Role of protein kinase C in the endothelin-induced contraction in the rabbit saphenous vein.
The role of protein kinase C in the endothelin-induced contraction was examined in the isolated rabbit saphenous vein in which endothelin-1, endothelin-3, sarafotoxin S6c and IRL 1620 (succinyl-[Glu9,Ala11,15]endothelin-1-(8-21))-induced contraction at the threshold concentrations of 0.1-1 pM. A selective inhibitor of protein kinase C, 500 nM calphostin C (2-[12-[2-(benzyloxy)propyl]-3, 10-dihydro-4,9-dihydroxy-2,6,7,11-tetramethoxy-3, 10-dioxo-1-perylenyl]-1-methylethyl carbonic acid 4-hydroxyphenyl ester), shifted the concentration-response curves for these agonists to the right 7.4- to 109-fold. In the vein in which the endothelin ETB receptor was desensitized, sarafotoxin S6c and IRL 1620 were ineffective whereas endothelin-1 and higher concentrations of endothelin-3 induced contractions by activating the endothelin ET(A) receptor. Calphostin C (500 nM) shifted the concentration-response curves for endothelin-1 and endothelin-3 to the right more than 155-fold. Down-regulation of protein kinase C (by treatment with phorbol 12-myristate 13-acetate for 20 h) shifted the concentration-response curves for these agonists to the right before and after desensitization of the endothelin ETB receptor 3.7- to 59-fold. In the permeabilized smooth muscle, Ca(2+)-induced contraction was enhanced by endothelin-1, endothelin-3 and sarafotoxin S6c at concentrations much higher than those needed to induce contraction (threshold concentration was 3 nM). Calphostin C and down-regulation of protein kinase C shifted the concentration-response curves for endothelin-1 and endothelin-3 to the right and downwards without changing the effect of sarafotoxin S6c. In the permeabilized muscle in which the endothelin ETB receptor was desensitized, endothelin-1 and endothelin-3 still augmented the Ca(2+)-induced contraction. Calphostin C and down-regulation of protein kinase C shifted the concentration-response curves for endothelin-1 and endothelin-3 to the right and downwards. These results suggest that protein kinase C is involved in the contraction mediated by the endothelin ET(A) and ETB receptors; and Ca2+ sensitization mediated by the endothelin ET(A) receptor is due to activation of protein kinase C whereas Ca2+ sensitization mediated by the endothelin ETB receptor may be due not only to the activation of protein kinase C but also to other mechanisms.
Sudjarwo
S A
SA
Department of Veterinary Pharmacology, University of Tokyo, Japan.
Karaki
H
H
D000818:Animals; D015536:Down-Regulation / Q000187:drug effects; D016232:Endothelins / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000201:enzymology*; D009281:Naphthalenes / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D011817:Rabbits; D017466:Receptors, Endothelin / Q000187:drug effects / Q000378:metabolism; D012501:Saphenous Vein / Q000187:drug effects / Q000201:enzymology*; D015398:Signal Transduction / Q000187:drug effects
D016232:Endothelins; D004791:Enzyme Inhibitors; D009281:Naphthalenes; D017466:Receptors, Endothelin; D011493:Protein Kinase C; C058819:calphostin C