Endothelin-1 in human skin: immunohistochemical, receptor binding, and functional studies

The morphological distribution of endothelin-1 (ET-1) was investigated in human digital skin biopsies by immunohistochemistry using endothelin antisera, and by in vitro autoradiographic binding studies with 125I-labeled ET-1. In vitro studies on the responsiveness of cutaneous microvascular endothelium were carried out using human dermal microvascular endothelial cells (HDMEC) cultured from neonatal foreskin. Endothelin immunoreactivity was present in the endothelial cells of cutaneous blood vessels, in large and small arteries, veins in the dermis and capillaries, including those of the dermal papillae. Autoradiographic studies showed the presence of 125I-labeled ET-1 binding sites on the blood vessels and sweat glands. In confluent monolayers of HDMEC, ET-1 (100 pM-100 nM) significantly inhibited basal release of prostaglandin E2 (PGE2) (p less than 0.05), while causing a dose-dependent increase of intracellular cyclic adenosine monophosphate (cAMP) levels. cAMP accumulation, induced by 100 nM ET-1, was blocked by extracellular Ca2+ chelator EGTA, the intracellular Ca2+ chelator TMB-8, and dihydropyridine Ca(2+)-channel antagonist nifedipine (p less than 0.05), whereas ET-1 inhibition of PGE2 release was unaffected. These findings indicate that ET-1 may be important in the control of blood flow and vascular tone in the cutaneous microvasculature.