scholarly journals Mechanism of cellular effect of phorbol esters on action of arginine vasopressin and angiotensin II on rat vascular smooth muscle cells in culture

1988 ◽  
Vol 254 (3) ◽  
pp. 625-629 ◽  
Author(s):  
C Caramelo ◽  
P Tsai ◽  
R W Schrier
Keyword(s):  
Smooth Muscle ◽  
Protein Kinase C ◽  
Angiotensin Ii ◽  
Protein Kinase ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vascular Smooth Muscle Cells ◽  
Arginine Vasopressin ◽  
Muscle Cells ◽  
Kinase C

The inhibitory effect of phorbol-12-myristate-13-acetate (PMA) on the Ca2+-mobilization mechanisms by arginine vasopressin (AVP) and angiotensin II (AII) was analysed in rat vascular smooth muscle cells (VSMC) in culture. PMA inhibited the Ca2+-mobilizing effect of both AVP and AII in a dose-dependent manner, including the rise in cytosolic free Ca2+ ([Ca2+]i) and Ca2+ efflux. In addition, inositol trisphosphate (IP3) production induced by AVP or AII was more than 50% reduced by PMA. The involvement of protein kinase C was implicated by the diminution of the PMA effect by the specific protein kinase C inhibitor isoquinoline-sulphonyl-O-2-methylpiperazine (H7) and the lack of effect of an inactive phorbol. Thus, these results suggest that there is a blocking site that is common or similar for both AVP and AII signal transduction, and that it is a substrate for protein kinase C. This blocking action of protein kinase C occurred at least in part by inhibition of IP3 production and, subsequently, a reduction in cytosolic Ca2+ release. In the presence of ionomycin, which produces an increase in [Ca2+]i that is not altered by PMA, 45Ca2+ efflux was increased instead of inhibited by PMA, thus suggesting that protein kinase C activation also stimulates a Ca2+-extrusion mechanism in VSMC.

scholarly journals Angiotensin II-induced phosphatidylcholine hydrolysis in cultured vascular smooth-muscle cells. Regulation and localization

1991 ◽  
Vol 276 (1) ◽  
pp. 19-25 ◽  
Author(s):  
B Lassègue ◽  
R W Alexander ◽  
M Clark ◽  
K K Griendling
Keyword(s):  
Smooth Muscle ◽  
Protein Kinase C ◽  
Angiotensin Ii ◽  
Protein Kinase ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vascular Smooth Muscle Cells ◽  
Muscle Cells ◽  
Kinase C ◽  
Hydrolysis Of

In cultured vascular smooth-muscle cells (VSMC), angiotensin II (AngII) induces a biphasic, sustained increase in diacylglycerol (DG) of unclear origin. To determine whether hydrolysis of phosphatidylcholine (PC) is a possible source of DG, we labelled cellular PC with [3H]choline, and measured the formation of intra- and extra-cellular [3H]choline and [3H]phosphocholine after stimulation with AngII. AngII induced a concentration-dependent release of choline from VSMC that was significant at 2 min and was sustained over 20 min. In contrast, accumulation of choline inside the cells was very slight. AngII also increased the formation of [3H]myristate-labelled phosphatidic acid, and, in the presence of ethanol, of [3H]phosphatidylethanol, characteristic of a phospholipase D (PLD) activity. Extracellular release of choline was partially inhibited by removal of extracellular Ca2+ (54 +/- 9% inhibition at 10 min) or inhibition of receptor processing by phenylarsine oxide (79 +/- 8% inhibition at 20 min). The protein kinase C activator phorbol myristate acetate also stimulated a large release of choline after a 5 min lag, which was unaffected by the Ca2+ ionophore ionomycin, but was additive with AngII stimulation. Down-regulation of protein kinase C by a 24 h incubation with phorbol dibutyrate (200 nM) decreased basal choline release, but had no effect on AngII stimulation. We conclude that AngII induces a major PC hydrolysis, probably mainly via PLD activation. This reaction is partially dependent on Ca2+ and is independent of protein kinase C, and appears to be mediated by cellular processing of the receptor-agonist complex. Our results are consistent with a preferential hydrolysis of PC from the external leaflet of the plasmalemma, and raise the possibility that PC hydrolysis occurs in specialized ‘signalling domains’ in VSMC.

Mechanisms of rapid desensitization to arginine vasopressin in vascular smooth muscle cells

1991 ◽  
Vol 260 (1) ◽  
pp. F46-F52 ◽  
Author(s):  
C. Caramelo ◽  
P. Tsai ◽  
K. Okada ◽  
V. A. Briner ◽  
R. W. Schrier
Keyword(s):  
Smooth Muscle ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vascular Smooth Muscle Cells ◽  
Arginine Vasopressin ◽  
Muscle Cells ◽  
Receptor Internalization ◽  
Kinase C

This study characterized the rapid desensitization induced by arginine vasopressin (AVP) in vascular smooth muscle cells (VSMC) in culture. The Ca2+ mobilization response and, in some experiments, the intracellular pH changes were used as a probe for the desensitization phenomenon. In VSMC, AVP desensitization was homologous, concentration dependent, and occurred in less than 30 s. The desensitization was complete with 10(-7) M AVP. Receptor occupancy was a critical factor in the maintenance of desensitization, since complete hormone washing by acid glycine buffer produced an earlier (less than 5 min) recovery of the cell response, whereas partial hormone washing with saline (pH 7.4) required 15 min to produce any significant recovery. Protein kinase C activation was a significant mechanism in AVP desensitization, because protein kinase C downregulation inhibited the desensitization phenomenon. Receptor internalization was, however, not important for the desensitization phenomenon, since it still occurred at 4 degrees C. Treatment with pertussis toxin did not affect the Ca2+ mobilization response but decreased the AVP-mediated intracellular alkalinization, therefore suggesting that a Gi or Go protein may be involved in some but not all the aspects of the AVP signal transduction and the desensitization phenomena.

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