1 Department of Physiology, The University of Michigan, Ann Arbor, Michigan 48109-0622; and 2 Department of Clinical Biochemistry Rigshospitalet, DK 2100 Copenhagen, Denmark
![]() |
ABSTRACT |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
A CCK-deficient mouse mutant generated by gene targeting in embryonic stem cells was analyzed to determine the importance of CCK for growth and function of the exocrine pancreas and for pancreatic adaptation to dietary changes. RIAs confirmed the absence of CCK in mutant mice and demonstrated that tissue concentrations of the related peptide gastrin were normal. CCK-deficient mice are viable and fertile and exhibit normal body weight. Pancreas weight and cellular morphology appeared normal, although pancreatic amylase content was elevated in CCK-deficient mice. We found that a high-protein diet increased pancreatic weight, protein, DNA, and chymotrypsinogen content similarly in CCK-deficient and wild-type mice. This result demonstrates that CCK is not required for protein-induced pancreatic hypertrophy and increased proteolytic enzyme content. This is a novel finding, since CCK has been considered the primary mediator of dietary protein-induced changes in the pancreas. Altered somatostatin concentrations in brain and duodenum of CCK-deficient mice suggest that other regulatory pathways are modified to compensate for the CCK deficiency.
gastrointestinal hormones; knockout mice; acinar cells; digestive enzymes; pancreatic hypertrophy
![]() |
INTRODUCTION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
THE TROPHIC EFFECTS of CCK on the exocrine pancreas have been extensively studied. Exogenous CCK stimulates growth of the exocrine pancreas in adult (41, 42, 51) and neonatal rodents (46, 48, 51). Prolonged administration of high concentrations of CCK induces the formation of hyperplastic and neoplastic nodules (16). The feeding of trypsin inhibitors (29, 30, 47) and pancreatic juice diversion (10, 26) each stimulates the release of endogenous CCK and induces pancreatic growth. Moreover, prolonged treatment with CCK-A receptor antagonists decreases pancreatic weight, protein content, and DNA content in mice and rats under some experimental conditions (29, 31, 44, 47). These studies suggest that CCK plays an important role in pancreatic growth and maintenance. However, there are also studies that fail to demonstrate growth inhibition following the administration of CCK antagonists in rodents (12, 30, 47, 51).
Increases in dietary protein also stimulate pancreatic hypertrophy and lead to increases in the expression of proteolytic enzymes (12, 13). These changes in the pancreas are believed to result from elevated CCK concentrations in plasma, since dietary protein stimulates the release of endogenous CCK (14, 23). Accordingly, Green and colleagues (12, 27) have demonstrated that CCK antagonists inhibit the induction and maintenance of pancreatic hypertrophy produced by dietary protein.
It is clear from these studies that CCK stimulates pancreatic growth. However, whether CCK is required for normal growth and development of the pancreas is less clear, since the effectiveness of CCK receptor antagonists in vivo appears variable. To address the physiological requirement for CCK in whole animals, we have established a CCK-deficient mouse model by gene targeting in mouse embryonic stem (ES) cells. We have examined the overall histology of the gastrointestinal tract, as well as the ability of the pancreas to adapt to changes in dietary protein in this model. Because CCK may function as a satiety factor, we also tracked normal body weight gain in the CCK-deficient mice.
![]() |
MATERIALS AND METHODS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Generation of CCK-deficient mice.
CCK-deficient mice were generated by gene targeting in the R1 ES cell
line (28). The targeting vector contained 7.5 kb of mouse CCK genomic
DNA, including 6.5 kb in the 5' arm and 1.0 kb in the 3'
arm (BssH
II-Sal I) (Fig.
1). The bacterial
lacZ reporter gene from plasmid pCH110
(Pharmacia) and a neomycin phosphotransferase selection cassette
controlled by the phosphoglycerate kinase-1 promoter from plasmid pPNT
(45) were inserted into exon 2 at the site of a 168-bp deletion of CCK
sequence. The deletion completely removed the
NH2 terminus of CCK, including the
signal sequence. The lacZ reporter was
positioned at the CCK translational start site. R1 cell culture and
gene targeting were performed as described previously (9). Correctly
targeted cell lines were identified after screening by PCR and
confirmed by long-range PCR and Southern blot analysis as described in
Lay et al. (22). Six targeted cell lines were microinjected into
C57BL/6J blastocysts, with three ES clones yielding chimeric mice that
transmitted the targeted mutation through the germ line. Germ line
chimeric males were mated to 129/SvJ females, and heterozygous progeny
were intercrossed to generate homozygous CCK-deficient and wild-type
mice. Mice used in this study were generated by homozygous matings.
Mouse genotypes were determined by PCR analysis of tail DNA
preparations with primers specific for the wild-type (CS1 and CS2) and
mutant (CS1 and LZ) alleles as follows: CS1,
5'-CTGGTTAGAAGAGAGATGAGCTACAAAGGC; CS2,
5'-TAGGACTGCCATCACCACGCACAGACATAC; LZ,
5'-TGTAGATGGGCGCATCGTAACCGTGCATCT.
|
|
Histology. Gastrointestinal tissues were dissected from adult mice, rinsed in ice-cold PBS, and fixed in 4% paraformaldehyde in PBS (4-6 h). The fixed tissues were embedded in paraffin, sectioned (3 µm), and stained with hematoxylin and eosin.
Gastrointestinal peptide quantitation. Tissues were rapidly dissected from mice that were fasted overnight but had free access to water. Gastrointestinal tissues were gently rinsed in ice-cold PBS before freezing in liquid nitrogen. Tissue extracts for RIA were prepared as previously described (35). Carboxyamidated and O-sulfated CCK (bioactive CCK) was measured using antibody 92128 (33). Other peptides measured by RIA utilized the following antibodies: amidated gastrin, antibody 2604 (36); somatostatin, antibody R37 (34); COOH-terminal chromogranin A, antibody 95037 (Rehfeld, unpublished observations).
Pancreatic adaptation to specialized diets. Six- to seven-week-old male mice were divided into three groups and fed either high-protein, high-carbohydrate, or high-fat diets for 15 days (see Table 1 for diet formulations). Both wild-type and CCK-deficient mice were fed ad libitum for the duration of the study, and food intake was monitored. After 2 wk, mice were weighed and killed. The pancreas was dissected, weighed, and frozen in liquid nitrogen.
For measurement of protein, DNA, and enzyme content, each pancreas was homogenized (Polytron) for 1 min in 4 ml of homogenate buffer (5 mM MgCl2-0.1% Triton X-100) and sonicated for 30 s. Protein measurements were made using the Bio-Rad protein assay kit (Bradford method) using BSA as standard. Aliquots for DNA analysis contained 2.5 M NaCl, and DNA was measured fluorometrically using the TKO 100 minifluorometer (Hoefer Scientific) with Hoechst 33258 dye and calf thymus DNA as standard.Pancreatic enzyme assays. Amylase activity was assayed in pancreatic homogenates using a method modified from previous studies (3, 19). Reactions containing 50 µl of diluted pancreatic homogenate and 50 µl of 1% starch solution in amylase buffer (20 mM NaPO4, pH 6.9, 6 mM NaCl, 1 mg/ml BSA) were incubated at 30°C for 5 min. At the end of the incubation, 100 µl of stop solution were added (1:1 mixture of 2% dinitrosalicylate in 0.4 M NaOH and 60% sodium potassium tartrate in 0.4 M NaOH), and the samples were placed in a boiling water bath for 5 min. Reactions were cooled to room temperature for 10 min, 1 ml H2O was added, and absorbance was read at 540 nm. All samples and standards were assayed in duplicate. Samples for the standard curve contained 0-0.3 µmol maltose in amylase buffer. One unit of amylase activity liberates 1 µmol maltose/min at 30°C (3, 19).
Chymotrypsinogen content was measured in duplicate in pancreatic homogenates using a protocol adapted from Erlanger et al. (8). Diluted pancreatic homogenate (100 µl) was activated with 10 µl of trypsin (0.1 mg/ml amylase buffer) and placed on ice for 1 h. One milliliter of substrate buffer (2% glutaryl-L-phenylalanine p-nitroanilide in 50 mM Tris · HCl, 20 mM CaCl2 · 2H2O, 3.0 M NaCl, pH 7.6) was added to the trypsin-activated samples and incubated at 37°C for 30 min. Reactions were stopped with 1 ml of 20% acetic acid, and the absorbance was read at 410 nm. Chymotrypsinogen content in the pancreatic homogenates was adjusted to chymotrypsin weight by comparison to a standard curve containing 0-100 µg chymotrypsin (Sigma type 1-S) in homogenate buffer.RNase protection analysis. Total RNA was extracted from frozen tissue by a guanidine thiocyanate homogenization-CsCl centrifugation method (38). The CCK-A receptor riboprobe was generated by in vitro transcription of a 310-bp EcoR I-Pst I fragment from the 3' untranslated region of the mouse gene (21) using the riboprobe system (Promega), [32P]UTP, and T3 polymerase. RNase protection was performed with the RPA II ribonuclease protection assay kit (Ambion) as previously described (21). Pancreatic RNA (50 µg) was hybridized overnight at 45°C with 5 × 104 counts/min (cpm) of spin-column-purified riboprobe. After hybridization, the samples were RNase digested for 1 h at 37°C. To test probe specificity, digests were ethanol precipitated in the presence of 10 µg of yeast tRNA as a carrier and resolved by electrophoresis on 8% denaturing polyacrylamide gels (not shown). To quantitate transcript abundance, RNase-digested samples were precipitated on ice for 1 h in 10% TCA and 50 µg salmon sperm DNA. Precipitates were collected on Whatman GF/C filters and washed five times with 10% TCA and five times with 95% ethanol. Filters were air dried and immersed in scintillation fluid for counting. Fifty micrograms of yeast tRNA and mouse liver RNA were used as negative controls. All samples were assayed in triplicate.
Intracellular Ca2+ signaling. Pancreatic acinar cells were isolated from two to three free-fed mice by collagenase digestion as previously described (5). Acini were suspended in HR incubation buffer (10 mM HEPES, pH 7.4, 127 mM NaCl, 4.7 mM KCl, 0.6 mM MgCl2, 1.3 mM CaCl2, 0.6 mM Na2HPO4, 2.0 mg/ml glucose, MEM amino acid supplement, 2 mM L-glutamine, 1% BSA, and 0.01% soybean trypsin inhibitor), preincubated for 1 h with 1 µM fura 2-AM, and then washed with HR buffer. Fura 2-loaded acinar cell clusters were transferred to a closed chamber, mounted on the stage of a Zeiss Axiovert-inverted microscope, and continuously perfused with HR buffer alone or HR buffer containing secretin (10 µM), CCK (10 pM), or carbachol (10 µM). Intracellular Ca2+ measurement by fura 2 utilized an Attoflour dual-excitation wavelength digital imaging system (Rockville, MD) (15, 24, 49).
Statistics. Statistical analysis was carried out using SYSTAT software. An unpaired t-test was used for two-group comparisons, and ANOVA followed by Tukey's post hoc test was used for multiple-group comparisons. All values are expressed as means ± SE.
![]() |
RESULTS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Generation of CCK-deficient mice.
A mouse strain with a CCK gene mutation was generated by gene targeting
in mouse ES cells. The targeting event disrupted the protein coding
region by insertion of the bacterial
lacZ reporter gene at the
translational start site (Fig. 1). Heterozygous matings resulted in the
expected Mendelian ratios of homozygous CCK-deficient mutants,
heterozygotes, and wild-type mice (1:2:1). The homozygous CCK-deficient
mice produced from these matings were viable and fertile and developed
without gross abnormalities. Measurement of body weight in males and
females showed that mutant mice grow at a normal rate compared with
wild-type controls (Fig. 1B). RIA of
tissue extracts confirmed the absence of bioactive CCK in the brain and
duodenum (Table 2), demonstrating that the
targeted gene rearrangement produced a null mutant mouse.
|
Pancreatic enzyme content.
Although overall pancreatic growth and morphology appeared normal in
CCK-deficient mice, digestive enzyme content differed. Analysis of
pancreatic enzymes in CCK-deficient mice fed the basal diet revealed
60% more pancreatic amylase compared with wild-type mice (Table
3). Chymotrypsinogen content was
unaffected, suggesting that the high pancreatic amylase content in
CCK-deficient mice is most likely due to elevated amylase synthesis and
not a general inhibition of pancreatic enzyme secretion.
|
Pancreatic adaptation to dietary protein.
CCK-deficient and wild-type mice were fed diets high in protein,
carbohydrate, or fat for 2 wk to determine if CCK is required for
pancreatic adaptation to diet. Mice fed the high-protein diet maintained normal body weight compared with mice fed the standard chow
(basal) (Fig.
2A). CCK
was previously thought to be necessary for dietary protein-induced
pancreatic growth; however, CCK-deficient mice still exhibited
increased pancreatic weight when fed the high-protein diet compared
with mice fed the other three diets (basal, high carbohydrate, and high
fat) (Fig. 2B). The basal diet
contains a moderate amount of protein. Accordingly, the pancreatic weights of mice maintained on the basal diet were intermediate between
the high-protein and low-protein (the high-carbohydrate and high-fat)
diets. There were no differences in the pancreatic weights of mutant
and wild-type mice fed similar diets.
|
|
|
CCK receptor expression.
Because the CCK-A-type receptor mediates CCK regulation of the exocrine
pancreas in the mouse, we measured CCK-A receptor mRNA levels to
determine if hormone deficiency alters receptor gene expression. CCK-A
receptor transcripts were quantitated by RNase protection assay using a
riboprobe derived from the 3' untranslated region of the mouse
CCK-A receptor gene. The concentration of CCK-A receptor mRNA was
normal in CCK-deficient mice compared with wild-type controls (Fig.
5), suggesting that agonist binding does
not regulate receptor gene expression. In addition, pancreatic acinar
cells from CCK-deficient mice responded to physiological doses of CCK
(10 pM) to produce normal oscillatory changes in intracellular
Ca2+, even though the acinar cells
were naive to the CCK hormone (Fig. 6).
Secretin did not alter intracellular
Ca2+ concentrations in acinar
cells from CCK-deficient mice, a result consistent with wild-type mice,
since the secretin receptor is normally coupled to the cAMP signaling
pathway.
|
|
Other gastrointestinal peptides. We examined other gastrointestinal peptides to determine if their concentrations changed as a consequence of the CCK deficit. Gastrin levels in the brain, stomach, and duodenum from CCK-deficient mice were normal compared with wild-type controls, supporting the conclusion that gastrin is not upregulated to compensate for the loss of CCK (Table 2). However, somatostatin concentrations were significantly different in the CCK mutant. In the duodenum, CCK-deficient mice have 25% less somatostatin. In contrast, somatostatin concentrations increased 18% in the brain of CCK-deficient mice (Table 2). In the stomach, somatostatin concentrations were not significantly different in CCK-deficient mice compared with wild-type controls. Chromogranin A, a marker of neuroendocrine cells, remained unchanged, indicating that CCK deficiency does not grossly alter neuroendocrine cell numbers in the brain or the duodenum.
![]() |
DISCUSSION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
A CCK-deficient mouse model was successfully generated by gene targeting in ES cells. The RIA data presented here confirm that this new mutant mouse strain does not produce CCK. CCK-deficient mice are viable and grow at a normal rate. Aging mice (1 yr and older) continued to thrive, with no obviously abnormal pathologies. The body weight, rate of weight gain (Fig. 1B), and total daily food intake (data not shown) of CCK-deficient mice do not differ from wild-type mice, suggesting that CCK is not essential for maintaining normal energy balance (intake vs. expenditure).
Analysis of pancreatic enzyme content in CCK-deficient mice fed the basal diet revealed an increase in amylase enzyme activity (Table 3). Because chymotrypsinogen content remained unaltered in the mutant, we concluded that the increase in amylase is not due to a general reduction in enzyme secretion but a specific increase in amylase synthesis. Previous studies have demonstrated an inhibitory effect of CCK on amylase synthesis (43). This effect has not always been apparent in mice (29, 31). Yet our results indicate that CCK does exert some inhibition on amylase synthesis in the mouse pancreas, resulting in elevated amylase content when CCK is chronically absent. In contrast to CCK, insulin acts as a potent stimulator of pancreatic amylase content in rats and mice (6, 20). Thus we propose that lack of CCK results in an imbalance of inhibitory and stimulatory signals, resulting in elevated amylase synthesis.
Previous studies have produced conflicting reports regarding the role of CCK in normal development and growth of the pancreas; however, the CCK-deficient mouse clearly demonstrates that CCK is not a required growth factor for the pancreas. Moreover, our analysis showed that CCK is not necessary for pancreatic adaptation to a high-protein diet. This result was unexpected considering the wealth of literature demonstrating a primary role for CCK in protein-induced pancreatic hypertrophy. Both short- and long-term studies in the mouse demonstrated that the CCK-A receptor antagonist CR-1409 blocks pancreatic hypertrophy in response to feeding the trypsin inhibitor camostat (29, 30). Moreover, short-term (10 days) administration of CCK-A receptor antagonists alone produced pancreatic atrophy (29, 31). However, long-term CR-1409 administration did not induce atrophy, suggesting that over time other pathways may compensate for the loss of CCK (30). Our analysis of the CCK-deficient mouse supports the conclusion that compensatory mechanisms may arise when CCK function is blocked long term. The CCK-deficient mouse model will be useful for identifying alternative regulatory peptides or neural mechanisms that can regulate the pancreas.
Although gastrin is closely related to CCK and they both recognize the CCK-B receptor, it is unlikely that gastrin compensates for CCK deficiency. Our data show no change in gastrin tissue concentrations or sites of expression. Likewise, RNase protection analysis indicated that CCK-B receptor expression does not replace CCK-A receptor in the pancreas of CCK-deficient mice (data not shown). Similarly, our laboratory has generated a double mouse mutant by crossing the CCK-deficient mouse described here to the gastrin-deficient mouse described by Friis-Hansen et al. (9). The double mutant exhibits no change in pancreatic morphology (data not shown), supporting the hypothesis that gastrin is not compensating for the lack of CCK.
Interestingly, somatostatin concentrations in CCK-deficient mice were significantly lower in the duodenum, whereas brain concentrations were increased. Previous studies have demonstrated that CCK stimulates somatostatin secretion and synthesis (7, 23, 50). In addition, somatostatin also decreases CCK release from the intestine (17, 37, 40). Thus CCK and somatostatin may participate in a feedback loop affecting pancreatic function. In the brain, somatostatin may act as an inhibitor of feeding. Because CCK has been shown to inhibit short-term food intake, it is intriguing to propose that somatostatin may be upregulated in the brain to somehow compensate for the loss of CCK. Some of the obesity mouse mutants show similar patterns of decreased somatostatin expression in the gastrointestinal tract and increases in the central nervous system (32). Because somatostatin expression occurs in many tissues and affects a variety of systems, it may play a modulatory role and help in compensating for physiological imbalance, such as in the case of the CCK-deficient mouse.
In addition to providing a useful model to study alternative regulatory pathways compensating for the lack of CCK stimulation of the pancreas, the CCK-deficient mouse generated in this study will be useful for investigating CCK functions in other gastrointestinal processes, such as gallbladder contraction, gastric emptying, and intestinal motility. In addition, analysis of feeding behavior in this mutant can test the importance of CCK in regulating short-term satiety responses and long-term food intake. Both endogenous and exogenous CCK can inhibit short-term food intake, and recent studies suggest that CCK may contribute to leptin action (1, 2, 25). Further analysis of CCK-deficient mice will help elucidate CCK's contribution to the complex mechanisms regulating food intake and body weight.
![]() |
ACKNOWLEDGEMENTS |
---|
We thank John Williams and Craig Logsdon for helpful discussions, David Giovannucci and Bradley Segura for Ca2+ signaling measurements, Steve Ernst and Joel Greenson for histological analyses, Jeffrey Friedman for the mouse CCK clone, Andras Nagy, Reka Nagy, and Wanda Abramow-Newerly for R1 ES cells, Richard Mulligan for the pPNT vector, and Sally Camper and the University of Michigan Transgenic Animal Model Core for assistance with gene targeting.
![]() |
FOOTNOTES |
---|
This work was supported by the University of Michigan Gastrointestinal Center, Cancer Center and Organogenesis Center, and National Institute of Diabetes and Digestive and Kidney Diseases Grant DK-48815 (to L. C. Samuelson). K. A. Lacourse was supported by the Cellular and Molecular Aspects of Systems and Integrative Biology Training Grant (5T32GM08322) and by a University of Michigan Rackham predoctoral fellowship.
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 and other correspondence: L. C. Samuelson, Dept. of Physiology, 7761 Med. Sci. II, The Univ. of Michigan, Ann Arbor, MI 48109-0622 (E-mail: lcsam{at}umich.edu).
Received 10 November 1998; accepted in final form 17 February 1999.
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Bado, A.,
S. Levasseur,
S. Attoub,
A. Kermorgant,
J.-P. Laigneau,
N.-N. Bortoluzzi,
L. Moizo,
T. Lehy,
M. Guerre-Millo,
Y. Le Marchand-Brustel,
and
M. J. M. Lewin.
The stomach is a source of leptin.
Nature
394:
790-793,
1998[Medline].
2.
Barrachina, M. D.,
V. Martinez,
L. Wang,
J. Y. Wei,
and
Y. Taché.
Synergistic interaction between leptin and cholecystokinin to reduce short-term food intake in mice.
Proc. Natl. Acad. Sci. USA
94:
10455-10460,
1997
3.
Baum, B. J.,
I. S. Ambudkar,
J. Helman,
V. J. Horn,
J. E. Melvin,
L. M. Mertz,
and
R. J. Turner.
Dispersed salivary gland acinar cell preparations for use in studies of neuroreceptor-coupled secretory events.
Methods Enzymol.
192:
26-37,
1990[Medline].
4.
Brannon, P. M.
Adaptation of the exocrine pancreas to diet.
Annu. Rev. Nutr.
10:
85-105,
1990[Medline].
5.
Burnham, D. B.,
and
J. A. Williams.
Effects of carbachol, cholecystokinin, and insulin on protein phosphorylation in isolated pancreatic acini.
J. Biol. Chem.
257:
10523-10528,
1982
6.
Danielsson, Å.
Effects of nutritional state and of administration of glucose, glibenclamide or diazoxide on the storage of amylase in mouse pancreas.
Digestion
10:
150-161,
1974[Medline].
7.
Dickinson, C. J.,
J. Del Valle,
A. Todisco,
I. Gantz,
L. Tong,
S. Finniss,
and
T. Yamada.
Canine prosomatostatin: isolation of a cDNA, regulation of gene expression, and characterization of post-translational processing intermediates.
Regul. Pept.
67:
145-152,
1996[Medline].
8.
Erlanger, B. F.,
F. Edel,
and
A. G. Cooper.
The action of chymotrypsin on two new chromogenic substrates.
Arch. Biochem. Biophys.
115:
206-210,
1966[Medline].
9.
Friis-Hansen, L.,
F. Sundler,
Y. Li,
P. J. Gillespie,
T. L. Saunders,
J. K. Greenson,
C. Owyang,
J. F. Rehfeld,
and
L. C. Samuelson.
Impaired gastric acid secretion in gastrin-deficient mice.
Am. J. Physiol.
274 (Gastrointest. Liver Physiol. 37):
G561-G568,
1998
10.
Gasslander, T.,
J. Axelson,
R. Håkanson,
I. Ihse,
I. Lilja,
and
J. F. Rehfeld.
Cholecystokinin is responsible for growth of the pancreas after pancreaticobiliary diversion in rats.
Scand. J. Gastroenterol.
25:
1060-1065,
1990[Medline].
11.
Giorgi, D.,
W. Renaud,
J. P. Bernard,
and
J. C. Dagorn.
Regulation of proteolytic enzyme activities and mRNA concentrations in rat pancreas by food content.
Biochem. Biophys. Res. Commun.
127:
937-942,
1985[Medline].
12.
Green, G. M.,
G. Jurkowska,
F. L. Berube,
N. Rivard,
D. Guan,
and
J. Morisset.
Role of cholecystokinin in induction and maintenance of dietary protein-stimulated pancreatic growth.
Am. J. Physiol.
262 (Gastrointest. Liver Physiol. 25):
G740-G746,
1992
13.
Green, G. M.,
V. H. Levan,
and
R. A. Liddle.
Plasma cholecystokinin and pancreatic growth during adaptation to dietary protein.
Am. J. Physiol.
251 (Gastrointest. Liver Physiol. 14):
G70-G74,
1986[Medline].
14.
Green, G. M.,
S. Taguchi,
J. Friestman,
W. Y. Chey,
and
R. A. Liddle.
Plasma secretin, CCK, and pancreatic secretion in response to dietary fat in the rat.
Am. J. Physiol.
256 (Gastrointest. Liver Physiol. 19):
G1016-G1021,
1989
15.
Grynkiewicz, G.,
M. Poenie,
and
R. Y. Tsien.
A new generation of Ca2+ indicators with greatly improved fluorescence properties.
J. Biol. Chem.
260:
3440-3450,
1985[Abstract].
16.
Gumbmann, M. R.,
G. M. Dugan,
W. L. Spangler,
E. C. Baker,
and
J. J. Rackis.
Pancreatic response in rats and mice to trypsin inhibitors from soy and potato after short- and long-term dietary exposure.
J. Nutr.
119:
1598-1609,
1989[Medline].
17.
Heintges, T.,
R. Lüthen,
and
C. Niederau.
Inhibition of exocrine pancreatic secretion by somatostatin and its analogues.
Digestion
55, Suppl. 1:
1-9,
1994[Medline].
18.
Herzig, K. H.,
D. S. Louie,
and
C. Owyang.
Somatostatin inhibits CCK release by inhibiting secretion and action of CCK-releasing peptide.
Am. J. Physiol.
266 (Gastrointest. Liver Physiol. 29):
G1156-G1161,
1994
19.
Hjorth, J. P.,
M. Meisler,
and
J. T. Nielsen.
Genetic variation in amount of salivary amylase in the bank vole, Clethrionomys glareola.
Genetics
92:
915-930,
1979
20.
Korc, M.,
D. Owerbach,
C. Quinto,
and
W. J. Rutter.
Pancreatic islet-acinar cell interaction: amylase messenger RNA levels are determined by insulin.
Science
213:
351-353,
1981[Medline].
21.
Lacourse, K. A.,
J. M. Lay,
L. J. Swanberg,
C. Jenkins,
and
L. C. Samuelson.
Molecular structure of the mouse CCK-A receptor gene.
Biochem. Biophys. Res. Commun.
236:
630-635,
1997[Medline].
22.
Lay, J. M.,
L. Friis-Hansen,
P. J. Gillespie,
and
L. C. Samuelson.
Rapid confirmation of gene targeting in embryonic stem cells using two long-range PCR techniques.
Transgenic Res.
7:
135-140,
1998[Medline].
23.
Lewis, L. D.,
and
J. A. Williams.
Regulation of cholecystokinin secretion by food, hormones, and neural pathways in the rat.
Am. J. Physiol.
258 (Gastrointest. Liver Physiol. 21):
G512-G518,
1990
24.
Matozaki, T.,
B. Göke,
Y. Tsunoda,
M. Rodriguez,
J. Martinez,
and
J. A. Williams.
Two functionally distinct cholecystokinin receptors show different modes of action on Ca2+ mobilization and phospholipid hydrolysis in isolated rat pancreatic acini.
J. Biol. Chem.
265:
6247-6254,
1990
25.
Matson, C. A.,
M. F. Wiater,
J. L. Kujiper,
and
D. S. Weigle.
Synergy between leptin and cholecystokinin (CCK) to control daily caloric intake.
Peptides
18:
1275-1278,
1997[Medline].
26.
Miazza, B. M.,
Y. Turberg,
P. Guillaume,
W. Hahne,
J. A. Chayvialle,
and
E. Loizeau.
Mechanism of pancreatic growth induced by pancreatico-biliary diversion in the rat.
Scand. J. Gastroenterol.
112:
75-83,
1985.
27.
Morisset, J.,
D. Guan,
G. Jurkowska,
N. Rivard,
and
G. M. Green.
Endogenous cholecystokinin, the major factor responsible for dietary protein-induced pancreatic growth.
Pancreas
7:
522-529,
1992[Medline].
28.
Nagy, A.,
J. Rossant,
R. Nagy,
W. Abramow-Newerly,
and
J. C. Roder.
Derivation of completely cell culture-derived mice from early-passage embryonic stem cells.
Proc. Natl. Acad. Sci. USA
90:
8424-8428,
1993
29.
Niederau, C.,
R. A. Liddle,
J. A. Williams,
and
J. H. Grendell.
Pancreatic Growth: Interaction of exogenous cholecystokinin, a protease inhibitor, and a cholecystokinin receptor antagonist in mice.
Gut
28:
63-69,
1987[Medline].
30.
Niederau, C.,
R. Lüthen,
M. Niederau,
G. Strohmeyer,
L. D. Ferrell,
and
J. H. Grendell.
Effects of long-term CCK stimulation and CCK blockade on pancreatic and intestinal growth, morphology, and function.
Digestion
46:
217-225,
1990[Medline].
31.
Niederau, C.,
M. Niederau,
H. Klonowski,
R. Lüthen,
and
L. D. Ferrell.
Effect of hypergastrinemia and blockade of gastrin-receptors on pancreatic growth in the mouse.
Hepatogastroenterology
42:
423-431,
1995[Medline].
32.
Patel, Y. C.,
D. P. Cameron,
Y. Stefan,
F. Malaisse-Lagae,
and
L. Orci.
Somatostatin: widespread abnormality in tissues of spontaneously diabetic mice.
Science
198:
930-931,
1977[Medline].
33.
Rehfeld, J. F.
Accurate measurement of cholecystokinin in plasma.
Clin. Chem.
44:
991-1001,
1998
34.
Rehfeld, J. F.
Sequence specific radioimmunoassays for cholecystokinin, gastrin, and somatostatin.
Biomed. Res. (Tokyo)
1:
73-78,
1980.
35.
Rehfeld, J. F.,
L. Bardram,
and
L. Hilsted.
Ontogeny of procholecystokinin maturation in rat duodenum, jejunum, and ileum.
Gastroenterology
103:
424-430,
1992[Medline].
36.
Rehfeld, J. F.,
F. Stadil,
and
B. Rubin.
Production and evaluation of antibodies for the radioimmunoassay of gastrin.
Scand. J. Clin. Lab. Invest.
30:
221-232,
1972[Medline].
37.
Rivard, N.,
D. Guan,
C. M. Turkelson,
D. Petitclerc,
T. E. Solomon,
and
J. Morisset.
Negative control by sandostatin on pancreatic and duodenal growth: a possible implication of insulin-like growth factor I.
Regul. Pept.
34:
13-23,
1991[Medline].
38.
Samuelson, L. C.,
P. R. Keller,
G. J. Darlington,
and
M. H. Meisler.
Glucocorticoid and developmental regulation of amylase mRNAs in mouse liver cells.
Mol. Cell. Biol.
8:
3857-3863,
1988[Medline].
39.
Schmid, R. M.,
and
M. H. Meisler.
Dietary regulation of pancreatic amylase in transgenic mice mediated by a 126-base pair DNA fragment.
Am. J. Physiol.
262 (Gastrointest. Liver Physiol. 25):
G971-G976,
1992
40.
Shiratori, K.,
S. Watanabe,
and
T. Takeuchi.
Somatostatin analog, SMS 201-995, inhibits pancreatic exocrine secretion and release of secretin and cholecystokinin in rats.
Pancreas
6:
23-30,
1991[Medline].
41.
Solomon, T. E.,
H. Petersen,
J. Elashoff,
and
M. I. Grossman.
Interaction of caerulein and secretin on pancreatic size and composition in rat.
Am. J. Physiol.
235 (Endocrinol. Metab. Gastrointest. Physiol. 4):
E714-E719,
1978
42.
Solomon, T. E.,
M. Vanier,
and
J. Morisset.
Cell site and time course of DNA synthesis in pancreas after caerulein and secretin.
Am. J. Physiol.
245 (Gastrointest. Liver Physiol. 8):
G99-G105,
1983
43.
Steinhilber, W.,
J. Poensgen,
U. Rausch,
H. F. Kern,
and
G. A. Scheele.
Translational control of anionic trypsinogen and amylase synthesis in rat pancreas in response to caerulein stimulation.
Proc. Natl. Acad. Sci. USA
85:
6597-6601,
1988[Abstract].
44.
Takács, T.,
I. Nagy,
A. Pap,
and
V. Varró.
The effect of long-term administration of lorglumide (CR 1409) on rat pancreatic growth and enzyme composition.
Pancreas
5:
606-610,
1990[Medline].
45.
Tybulewicz, V. L.,
C. E. Crawford,
P. K. Jackson,
R. T. Bronson,
and
R. C. Mulligan.
Neonatal Lethality and Lymphopenia in mice with a homozygous disruption of the c-able protooncogene.
Cell
65:
1153-1163,
1991[Medline].
46.
Werlin, S. L.,
S. Virojanavat,
E. Reynolds,
R. G. Hoffman,
and
D. G. Colton.
Effects of cholecystokinin and hydrocortisone on DNA and protein synthesis in immature rat pancreas.
Pancreas
3:
274-278,
1988[Medline].
47.
Wisner, J. R., Jr.,
R. E. McLaughlin,
K. A. Rich,
S. Ozawa,
and
I. G. Renner.
Effects of L-364,718, a new cholecystokinin receptor antagonist, on camostate-induced growth of the rat pancreas.
Gastroenterology
94:
109-113,
1988[Medline].
48.
Wisner, J. R., Jr.,
S. Ozawa,
B. G. Xue,
and
I. G. Renner.
Chronic administration of a potent cholecystokinin receptor antagonist, L-364,718, fails to inhibit pancreas growth in preweanling rats.
Pancreas
5:
434-438,
1990[Medline].
49.
Yule, D. I.,
D. Wu,
T. E. Essington,
J. A. Shayman,
and
J. A. Williams.
Sphingosine Metabolism Induces Ca2+ Oscillations in rat pancreatic acinar cells.
J. Biol. Chem.
268:
12353-12358,
1993
50.
Zavros, Y.,
W. R. Fleming,
K. J. Hardy,
and
A. Shulkes.
Regulation of fundic and antral somatostatin secretion by CCK and gastrin.
Am. J. Physiol.
274 (Gastrointest. Liver Physiol. 37):
G742-G750,
1998
51.
Zucker, K. A.,
T. E. Adrian,
A. J. Bilchik,
and
I. M. Modlin.
Effects of the CCK receptor antagonist L364,718 on pancreatic growth in adult and developing animals.
Am. J. Physiol.
257 (Gastrointest. Liver Physiol. 20):
G511-G516,
1989