Vascular effects and mechanism of action of endothelin-1 in isolated perfused pig skin.

We investigated the vascular effects and mechanism of action of endothelin-1 (ET-1) in the skin by intra-arterial infusion of ET-1 and its precursor Big ET-1 via a direct cutaneous artery in isolated perfused pig skin flaps (6 x 16 cm). The vascular contractivity was studied by monitoring the perfusion pressure in the skin flap. There was evidence to indicate local conversion of Big ET-1 to ET-1 in the pig skin. It was also observed that ET-1 was a potent long-lasting vasoconstrictor with a potency of approximately 10- and 300-fold higher than those of Big ET-1 and norepinephrine, respectively. The vasoconstrictor action of ET-1 was blocked (P < 0.01) by a selective ETA-receptor antagonist (BQ-123 or BQ-610; 10(-7) M) and enhanced (P < 0.05) by a nitric oxide synthase inhibitor (NG-monomethyl-L-arginine or N omega-nitro-L-arginine methyl ester; 10(-5) M). ET-1-induced increase in perfusion pressure was attenuated (P < 0.05) by an L-type Ca(2+)-channel antagonist (nitrendipine, verapamil, or nifedipine; 10(-5) M) and by removal of Ca2+ from the perfusate. ET-1-induced increase in perfusion pressure was also attenuated (P < 0.05) by a phospholipase C inhibitor (neomycin; 10(-2) M), a protein kinase C (PKC) inhibitor (chelerythrine or H-7; 10(-5) M), and an intracellular Ca2+ chelator [1,2-bis(2-aminophenoxy)]ethane-N,N,N',N'-tetraacetic acid (BAPTA); 10(-5) M]. Furthermore, it was observed that the concentration-dependent (5 x 10(-8) to 10(-5) M) increase in perfusion pressure induced by phorbol 12,13-dibutyrate, a PKC activator, was not affected by verapamil (10(-5) M) or removal of Ca2+ from the perfusate. Taken together, these observations suggest that the vasoconstrictor mechanism of ET-1 in the pig skin involved activation of ETA receptors, L-type Ca2+ channels, phospholipase C, and PKC and that the vasoconstrictor effect caused by activation of PKC was independent of L-type Ca2+ channels.