Specific receptor for endothelin in cultured rat cardiocytes.
Specific binding sites for the endothelium-derived vasoconstrictor endothelin (ET) and its effect on cytosolic free Ca2+ concentrations [( Ca2+]i) were studied in a primary culture of cardiocytes from neonatal rats. Binding studies using 125I-labeled-porcine ET as a radioligand revealed the presence of a single class of high-affinity binding sites for ET in cardiocytes with an apparent Kd of 6-9 x 10(-10) M and a Bmax of 50,000-80,000 sites/cell. Neither various vasoconstrictors nor Ca2+-channel blockers affected the binding. Pretreatment with ET substantially reduced the total number of ET receptors without changing their affinity. ET dose-dependently increased [Ca2+]i in fura-2-loaded cardiocytes. These data indicate that cardiocytes have specific ET receptors that are controlled by a down-regulation mechanism, and that ET induces a receptor-mediated increase in [Ca2+]i in cardiocytes.
Hirata
Y
Y
Second Department of Internal Medicine, Tokyo Medical and Dental University, Japan.
Fukuda
Y
Y
Yoshimi
H
H
Emori
T
T
Shichiri
M
M
Marumo
F
F
D000818:Animals; D000831:Animals, Newborn; D001572:Benzofurans; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D016232:Endothelins; D004730:Endothelium, Vascular; D005456:Fluorescent Dyes; D016257:Fura-2; D007457:Iodine Radioisotopes; D007700:Kinetics; D009206:Myocardium / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*; D017466:Receptors, Endothelin; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D001572:Benzofurans; D002121:Calcium Channel Blockers; D016232:Endothelins; D005456:Fluorescent Dyes; D007457:Iodine Radioisotopes; D010455:Peptides; D011956:Receptors, Cell Surface; D017466:Receptors, Endothelin; D014662:Vasoconstrictor Agents; D002118:Calcium; D016257:Fura-2