Regulation of arterial tone by smooth muscle myosin type
II
Matthias
Löhn,
Dietmar
Kämpf,
Chai
Gui-Xuan,
Hermann
Haller,
Friedrich C.
Luft, and
Maik
Gollasch
Franz Volhard Clinic and Max Delbrück Center for
Molecular Medicine, Charité University Hospital, Humboldt
University of Berlin, 13125 Berlin; and Medical School
Hannover, Department of Nephrology, D-30625 Hannover,
Germany
 |
ABSTRACT |
The
initiation of contractile force in arterial smooth muscle (SM) is
believed to be regulated by the intracellular Ca2+
concentration and SM myosin type II phosphorylation. We tested the
hypothesis that SM myosin type II operates as a molecular motor protein
in electromechanical, but not in protein kinase C (PKC)-induced,
contraction of small resistance-sized cerebral arteries. We utilized a
SM type II myosin heavy chain (MHC) knockout mouse model and measured
arterial wall Ca2+ concentration
([Ca2+]i) and the diameter of pressurized
cerebral arteries (30-100 µm) by means of digital fluorescence
video imaging. Intravasal pressure elevation caused a graded
[Ca2+]i increase and constricted cerebral
arteries of neonatal wild-type mice by 20-30%. In contrast,
intravasal pressure elevation caused a graded increase of
[Ca2+]i without constriction in (
/
)
MHC-deficient arteries. KCl (60 mM) induced a further
[Ca2+]i increase but failed to induce
vasoconstriction of (
/
) MHC-deficient cerebral arteries. Activation
of PKC by phorbol ester (phorbol 12-myristate 13-acetate, 100 nM)
induced a strong, sustained constriction of (
/
) MHC-deficient
cerebral arteries without changing [Ca2+]i.
These results demonstrate a major role for SM type II myosin in the
development of myogenic tone and Ca2+-dependent
constriction of resistance-sized cerebral arteries. In contrast, the
sustained contractile response did not depend on myosin and
intracellular Ca2+ but instead depended on PKC. We suggest
that SM myosin type II operates as a molecular motor protein in the
development of myogenic tone but not in pharmacomechanical coupling by
PKC in cerebral arteries. Thus PKC-dependent phosphorylation of
cytoskeletal proteins may be responsible for sustained contraction in
vascular SM.
protein kinase C; pressurized cerebral arteries; phorbol ester; arterial tone; myosin heavy chain; knockout mouse
 |
INTRODUCTION |
CONTRACTION OF SMOOTH
MUSCLE (SM) is based on a sliding-filament mechanism similar to
that of striated muscle. The SM contraction is regulated by
electromechanical as well as by pharmacomechanical coupling mechanisms.
Excitation-contraction coupling by electromechanical mechanisms depends
on the membrane potential and Ca2+ influx through
voltage-gated Ca2+ channels in the plasma membrane, such as
L-type Ca2+ channels (38). In small arteries,
membrane depolarization from
50 to
40 mV increases external
Ca2+ influx, leading to an increase in global intracellular
Ca2+ concentration ([Ca2+]i) and
subsequent activation of the contractile machinery. Lowering [Ca2+]i reverses contraction
(17). Conclusively, force produced by electromechanical
coupling depends on Ca2+ ions surrounding the contractile
filaments. In contrast, Ca2+ ions are believed to play a
minor role in pharmacomechanical coupling. The activation of protein
kinase C (PKC) and other intracellular enzymes seems to play a key role
in force production by many vasoconstrictor hormones (38).
SM contraction exhibits several distinct properties that are not
present in skeletal muscle. For example, the regulation of crossbridges
interaction in SM contraction by Ca2+ seems to be more
complicated than in striated muscle (32). Accordingly,
pharmacomechanical coupling of SM can be induced in
Ca2+-free external solutions, suggesting additional,
Ca2+-independent pathways of SM contraction
(8). We used the SM myosin type II heavy chain (MHC)
knockout mouse to provide evidence that SM myosin type II operates as
the molecular motor protein for depolarization-induced,
Ca2+-dependent constriction of small cerebral arteries,
i.e., in electromechanical coupling. In addition, we show that
PKC-dependent, sustained constriction does not depend on intracellular
Ca2+ and SM myosin type II. We suggest that this
myosin-independent contractile pathway may play a major role in
pharmacomechanical coupling of small, resistance-sized arteries.
 |
MATERIALS AND METHODS |
Cerebral arteries.
Cerebral arteries were obtained from neonatal (+/+) and (
/
)
SM-MHC-deficient mice genotyped after the experiment (30). After decapitation, the brain was removed and quickly transferred to
cold (4°C), oxygenated (95% O2/5% CO2)
physiological salt solution (PSS) of the following composition (in mM):
119 NaCl, 4.7 KCl, 25 NaHCO3, 1.2 KH2PO4, 1.6 CaCl2, 1.2 MgSO4, 0.03 EDTA, and 11 glucose. Thereafter, the cerebral
arteries were dissected from the brain and placed in cold PSS.
Connective tissue was removed. For measurements of intracellular
arterial wall [Ca2+]i, the vessels were
incubated with the Ca2+-sensitive indicator fura 2-AM (5 µM) and pluronic acid (0.005%; wt/vol) for 45 min at room
temperature in oxygenated PSS. After loading with fura 2-AM, the
arteries were cannulated in a chamber on glass canulas on both sides,
allowing an application of hydrostatic pressure to the vessel (for
details, see Refs. 6, 9, 26, 29). [Ca2+]i and diameter were
measured simultaneously by using a conventional spectrometer (dm3000;
SPEX, Edison, NJ) and a videomicroscopic system (Nikon Diaphot,
Düsseldorf, Germany) connected to a personal computer with
appropriate software for detection of changes of vessel diameter (TSE,
Bad Homburg, Germany) (for calibration and details, see Ref.
9). All experiments were performed at 37°C.
Materials and statistics.
Fura 2-AM was purchased from Molecular Probes (Eugene, OR). Stock
solutions (0.25 mM) of fura 2-AM were made using DMSO as the solvent.
All salts and drugs were obtained from Sigma Aldrich (Deisenhofen,
Germany) or Merck (Darmstadt, Germany). High external potassium
solutions were made by iso-osmotic substitution of NaCl with KCl in the
PSS. All values are given as means ± SE. For group comparisons,
paired and unpaired Student' s t-tests or nonparametric Wilcoxon tests were used as appropriate. A value of P < 0.05 was considered statistically significant; n = number of arteries tested.
 |
RESULTS |
Electromechanical coupling.
We first measured intracellular arterial wall
[Ca2+]i and vessel diameter of isolated
cerebral arteries of (+/+) and (
/
) SM-MHC mice at an intravasal
pressure of 10 mmHg. The cerebral arteries of (+/+) and (
/
) SM-MHC
mice showed no macroscopic differences, for instance in diameter or
branching. Figure 1 shows that resting intracellular [Ca2+]i (~100 nM) and
diameter (~80 µm) were not different (P < 0.05). In cerebral arteries of (+/+) SM-MHC mice, an increase in intravasal pressure from 30 to 60 mmHg induced an increase in
[Ca2+]i and decreased vessel diameter
(myogenic constriction) by 20 µm (Figs.
2B and 4B;
P < 0.05). To evaluate electromechanical coupling in
cerebral arteries of (+/+) SM-MHC mice, high concentrations of external
K+ (60 mM) were applied to the arteries and evoked an
increase in [Ca2+]i to ~1,000 nM and an
additional 20% constriction in the vessels of (+/+) SM-MHC mice,
compared with controls (Figs. 2B and 4B; P < 0.05).

View larger version (9K):
[in this window]
[in a new window]
|
Fig. 1.
Comparison of resting intracellular arterial wall Ca2+
(A) and vessel diameter (B) in ( / ) myosin
heavy chain (MHC)-deficient cerebral arteries and (+/+) controls.
Parameters were not significantly different (n 8).
Intravascular pressure was 10 mmHg.
|
|

View larger version (15K):
[in this window]
[in a new window]
|
Fig. 2.
Development of myogenic tone in (+/+) MHC wild-type cerebral
arteries. A: schematic model of myogenic tone development.
Increase in intravascular pressure induces membrane depolarization of
arterial smooth muscle (SM) cells. Depolarization opens
voltage-dependent Ca2+ channels, leading to an increase in
global intracellular Ca2+ concentration (9, 23,
26). The increase in global intracellular Ca2+
activates the contractile apparatus in the cell, leading to an
actin-myosin II interaction and, subsequently, to cell contraction.
B: simultaneous measurement of intracellular arterial wall
Ca2+ and vessel diameter. Intravascular pressure was
increased stepwise from 10 to 60 mmHg. The increase in intravascular
pressure increased arterial wall Ca2+ (upper
trace) and induced myogenic tone (lower trace, decrease
of vessel diameter). Application of 60 mM KCl evoked an additional
increase in arterial wall Ca2+ and induced
vasoconstriction. The presence of KCl is indicated by the horizontal
line.
|
|
In contrast, cerebral arteries of (
/
) SM-MHC mice did not develop
myogenic constriction when intravascular pressure was increased to 30 or to 60 mmHg (Figs. 3B and
4A). Instead, the vessel diameter was "passively"
increased by these maneuvers by 15 to 20% (Fig.
4A; P < 0.05). However, the stepwise increase in intravascular pressure from 10 to 60 mmHg induced a graded increase in
[Ca2+]i up to 200 nM (P < 0.05). High concentrations of external K+ (60 mM) were
applied to the arteries of (
/
) SM-MHC mice to test whether or not
the electromechanical coupling in these arteries was functional.
Application of 60 mM KCl to arteries of (
/
) SM-MHC mice evoked an
increase in [Ca2+]i to ~1,000 nM (Figs.
3B and 4A; P < 0.05). However,
this maneuver did not constrict the vessels (Figs. 3B and
4A; P < 0.05). These findings indicate that
pressure-induced and membrane potential-dependent Ca2+
influx mechanisms are intact in arteries of (
/
) SM-MHC mice (Fig.
3B). However, in sharp contrast to arteries of (+/+) SM-MHC mice, Ca2+-dependent, electromechanical coupling was not
functional in cerebral arteries lacking SM-MHC (Fig. 3B).

View larger version (15K):
[in this window]
[in a new window]
|
Fig. 3.
Lack of myogenic tone and KCl induced vasoconstriction in ( / )
MHC-deficient cerebral arteries. A: proposed schematic model
of absent myogenic tone. B: simultaneous measurement of
arterial wall Ca2+ and vessel diameter. Intravascular
pressure was increased stepwise from 10 to 60 mmHg. This increase
induced a sustained increase in arterial wall Ca2+
(upper trace). However, this increase in Ca2+
did not cause myogenic constriction of the artery (lower
trace). Subsequent application of KCl (60 mM) increased arterial
wall Ca2+ but did not cause vasoconstriction.
|
|

View larger version (13K):
[in this window]
[in a new window]
|
Fig. 4.
Changes in arterial wall Ca2+ and vessel diameter of
( / ) MHC cerebral arteries and (+/+) controls induced by
intravascular pressure and 60 mM KCl. Changes are expressed as a
percentage of steady-state change in arterial wall
[Ca2+]i (arbitrary units in %; 100%) and
steady-state vessel diameter (100%) obtained with 10 mmHg before
administration of 30 mmHg, 60 mmHg, or 60 mM KCl (n 12).
A: arteries of ( / ) SM-MHC mice did not develop the
myogenic response or constricted to 60 mM KCl. B: arteries
of (+/+) SM-MHC mice showed a reduced diameter in response to increased
intravascular tone or KCl.
|
|
PKC-induced constriction.
We next tested the hypothesis that PKC induces pharmacomechanical
coupling in cerebral arteries. In the presence of external Ca2+, the PKC activator phorbol 12-myristate 13-acetate
(PMA, 100-500 nM) induced a strong constriction of arteries of
(+/+) SM-MHC mice (Figs. 5B
and 7B; P < 0.05). PMA did not increase
[Ca2+]i (Figs. 5B and
7B; P > 0.05). The SM constriction induced
by PMA was rapid and reached the maximum (~50-60% constriction)
after 2 min (half-activation time of contraction ~99 s; Fig.
5B). This PMA effect was not attenuated in both nominal
Ca2+-free and Ca2+-buffered [5 mM
N-(2-hydrohyethyl)ethylenediamine-N,N',N'-triacetic acid (HEDTA)] solutions (P > 0.05). These findings
indicate that PKC activation induces a fast, sustained, and relatively
Ca2+-independent induced constriction of cerebral arteries
of (+/+) SM-MHC mice.

View larger version (17K):
[in this window]
[in a new window]
|
Fig. 5.
Effects of phorbol 12-myristate 13-acetate (PMA) on arterial wall
[Ca2+]i and diameter of (+/+) MHC, wild-type
cerebral arteries. A: proposed schematic model of arterial
tone regulation by actin-myosin II interaction and protein kinase C
activation. B: application of external KCl (60 mM) evoked an
increase in arterial wall Ca2+ (upper trace) and
a strong constriction (lower trace). Subsequent application
of PMA (500 nM) induced a rapid vasoconstriction within 2 min
(half-activation time of contraction ~99 s). Arterial wall
Ca2+ was only slightly increased. The constriction was
maintained in nominal Ca2+-free solution (PSS without
CaCl2) and even in strong Ca2+-buffered
[nominal Ca2+-free solution plus 5 mM
N-(2-hydrohyethyl)ethylenediamine-N,N',N'- triacetic
acid (HEDTA)] solution. PMA, external Ca2+-free solutions,
and KCl are indicated by horizontal lines.
|
|
In contrast, PMA (100-500 nM) evoked a delayed constriction of
(
/
) MHC-deficient arteries by ~30% (half-activation time of
contraction ~540 s; Figs. 6,
A and C, and
7A; P < 0.05). PMA did not significantly change
[Ca2+]i (P > 0.05). Removal
of external Ca2+ or strongly buffered Ca2+-free
(5 mM HEDTA) external bath solution did not attenuate the PMA-induced
vessel constriction (Figs. 6C and 7A;
P > 0.05). Subsequent application of external KCl (60 mM) induced an increase in [Ca2+]i to ~1
µM in cerebral arteries of (
/
) SM-MHC mice
(P < 0.05) but did not induce further vessel
constriction (P > 0.05). Cerebral artery constriction
induced by stimulation of PMA was completely inhibited by a 10-min
preincubation with calphostin C (100 nM; data not shown;
n = 3).

View larger version (53K):
[in this window]
[in a new window]
|
Fig. 6.
Effects of PMA on arterial wall [Ca2+]i
and diameter of ( / ) MHC-deficient cerebral arteries. A:
image of a cannulated intact cerebral artery before and after
stimulation of PKC by 500 nM PMA. B: schematic model of
PMA-induced constriction of ( / ) MHC-deficient cerebral arteries.
C: PMA (500 nM) induced a delayed (half-activation time of
contraction ~540 s) and sustained constriction that was not
influenced by removal of external Ca2+ or use of a strong,
buffered, Ca2+-free external solution (HEDTA). Subsequent
60 mM KCl application in normal, Ca2+-containing PSS
solution did not induce a further constriction but solely increased
arterial wall Ca2+ concentration. PMA, external
Ca2+-free solutions, and KCl are indicated by horizontal
lines.
|
|

View larger version (14K):
[in this window]
[in a new window]
|
Fig. 7.
Changes of arterial wall [Ca2+]i and
vessel diameter by PMA (100-500 nM) in ( / ) and (+/+)
MHC-deficient cerebral arteries (n 8). Changes are
expressed as a percentage changes of the steady-state in arterial wall
[Ca2+]i (A: arbitrary units in %,
100%) and steady-state vessel diameter (B: 100%) obtained
before administration of PMA (n 12). A:
application of phorbol ester evoked a ~40% constriction of arteries
of ( / ) SM-MHC mice. The phorbol ester evoked constriction was
maintained in Ca2+-free or Ca2+-buffered bath
solution (A). B: application of phorbol ester
evoked in arteries of (+/+) SM-MHC mice a ~55% vasoconstriction. The
phorbol ester induced constriction did not depend on extracellular
calcium.
|
|
 |
DISCUSSION |
The mechanisms that lead to sustained SM contraction that occurs
in arterial vasospasm and arterial hypertension remain unknown (39). We used the SM-MHC-deficient (
/
) mouse to
characterize excitation-contraction coupling in myogenic cerebral
arteries. Our data suggest that SM-MHC type II operates as a molecular
motor protein in electromechanical coupling but not in
pharmacomechanical coupling mediated by PKC of cerebral arteries.
Electromechanical coupling in cerebral arteries of (+/+) and (
/
)
SM-MHC mice was tested by elevating intravascular pressure to induce
myogenic tone and by application of high potassium chloride (60 mM KCl) (1, 2, 13, 22, 28). Elevated intravasal pressure (60 mmHg)
and application of 60 mM KCl increased
[Ca2+]i and reduced vessel diameter in
cerebral arteries of (+/+) SM-MHC mice. In contrast, arteries of
(
/
) SM-MHC mice did not develop myogenic tone but nevertheless
showed normal Ca2+ transport regulation. Because of normal
pressure- and K+-induced [Ca2+]i
increases in arteries of (
/
) SM-MHC mice, we assume that the
initial step of electromechanical coupling in SM is functional in these
arteries. However, the lack of SM contraction indicates that the
contraction signal could not be converted into force by the contractile
apparatus. The results indicate that other myosin isoforms could not
assume force production in the absence of SM myosin type II. This
finding is contrary to the suggestions by Morano et al.
(30), who studied the urinary bladder of (
/
) SM-MHC
mice (30). They reported that SM strips from urinary bladder of (
/
) MHC mice showed a sustained contraction after high
doses of KCl (60 mM). We failed to observe a fast initial (phase
1) or a delayed (phase 2) contraction in cerebral
artery preparations, as reported for urinary bladder (30).
Morano et al. (30) suggested that nonmuscle myosin assumed
the function of SM myosin type II to induce contraction in (
/
) SM
myosin urinary bladder. However, because we did not observe contraction in (
/
) SM-MHC-deficient mice, it is possible that the complete myosin-actin-dependent contractile machinery is not functional in
vascular SM of (
/
) SM-MHC-deficient cerebral arteries. Moreover, the data demonstrate that SM type II myosin operates a molecular motor
protein in the development of myogenic tone and electromechanical coupling of cerebral arteries (Fig. 8).

View larger version (20K):
[in this window]
[in a new window]
|
Fig. 8.
Proposed model of electromechanical (A) vs.
pharmacomechanical (B) coupling induced by protein kinase C
in cerebral arteries. Electromechanical coupling depends on membrane
potential and opening of voltage-gated Ca2+ channels.
Ca2+ influx from the extracellular space and
Ca2+ release from the internal stores activate the
myosin-actin machinery and lead to contraction of the SM cell.
Ca2+ and SM myosin type II play a major regulatory role in
electromechanical coupling. In contrast, pharmacomechanical coupling
induced by protein kinase C activation is relatively insensitive to
changes of membrane potential and [Ca2+]i. We
suggest that this pathway is mediated by protein kinase C-induced
phosphorylation of an unknown intracellular motor protein. Possible
candidates are a cytoskeletal protein or nonidentified myosin
isoforms.
|
|
PKC-induced arterial constriction of MHC-deficient mice.
Many hormonal vasoconstrictors activate PKC and, thereby, induce
"pharmacomechanical" contraction of arterial SM (10).
Analysis of PKC activation in SM revealed that during this process,
some PKC isoforms translocate to the membrane (11, 12, 19, 20, 21, 24, 37) and are involved in the Ca2+
sensitization of the intact SM (3, 14, 25, 34). As shown by others, PKC activation induces a sustained arterial SM contraction in arteries expressing SM-MHC type II (3, 5, 16, 31, 36)
with a slight (35) or no increase in
[Ca2+]i (15, 40).
We observed also that lowering extracellular Ca2+, by using
nominal Ca2+-free bath solution or strong buffered
Ca2+-free bath solution, did not influence PKC-induced
contraction of wild-type cerebral arteries. Moreover, our results show
that the PKC-induced vessel constriction is still inducible in arteries of (
/
) SM-MHC mice. Thus we suggest that PKC-induced contraction in
cerebral arteries of (+/+) SM-MHC mice may involve two components. The
first is a SM myosin type II-mediated contraction with a fast onset,
within 2 min after PKC stimulation. The second is a contraction mediated by a molecular motor protein other than SM myosin type II,
namely a non-SM-myosin type II motor protein (possibly nonmuscle myosin). The latter molecular motor protein is turned on by PKC in
cerebral arteries with a slow onset, ~15 min after PKC stimulation. According to this model, we observed only the delayed non-SM myosin type II motor protein-mediated constriction with a slow onset (15 min)
in arteries of (
/
) SM-MHC mice. Extracellular Ca2+ is
not necessary to maintain this contractile mechanism.
In this context, it is noteworthy that PKC activation leads to changes
in the cell cytoskeleton in a variety of cells and may represent an
important regulator of cytoskeletal functions (18). Platts
et al. (33) showed that the microtubule network is
involved in arterial SM contraction. Using pharmacological tools, they
induced changes in the vascular SM cell microtubular network and
observed constriction of the vessel without changes in
[Ca2+]i. These effects were not dependent on
the endothelium (33). Thus PKC-dependent phosphorylation
of cytoskeletal proteins may be responsible for sustained contraction
in vascular SM, including those in cerebral arteries of (
/
) SM-MHC
mice (Fig. 8). The cytoskeleton may interact with novel, still
unidentified cytoplasmic proteins to produce contraction. Such proteins
could serve as a substrate for PKC. They should be tightly associated
with the cytoskeleton, and binding should be possibly Ca2+
independent. A short protein with these attributes was recently found
in SM (4, 7, 27).
In conclusion, we provide indirect evidence for a novel molecular motor
protein that is able to induce sustained, Ca2+-independent
contraction of arterial SM. This nonmyosin type II motor protein can be
activated by PKC and seems to play a major role in pharmacomechanical
coupling of arterial SM. Further, SM myosin type II operates as a key
element in the development of myogenic tone and electromechanical
coupling of small, resistance-sized cerebral arteries.
Pharmacomechanical coupling mediated by a nonmyosin type II is of
interest in various pathophysiological conditions, including
hypertension, coronary vasospasm, and migraine. It remains to
characterize the molecular motor, and further studies are needed to
clarify this point.
 |
ACKNOWLEDGEMENTS |
We thank Drs. Ingo Morano and M. Bader, Max Delbrück Center
Berlin, for providing the MHC-deficient mice.
 |
FOOTNOTES |
This work was supported by the Deutsche Forschungsgemeinschaft.
Address for reprint requests and other correspondence: M. Gollasch, Franz Volhard Clinic, Wiltbergstrasse 50, 13125 Berlin, Germany (E-mail: gollasch{at}fvk-berlin.de).
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. Section 1734 solely to indicate this fact.
June 26, 2002;10.1152/ajpcell.01369.2000
Received 12 December 2000; accepted in final form 24 June 2002.
 |
REFERENCES |
1.
Bayliss, WM.
On the local reactions of the arterial wall to changes of internal pressure.
J Physiol
28:
220-231,
1902.
2.
Brayden, JE,
and
Nelson MT.
Regulation of arterial tone by activation of calcium-dependent potassium channels.
Science
256:
532-535,
1992[ISI][Medline].
3.
Chatterjee, M,
and
Tejada M.
Phorbol ester-induced contraction in chemically skinned vascular smooth muscle.
Am J Physiol Cell Physiol
251:
C356-C361,
1986[Abstract/Free Full Text].
4.
Dammeier, S,
Lovric J,
Eulitz M,
Kolch W,
Mushinski JF,
and
Mischak H.
Identification of the smooth muscle-specific protein sm22, as a novel protein kinase C substrate using two-dimensional gel electrophoresis and mass spectrometry.
Electrophoresis
21:
2443-2453,
2000[ISI][Medline].
5.
Danthuluri, NR,
and
Deth RC.
Phorbol ester-induced contraction of arterial smooth muscle and inhibition of
-adrenergic response.
Biochem Biophys Res Commun
125:
1103-1109,
1984[ISI][Medline].
6.
Duling, BR,
Gore RW,
Dacey RG,
and
Damon DN.
Methods for isolation, cannulation, and in vitro study of single microvessels.
Am J Physiol Heart Circ Physiol
260:
H130-H135,
1991[Abstract/Free Full Text].
7.
Fu, Y,
Liu HW,
Forsythe SM,
Kogut P,
McConville JF,
Halayko AJ,
Camoretti-Mercado B,
and
Solway J.
Mutagenesis analysis of human SM22: characterization of actin binding.
J Appl Physiol
89:
1985-1990,
2000[Abstract/Free Full Text].
8.
Gokina, NI,
and
Osol G.
Temperature and protein kinase C modulate myofilament Ca2+ sensitivity in pressurized rat cerebral arteries.
Am J Physiol Heart Circ Physiol
274:
H1920-H1927,
1998[Abstract/Free Full Text].
9.
Gollasch, M,
Wellman GC,
Knot HJ,
Jaggar JH,
Damon DH,
Bonev AD,
and
Nelson MT.
Ontogeny of local sarcoplasmic reticulum Ca2+ signals in cerebral arteries: Ca2+ sparks as elementary physiological events.
Circ Res
83:
1104-1114,
1998[Abstract/Free Full Text].
10.
Griendling, KK,
Tsuda T,
and
Alexander RW.
Endothelin stimulates diacylglycerol accumulation and activates protein kinase C in cultured vascular smooth muscle cells.
J Biol Chem
264:
8237-8240,
1989[Abstract/Free Full Text].
11.
Haller, H,
Maasch C,
Lindschau C,
Brachmann M,
Buchner K,
and
Luft FC.
Intracellular targeting and protein kinase C in vascular smooth muscle cells: specific effects of different membrane-bound receptors.
Acta Physiol Scand
164:
599-609,
1998[ISI][Medline].
12.
Haller, H,
Smallwood JI,
and
Rasmussen H.
Protein kinase C translocation in intact vascular smooth muscle strips.
Biochem J
270:
375-381,
1990[ISI][Medline].
13.
Harder, DR.
Pressure-dependent membrane depolarization in cat middle cerebral artery.
Circ Res
55:
197-202,
1984[Abstract].
14.
Jensen, PE,
Gong MC,
Somlyo AV,
and
Somlyo AP.
Separate upstream and convergent downstream pathways of G-protein- and phorbol ester-mediated Ca2+ sensitization of myosin light chain phosphorylation in smooth muscle.
Biochem J
318:
469-475,
1996[ISI][Medline].
15.
Jiang, M,
and
Morgan KG.
Intracellular calcium levels in phorbol ester-induced contractions of vascular muscle.
Am J Physiol Heart Circ Physiol
253:
H1365-H1371,
1987[Abstract/Free Full Text].
16.
Jiang, MJ,
and
Morgan KG.
Agonist-specific myosin phosphorylation and intracellular calcium during isometric contractions of arterial smooth muscle.
Pflügers Arch
413:
637-643,
1989[ISI][Medline].
17.
Kamm, KE,
and
Stull JT.
Regulation of smooth muscle contractile elements by second messengers.
Annu Rev Physiol
51:
299-313,
1989[ISI][Medline].
18.
Keenan, C,
and
Kelleher D.
Protein kinase C and the cytoskeleton.
Cell Signal
10:
225-232,
1998[ISI][Medline].
19.
Khalil, RA,
Lajoie C,
and
Morgan KG.
In situ determination of [Ca2+]i threshold for translocation of the
-protein kinase C isoform.
Am J Physiol Cell Physiol
266:
C1544-C1551,
1994[Abstract/Free Full Text].
20.
Khalil, RA,
Lajoie C,
Resnick MS,
and
Morgan KG.
Ca2+-independent isoforms of protein kinase C differentially translocate in smooth muscle.
Am J Physiol Cell Physiol
263:
C714-C719,
1992[Abstract/Free Full Text].
21.
Khalil, RA,
and
Morgan KG.
Phenylephrine-induced translocation of protein kinase C and shortening of two types of vascular cells of the ferret.
J Physiol
455:
585-599,
1992[Abstract].
22.
Knot, HJ,
and
Nelson MT.
Regulation of membrane potential and diameter by voltage-dependent K-channels in rabbit myogenic cerebral arteries.
Am J Physiol Heart Circ Physiol
269:
H348-H355,
1995[Abstract/Free Full Text].
23.
Knot, HJ,
and
Nelson MT.
Regulation of arterial diameter and wall [Ca2+] in cerebral arteries of rat by membrane potential and intravascular pressure.
J Physiol
508:
199-209,
1998[Abstract/Free Full Text].
24.
Lee, TS,
Chao T,
Hu KQ,
and
King GL.
Endothelin stimulates a sustained 1,2-diacylglycerol increase and protein kinase C activation in bovine aortic smooth muscle cells.
Biochem Biophys Res Commun
162:
381-386,
1989[ISI][Medline].
25.
Lee, MW,
and
Severson DL.
Signal transduction in vascular smooth muscle: diacylglycerol second messengers and PKC action.
Am J Physiol Cell Physiol
267:
C659-C678,
1994[Abstract/Free Full Text].
26.
Lohn, M,
Gollasch M,
Furstenau M,
Morano I,
Luft FC,
and
Haller H.
Tonic vascular contraction is independent of myosin heavy chain and calcium (Abstract).
Kidney Blood Press Res
22:
189,
1999.
27.
Mack, CP,
Somlyo AV,
Hautmann M,
Somlyo AP,
and
Owens GK.
Smooth muscle differentiation marker gene expression is regulated by rhoA-mediated actin polymerization.
J Biol Chem
276:
341-347,
2000[Abstract/Free Full Text].
28.
Meininger, GA,
and
Davis MJ.
Cellular mechanisms involved in the vascular myogenic response.
Am J Physiol Heart Circ Physiol
263:
H647-H659,
1992[Abstract/Free Full Text].
29.
Miller, FJ,
Dellsperger KC,
and
Gutterman DD.
Myogenic constriction of human coronary arterioles.
Am J Physiol Heart Circ Physiol
273:
H257-H264,
1997[Abstract/Free Full Text].
30.
Morano, I,
Chai GX,
Baltas LG,
Lamounier-Zepter V,
Lutsch G,
Kott M,
Haase H,
and
Bader M.
Smooth-muscle contraction without smooth-muscle myosin.
Nat Cell Biol
2:
371-375,
2000[ISI][Medline].
31.
Morgan, KG,
and
Leinweber BD.
PKC-dependent signalling mechanisms in differentiated SM.
Acta Physiol Scand
164:
485-505,
1998.
32.
Murphy, RA.
Contraction in smooth muscle cells.
Annu Rev Physiol
51:
275-283,
1989[ISI][Medline].
33.
Platts, SH,
Falcone JC,
Holton WT,
Hill MA,
and
Meiniger GA.
Alteration of microtubule polymerization modulates arteriolar vasomotor protein tone.
Am J Physiol Heart Circ Physiol
277:
H100-H106,
1999[Abstract/Free Full Text].
34.
Rasmussen, H,
Kojima I,
Kojima K,
Zawalich W,
and
Apfeldorf W.
Calcium as intracellular messenger: sensitivity modulation, C-kinase pathway, and sustained cellular response.
Adv Cyclic Nucleotide Protein Phosphorylation Res
18:
159-193,
1984[ISI][Medline].
35.
Rembold, CM,
and
Murphy RA.
[Ca2+]-dependent myosin phosphorylation in phorbol diester stimulated smooth muscle contraction.
Am J Physiol Cell Physiol
255:
C719-C723,
1988[Abstract/Free Full Text].
36.
Singer, HA,
and
Baker KM.
Calcium dependence of phorbol 12,13-dibutyrate-induced force and myosin light chain phosphorylation in arterial smooth muscle.
J Pharmacol Exp Ther
243:
814-821,
1987[Abstract].
37.
Singer, HA,
Schworer CM,
Sweeley C,
and
Benscoter H.
Activation of protein kinase C isozymes by contractile stimuli in arterial smooth muscle.
Arch Biochem Biophys
299:
320-329,
1992[ISI][Medline].
38.
Somlyo, AP,
and
Somlyo AV.
Signal transduction and regulation in smooth muscle.
Nature
372:
231-236,
1994[ISI][Medline].
39.
Throckmorton, DC,
Packer CS,
and
Brophy CM.
Protein kinase C activation during Ca2+-independent vascular smooth muscle contraction.
J Surg Res
78:
48-53,
1998[ISI][Medline].
40.
Walsh, MP,
Andrea JE,
Allen BG,
Clement-Chomienne O,
Collins EM,
and
Morgan KG.
Smooth muscle protein kinase C.
Can J Physiol Pharmacol
72:
1392-1399,
1994[ISI][Medline].
Am J Physiol Cell Physiol 283(5):C1383-C1389
0363-6143/02 $5.00
Copyright © 2002 the American Physiological Society