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Vasopressin‐stimulated [ 3 H]‐inositol phosphate and [ 3 H]‐phosphatidylbutanol accumulation in A10 vascular smooth muscle cells
Author(s) -
Plevin Robin,
Stewart Allison,
Paul Andrew,
Wakelam Michael J.O.
Publication year - 1992
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1992.tb14471.x
Subject(s) - vasopressin , phospholipase c , inositol , medicine , vasopressin receptor , vascular smooth muscle , endocrinology , protein kinase c , inositol phosphate , chemistry , inositol trisphosphate , phospholipase d , activator (genetics) , biology , receptor , biochemistry , kinase , signal transduction , antagonist , smooth muscle
1 The characteristics of vasopressin‐stimulated phosphatidylinositol 4,5 bisphosphate (PtdIns(4,5)P 2 ) and phosphatidylcholine (PtdCh) hydrolysis were examined in A10 vascular smooth muscle cells (VSMC), by assessing the formation of [ 3 H]‐inositol phosphates ([ 3 H]‐IP) and the accumulation of the phospholipase D (PLD) specific product, [ 3 H]‐phosphatidylbutanol ([ 3 H]‐PtdBuOH). 2 Vasopressin ([Arg 8 ]‐VP) and a number of related analogues stimulated the accumulation of [ 3 H]‐IP and [ 3 H]‐PtdBuOH with similar EC 50 values, generating the same rank order of potency for each response (Arg 8 ‐VP = vasotocin = Lys 8 ‐VP ≫ oxytocin). 3 Inhibition of vasopressin‐stimulated [ 3 H]‐IP and [ 3 H]‐PtdBuOH accumulation by the V 1a receptor antagonists, Des‐Gly 9 [β‐mercapto‐β,β,‐cyclopentamethylene propionyl, O‐Et‐Tyr 2 ,Val 4 ,Arg 8 ]‐vasopressin generated similar IC 50 values suggesting that both these responses are mediated through the activation of a single V 1a receptor subtype. 4 The onset of vasopressin‐stimulated inositol‐1,4,5‐trisphosphate (Ins(1,4,5)P 3 ) mass formation proceeded [ 3 H]‐PtdBuOH accumulation indicating that PtdCh hydrolysis was activated subsequent to PtdIns(4,5)P 2 breakdown. 5 The protein kinase C (PKC) activator, tetradecanoylphorbol acetate (TPA) also stimulated [ 3 H]‐PtdBuOH accumulation. Preincubation with the PKC inhibitor Ro‐31–8220 abolished both TPA‐ and vasopressin‐stimulated [ 3 H]‐PtdBuOH, suggesting that the intermediate activation of protein kinase C is involved in the regulation of PLD by vasopressin. 6 Pretreatment of the A10 VSMC with Ro‐31–8220 (100 μ m ) also potentiated vasopressin‐stimulated Ins(1,4,5)P 3 mass formation. Therefore stimulation of PKC may have opposing roles in the regulation of agonist activation of PLC and PLD. 7 Preincubation of the cells with EGTA, verapamil, or the receptor‐operated calcium channel antagonist, SK&F 96365, reduced vasopressin‐stimulated [ 3 H]‐PtdBuOH accumulation by approximately 30%, suggesting that influx of calcium has a significant role to play in the regulation of vasopressin‐stimulated PLD activity.