Participation of protein kinase C in endothelin-1-induced contraction in rat aorta: studies with a new tool, calphostin C.
1. Calphostin C at 10(-6) M was shown to be selective and highly effective in inhibiting contractile responses of rat aortae to 12-o-tetradecanoylphorbol-13-acetate, while it had no effect on contractile responses to elevated KCl. 2. In the rat aorta, endothelin-1 (ET-1) developed a sustained tonic contraction dose-dependently in both normal Ca(2+)-containing Krebs and Ca(2+)-free Krebs containing 1 mM EGTA. Calphostin C (10(-6) M), a selective protein kinase C inhibitor, antagonized the maximal tensions for cumulative addition of 10(-8) M ET-1 by 13.2% in Ca(2+)-containing medium and 25.8% in Ca(2+)-free Krebs containing 1 mM EGTA. 3. In both Ca(2+)-containing medium and Ca(2+)-free Krebs containing 1 mM EGTA, precontraction with 10(-8) M ET-1 had no effects on the contractile response to subsequently added 10(-6) M 12-o-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C. 4. In Ca(2+)-free Krebs containing 1 mM EGTA, precontraction with 10(-6) M TPA potentiated the contractile response to subsequently added 10(-8) M ET-1, whereas this potentiation was abolished by pretreatment with 10(-6) M calphostin C. The mechanism of the TPA-induced potentiating effect remains to be determined. 5. These results suggest that the participation of protein kinase C in the 10(-8) M ET-1-induced contraction may be 13.2% and 25.8% in the presence and absence of extracellular Ca2+, respectively, and that mechanisms other than protein kinase C may be predominantly responsible for ET-1-induced tonic contraction.
Shimamoto
H
H
Department of Biomedical Sciences, Faculty of Health Sciences, McMaster University, Hamilton, Ontario, Canada.
Shimamoto
Y
Y
Kwan
C Y
CY
Daniel
E E
EE
D000818:Animals; D001011:Aorta; D002118:Calcium / Q000494:pharmacology; D016232:Endothelins / Q000494:pharmacology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009281:Naphthalenes; D011083:Polycyclic Compounds / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects*
D016232:Endothelins; D009281:Naphthalenes; D011083:Polycyclic Compounds; D011189:Potassium Chloride; D011493:Protein Kinase C; C058819:calphostin C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium