Stored calcium modulates inositol phosphate synthesis in cultured smooth muscle cells

Cytosolic Ca2+ concentrations ([Ca2+]cyt) and [3H]inositol phosphates ([3H]InsP) were correlated while varying the Ca2+ content of the sarcoplasmic reticulum (SR) in cultured A7r5 cells at rest and during activation with [Arg8]-vasopressin (AVP). Thapsigargin (TG) raised and superfusion with 0 Ca2+ lowered [Ca2+]cyt, but both treatments decreased SR Ca2+ and AVP-evoked Ca2+ transients. Neither TG nor 0 Ca2+ affected basal [3H]InsP, but both treatments increased AVP-evoked synthesis of [3H]InsP. Exposure for several minutes to 40 mM K+ solution, BAY K 8644, or low-Na+ solution all elevated [Ca2+]cyt and, thereby, increased SR Ca2+, as manifested by augmented AVP-evoked Ca2+ transients. In all three cases, AVP-evoked, but not basal, [3H]InsP were reduced. The inhibitory effect of 40 mM K+ on AVP-evoked [3H]InsP synthesis was blocked when SR Ca2+ uptake was prevented by TG. Brief (30-s) exposures to 40 mM K+, which elevated [Ca2+]cyt but not SR Ca2+ loading, did not modify AVP-evoked [3H]InsP synthesis or Ca2+ transients. These results demonstrate an inverse relationship between SR Ca2+ content and evoked [3H]-InsP synthesis. Moreover, they suggest that SR Ca2+ may serve as a signal that modulates sarcolemmal [3H]InsP formation.

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Fatty acid inhibition of angiotensin II-stimulated inositol phosphates in smooth muscle cells

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1993.264.2.h595 ◽

1993 ◽

Vol 264 (2) ◽

pp. H595-H603

Author(s):

M. E. Ullian

Keyword(s):

Smooth Muscle ◽

Angiotensin Ii ◽

Smooth Muscle Cells ◽

Receptor Binding ◽

Inositol Phosphates ◽

Inositol Phosphate ◽

Muscle Cells ◽

Ang Ii ◽

Guanine Nucleotide Binding Protein ◽

Cellular Incorporation

Inositol phosphate (InsP) responses to angiotensin II (ANG II) stimulation were measured in cultured rat vascular smooth muscle cells (VSMC) incubated with and without fatty acids (FA). VSMC were washed after 24 h of FA incubation to achieve cellular incorporation of FA yet eliminate ambient FA. Incubation with eicosapentaenoic acid (EPA)-supplemented medium resulted in concentration-dependent incorporation of EPA and depletion of arachidonic acid in VSMC membranes. Incubation with EPA, but not other FA, resulted in inhibition of ANG II-stimulated InsP formation (29% inhibition with 100 microM EPA). In contrast, InsP formation in response to guanine nucleotide-binding protein stimulation was not affected by EPA. ANG II receptor binding to membranes prepared from EPA-loaded VSMC was 18% lower than binding in membranes from sham-loaded cells. In other studies, VSMC were exposed acutely to FA to avoid cellular incorporation. Exposure to all FA resulted in concentration-dependent reductions in ANG II binding and ANG II-stimulated InsP formation; binding affinity was reduced without changes in receptor density. We conclude that ANG II-stimulated InsP formation is modestly and selectively inhibited by EPA incorporation and more profoundly inhibited by acute exposure to many FA via interference with ANG II receptor binding.

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Ca2+ stores in smooth muscle cells: Ca2+ buffering and coupling to AVP-evoked inositol phosphate synthesis

AJP Cell Physiology ◽

10.1152/ajpcell.1994.266.1.c276 ◽

1994 ◽

Vol 266 (1) ◽

pp. C276-C283 ◽

Cited By ~ 7

Author(s):

D. M. Berman ◽

T. Sugiyama ◽

W. F. Goldman

Keyword(s):

Smooth Muscle ◽

Inverse Relationship ◽

Inositol Phosphates ◽

Inositol Phosphate ◽

Enzyme System ◽

Similar Treatment ◽

A7r5 Cells ◽

Inositol 1,4,5 Trisphosphate ◽

Communication Pathway

Cytosolic Ca2+ concentrations ([Ca2+]cyt) and [3H]inositol phosphates ([3H]InsP) were correlated while decreasing the Ca2+ content of sarcoplasmic reticulum (SR) stores in cultured A7r5 cells at rest and after activation with 8-arginine vasopressin (AVP). Decreasing Ca2+ influx by reducing extracellular Ca2+ or by treatment with verapamil had no effect on resting [Ca2+]cyt but significantly inhibited the AVP-evoked Ca2+ transients (delta Ca2+). Neither treatment affected basal [3H]InsP, but both treatments increased AVP-evoked synthesis of [3H]InsP. Likewise, basal [3H]InsP were unaffected by brief (10-30 s) exposures to thapsigargin (TG), while AVP-induced [3H]InsP synthesis was significantly augmented. Similar treatment with TG rapidly increased resting [Ca2+]cyt and decreased SR Ca2+ by 9-25% as manifested by decreased delta Ca2+. By contrast, ryanodine induced slow increases in [Ca2+]cyt that stabilized within 30 min; subsequent AVP-induced delta Ca2+ were attenuated by 50%. Ryanodine had no effect on either basal or stimulated [3H]InsP levels. Agents that elevate adenosine 3',5'-cyclic monophosphate (cAMP) such as caffeine, 8-bromo-cAMP, and forskolin inhibited AVP-evoked [3H]InsP formation. These observations provide further characterization of a communication pathway between the AVP-sensitive Ca2+ stores in the SR and the plasmalemmal enzyme system involved in the synthesis of inositol 1,4,5-trisphosphate. This pathway is manifested by an inverse relationship between the Ca2+ content of an AVP-sensitive, ryanodine-insensitive SR Ca2+ store and evoked [3H]InsP synthesis and may represent an important component in the tonic regulation of resting [Ca2+]cyt and vasoconstrictor- and hormone-evoked SR Ca2+ release.

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Measurement of Calcium Fluctuations Within the Sarcoplasmic Reticulum of Cultured Smooth Muscle Cells Using FRET-based Confocal Imaging

Journal of Visualized Experiments ◽

10.3791/53912 ◽

2016 ◽

Author(s):

Gabriela Ziomek ◽

Cornelis van Breemen ◽

Mitra Esfandiarei

Keyword(s):

Smooth Muscle ◽

Sarcoplasmic Reticulum ◽

Smooth Muscle Cells ◽

Muscle Cells ◽

Confocal Imaging ◽

Cultured Smooth Muscle Cells

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Effect of Propofol on Arachidonate Cascade by Vasopressin in Aortic Smooth Muscle Cells

Anesthesiology ◽

10.1097/00000542-199901000-00028 ◽

1999 ◽

Vol 90 (1) ◽

pp. 215-224 ◽

Cited By ~ 6

Author(s):

Kumiko Tanabe ◽

Osamu Kozawa ◽

Hiroyuki Matsuno ◽

Masayuki Niwa ◽

Shuji Dohi ◽

...

Keyword(s):

Smooth Muscle ◽

Smooth Muscle Cells ◽

Phospholipase C ◽

Phospholipase D ◽

Inositol Phosphate ◽

Muscle Cells ◽

Inhibitory Effect ◽

Vascular Effects ◽

Aortic Smooth Muscle ◽

Arachidonate Cascade

Background The mechanisms underlying the vascular effects of propofol are not fully understood. Vasopressin, a potent vasoactive peptide, stimulates the arachidonate cascade and the synthesis of prostacyclin (PGI2; the main metabolite of the cascade in vascular smooth muscle cells). Arachidonic acid (AA) release by phospholipases is the rate-limiting step in the cascade. We investigated the mechanisms underlying vasopressin-induced AA release and the effect of propofol on PGI2 synthesis in a rat aortic smooth muscle cell line: A10 cells. Methods In cultured A10 cells pretreated with propofol, the stimulation by vasopressin of AA release and PGI2 synthesis was evaluated by measuring [3H]AA and 6-keto PGF1alpha, respectively, in the culture medium. The effects of propofol on vasopressin-induced activation of phosphoinositide-hydrolyzing phospholipase C and phosphatidylcholine-hydrolyzing phospholipase D were evaluated by measuring inositol phosphate formation and choline formation, respectively. Results A phospholipase C inhibitor and a phosphatidic acid phosphohydrolase inhibitor both attenuated vasopressin-induced AA release and PGI2 synthesis, as did a phospholipase A2 inhibitor. Propofol inhibited vasopressin-induced activation of phosphoinositide-hydrolyzing phospholipase C and phosphatidylcholine-hydrolyzing phospholipase D, but this effect of propofol was significant only at supraclinical concentration (0.1 mM). Propofol reduced vasopressin-induced PGI2 synthesis. The inhibitory effect was observed at concentrations (10 microM-0.1 mM) higher than those used clinically. Conclusions Propofol suppresses the arachidonate cascade caused by vasopressin at least partly by inhibiting phosphoinositide-hydrolyzing phospholipase C and phosphatidylcholine-hydrolyzing phospholipase D, resulting in the inhibition of PGI2 synthesis. Propofol-mediated inhibition of vasopressin-stimulated synthesis of PGI2 may reduce the vasorelaxation by propofol.

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