
T. R. Koch,
Z. Zhang,
S. C. Leming,
and
J. E. Moulder.
Fractionated irradiation alters enteric neuroendocrine products.
Dig. Dis. Sci.
40:
1691-1702,
1995[Medline].
31.
Porvaznik, M.
Tight junction disruption and recovery after sublethal -irradiation.
Radiat. Res.
78:
233-250,
1979[Medline].
32.
Summers, R. W.,
A. J. Flatt,
M. Prihoda,
and
F. A. Mitros.
Effect of irradiation on morphology and motility of canine small intestine.
Dig. Dis. Sci.
32:
1402-1409,
1987[Medline].
33.
Summers, R. W.,
T. H. Kent,
and
J. W. Osborne.
Effects of drugs, ileal obstruction, and irradiation on rat gastrointestinal propulsion.
Gastroenterology
59:
731-739,
1970[Medline].
34.
Takeuchi, T.,
M. Okuda,
and
O. Yagasaki.
The differential contribution of endogenous prostaglandins to the release of acetylcholine from the myenteric plexus of the guinea-pig ileum.
Br. J. Pharmacol.
102:
381-385,
1991[Abstract].
35.
Todd, D. G.,
and
R. B. Mikkelsen.
Ionizing radiation induces a transient increase in cytosolic free [Ca2+] in human epithelial tumor cells.
Cancer Res.
54:
5224-5230,
1994[Abstract].
36.
Villalobos-Molina, R.,
J. A. Joseph,
B. M. Rabin,
S. B. Kandasamy,
T. K. Dalton,
and
G. S. Roth.
Iron-56 irradiation diminishes muscarinic but not 1-adrenergic-stimulated low-Km GTPase in rat brain.
Radiat. Res.
140:
382-386,
1994[Medline].
37.
Wahawisan, R.,
L. J. Wallace,
and
T. S. Gaginella.
Muscarinic receptors on rat ileal villus and crypt cells.
J. Pharm. Pharmacol.
38:
150-153,
1986[Medline].
38.
Watson, A.
The cellular basis of diarhoea.
Eur. J. Gastroenterol. Hepatol.
5:
765-773,
1993.
39.
Yan, J.,
K. K. Khanna,
and
M. F. Lavins.
Induction of inositol 1,4,5 triphosphate receptor genes by ionizing radiation.
Int. J. Radiat. Biol.
69:
539-546,
1996[Medline].
40.
Yeoh, E.,
M. Horowitz,
A. Russo,
T. Muecke,
T. Robb,
and
B. Chatterton.
Gastrointestinal function in chronic radiation enteritis: effects of loperamide-N-oxide.
Gut
34:
476-482,
1993[Abstract].
41.
Yeoh, E.,
M. Horowitz,
A. Russo,
T. Muecke,
T. Robb,
A. Maddox,
and
B. Chatterton.
Effect of pelvic irradiation on gastrointestinal function: a prospective longitudinal study.
Am. J. Med.
95:
397-406,
1993[Medline].
42.
Young, A.,
and
R. J. Levin.
Diarrhoea of famine and malnutrition: investigations using a rat model. 2. Ileal hypersecretion induced by starvation.
Gut
31:
162-169,
1990[Abstract].
43.
Zimmerman, T. W.,
J. W. Dobbins,
and
H. J. Binder.
Mechanism of cholinergic regulation of electrolyte transport in rat colon in vitro.
Am. J. Physiol.
242 (Gastrointest. Liver Physiol. 5):
G116-G123,
1982