Modesti P A, Vanni S, Paniccia R, Bandinelli B, Bertolozzi I, Polidori G, Sani G, Neri Serneri G G
Clinica Medica e Cardiologia, University of Florence, Italy.
J Cardiovasc Pharmacol. 1999 Sep;34(3):333-9. doi: 10.1097/00005344-199909000-00003.
On cardiac membranes and isolated cardiomyocytes from the human heart, cell-type distribution and functional activities of endothelin-1 (ET-1) receptor subtypes were investigated by using binding methods and messenger RNA (mRNA) in situ hybridization. The ET-receptor antagonist BMS-182874 selectively and competitively inhibits ET(A) receptors both on isolated myocytes and ventricular membranes with approximately 1,300 times greater affinity for ET(A) than ET(B) subtypes. The [125I]-ET-1 specific binding revealed 42.851+/-2,546 receptors/myocyte with a prevalent proportion of ET(A)-receptor subtypes on both myocytes (84+/-2%) and ventricular membranes (66+/-3%). In situ hybridization studies revealed that mRNA for ET(A) receptors was expressed on both myocytes and nonmyocyte cells, whereas mRNA for ET(B) receptors was almost exclusively expressed on fibroblasts and endothelial cells. Specific binding of [125I]-ET-1 to both myocytes and ventricular membranes in the presence of specific ET(A) (BMS-182874) and ET(B) (BQ-788)-receptor antagonists showed a displacement of [125I]-ET-1 by unlabeled ET-1, which were significantly faster from ET(B) than from ET(A). This suggests a clearance function of ventricular ET(B) receptors.
采用结合方法和信使核糖核酸（mRNA）原位杂交技术，研究了人心脏心肌膜及分离的心肌细胞中内皮素-1（ET-1）受体亚型的细胞类型分布和功能活性。ET受体拮抗剂BMS-182874对分离的心肌细胞和心室膜上的ET(A)受体具有选择性和竞争性抑制作用，其对ET(A)受体的亲和力比对ET(B)亚型高约1300倍。[125I]-ET-1特异性结合显示，每个心肌细胞有42851±2546个受体，ET(A)受体亚型在心肌细胞（84±2%）和心室膜（66±3%）中均占优势。原位杂交研究表明，ET(A)受体的mRNA在心肌细胞和非心肌细胞中均有表达，而ET(B)受体的mRNA几乎仅在成纤维细胞和内皮细胞中表达。在存在特异性ET(A)（BMS-182874）和ET(B)（BQ-788）受体拮抗剂的情况下，[125I]-ET-1与心肌细胞和心室膜的特异性结合显示，未标记的ET-1可使[125I]-ET-1发生位移，ET(B)受体的位移速度明显快于ET(A)受体。这表明心室ET(B)受体具有清除功能。
