DIRECT EVIDENCE FOR AN ANGIOTENSIN AT(1) RECEPTOR-TYPE IN RAT VAS-DEFERENS

Physiological experiments suggest that the angiotensin AT(1) receptor type predominates in rat vas deferens. Membrane binding experiments, u sing I-125-[Sar(1),IIe(8)]angiotensin II, confirm the presence of angi otensin AT(1) receptors and the absence of angiotensin AT(2) receptors in this tissue. Angiotensin II and the angiotensin AT(1) receptor-spe cific antagonist, losartan, bind to rat vas deferens membranes with co mparable affinity, with K-D equal to 22.7 and 34.1 nM, respectively. T he affinities of angiotensin AT(2) receptor-specific ligands are 3 ord ers of magnitude lower. According to the numbers of binding sites and Western blotting of membrane proteins, the concentration of angiotensi n AT(1) receptors in the rat vas deferens is rather low. The fact that similar numbers of binding sites were obtained from binding data for angiotensin II and losartan further supports the hypothesis of exclusi ve existence of angiotensin AT(1) receptor type in rat vas deferens. ( C) 1998 Elsevier Science B.V. All rights reserved.