ENDOTHELIN ETB RECEPTORS SHOW DIFFERENT BINDING PROFILES IN INTACT-CELLS AND CELL-MEMBRANE PREPARATIONS

We examined the affinity of endothelin-l, endothelin-3 and four endoth elin receptor ligands, BQ788 dimethylpiperidinocarbonyl-gamma-methyl-l eu-D-Trp( 1-CO2CH3-D-Nle-ONa), SE-209670 hoxyphenyl)-1-(3,4-methylened ioxyphenyl)-5-(prop-1 -yloxy)indane-2-carboxylic acid), IRL-1620 (succ inyl-[Glu(9),Ala(11,15)]endothelin-1(8-21)), and L-749329 oxyphenoxy)- N-(4-isopropyl-phenylsulfonyl)-benzene acetamide), for endothelin ETB receptors in human and rat heart cells. The affinities of these ligand s showed good correlation between both types of living cells and betwe en their membrane preparations (r = 0.861, P < 0.001), but less signif icant correlation between each of the living cells and its respective membrane preparation (r = 0.569, 0.02 < P < 0.05). These results sugge st that there is no species difference in the affinities of these liga nds and that destruction of the intact cell membrane structure may lea d to changes in binding properties of the endothelin ETB receptor. (C) 1998 Elsevier Science B.V.