ENDOTHELIN-1 IN HUMAN SKIN - IMMUNOLOCALIZATION, RECEPTOR-BINDING, MESSENGER-RNA EXPRESSION, AND EFFECTS ON CUTANEOUS MICROVASCULAR ENDOTHELIAL-CELLS

Endothelin-1 (ET-1), a potent vasoconstrictor peptide, has been implicated in the maintenance of systemic and peripheral vascular tone. We have therefore sought direct evidence of a role for ET-1 in the regulation of blood flow and vascular tone in the human cutaneous microvasculature. Immunostaining for ET-1 was observed in all cutaneous blood vessels of normal human skin including the capillaries of the dermal papillae. Autoradiography showed specific binding of I-125-ET-1 over capillaries and larger blood vessels as well as hair follicles and sweat glands. In situ hybridization with a P-32-labeled RNA probe for ET-1 demonstrated mRNA for ET-1 in cultured human dermal microvascular endothelial cells (HDMEC). In HDMEC, basal release of PGE2 was significantly attenuated by ET-1 (100 pM - 100 nM) (p < 0.05, n = 7) with maximum inhibition in cells incubated with 10 nM ET-1. ET-1 also increased intracellular cAMP in a dose-dependent manner with a significant increase in HDMEC incubated with 100 nM ET-1 (p < 0.05, n = 4). In HDMEC incubated with 100 nM ET-1, inhibition of PGE2 release was unaffected by the dihydropyridine Ca++ channel antagonist nifedipine or the extracellular Ca++ chelator EGTA, whereas the intracellular Ca++ chelator TMB-8 partially blocked the action of ET-1. In contrast, cAMP accumulation was significantly attenuated by EGTA (p < 0.05, n = 4), nifedipine (p < 0.05, n = 4), and TMB-8 (p < 0.05, n = 4), indicating that the endothelial cell responses to ET-1 are complex and appear to involve both Ca++-sensitive and -insensitive pathways. These results provide evidence of an autocrine/paracrine role for ET-1 in the human cutaneous microvasculature.