The endothelin ETA receptor-specific effect of 50-235, a nonpeptide endothelin antagonist.
We characterized the endothelin receptor antagonist 27-O-caffeoyl myricerone (50-235), isolated from the bayberry Myrica cerifera, using rat aortic smooth muscle A7r5 cells that express ETA receptors and human Girardi heart cells that express ETB receptors. 50-235 concentration-dependently inhibited 125I-ET-1 binding to A7r5 cells with Ki of 51 +/- 12 nM, while it had no effect on 125I-ET-1 and 125I-ET-3 bindings to Girardi heart cells. Also in affinity cross-linking studies with 125I-ET-1, 50-235 inhibited labeling of a protein of M(r) = 67,000 in A7r5 cells, but did not inhibit labeling of two proteins with M(r) values of 70,000 and 46,000 in Girardi heart cells. Functionally, 50-235 inhibited the ET-1-induced increase in cytosolic free Ca2+ concentration ([Ca2+]i) in a dose-dependent manner (IC50 = 11 +/- 2 nM) in A7r5 cells. On the other hand, this compound had no effect on the basal level of [Ca2+]i and the high K(+)- and bombesin-induced increases in [Ca2+]i in A7r5 cells, nor on the ET-1-induced increase in [Ca2+]i in Girardi heart cells. Also, 50-235 inhibited ET-1-promoted mitogenesis of A7r5 cells. Thus, we conclude that 50-235 is a specific endothelin A receptor antagonist that could be very useful for elucidating the physiological and pathophysiological significance of ET.
Mihara
S
S
Shionogi Research Laboratories, Shionogi & Co., Osaka, Japan.
Fujimoto
M
M
D000818:Animals; D001345:Autoradiography; D002109:Caffeic Acids / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D003432:Cross-Linking Reagents; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis; D004591:Electrophoresis, Polyacrylamide Gel; D065128:Endothelin Receptor Antagonists; D016232:Endothelins / Q000378:metabolism / Q000493:pharmacokinetics; D006801:Humans; D007457:Iodine Radioisotopes; D008934:Mitogens / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D051381:Rats
D002109:Caffeic Acids; D003432:Cross-Linking Reagents; D065128:Endothelin Receptor Antagonists; D016232:Endothelins; D007457:Iodine Radioisotopes; D008934:Mitogens; C075745:myriceron caffeoyl ester; D004247:DNA; D011188:Potassium; D002118:Calcium