title: Effects of N-ethylmaleimide on arginine vasopressin-induced responses in an established smooth muscle cell line.
abstract: We have previously reported that 8-arginine vasopressin (AVP) stimulates phosphatidylinositol turnover and Ca++ mobilization in rat aortic smooth muscle cells (A10). In the present study, N-ethylmaleimide (NEM) was used to further characterize the putative guanine nucleotide binding protein that transduces the V1 receptor effects on phosphatidylinositol turnover and Ca++ efflux in these cells. Pretreatment of the cells with low concentrations of NEM did not affect the basal levels of the inositol phosphates and Ca++ efflux but significantly inhibited the AVP-induced increases. NEM pretreatment did not significantly affect [3H]AVP binding to intact cells. Guanyl-5'-yl imidodiphosphate reduced the apparent binding affinity of AVP to cell membranes. NEM pretreatment abolished this guanyl-5'-yl imidodiphosphate effect. AVP stimulated a specific GTPase activity in cell membranes; this effect was also abolished by NEM pretreatment. The results suggest that in A10 cells a guanine nucleotide binding protein sensitive to NEM couples vasopressin receptors to phospholipase C.
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic; D001127:Arginine Vasopressin / Q000031:analogs & derivatives / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D005033:Ethylmaleimide / Q000494:pharmacology*; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism*; D051381:Rats
chemical_list: D010716:Phosphatidylinositols; D001127:Arginine Vasopressin; D006165:Guanylyl Imidodiphosphate; C050890:1-((beta-mercapto-beta)beta cyclopentamethylenepropionic acid)-2-(O-ethyl-Tyr)-4-Val-9-des-Gly-arginine vasopressin; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D005033:Ethylmaleimide; D002118:Calcium