CHARACTERIZATION OF VASOPRESSIN RECEPTOR IN RAT LUNG

This study characterized rat lung membrane arginine vasopressin (AVP) receptors in detail. Specific binding of [H-3]AVP to rat lung membrane s was dependent upon time, temperature and membrane protein concentrat ion. Scatchard plot analysis of equilibrium binding data revealed the existence of a single class of high-affinity binding sites with a K-d of 0.45 nM and a B-max of 76.6 fmol/mg protein. Competitive inhibition of [H-3]AVP binding showed that neurohypophysial hormones as well as their synthetic analogues displaced [H-3]AVP in a concentration-depend ent manner. The order of potencies for the native peptides was: AVP > lysine vasopressin = arginine vasotocin > oxytocin. Furthermore, poten t V-1A receptor antagonists, d(CH2)(5)Tyr(Me)AVP and dPTyr(Me)AVP, sho wed high affinity for lung membranes. In contrast, the V-2 receptor ag onist, dDAVP, and the specific oxytocin receptor agonist, [Thr(4),Gly( 7)]oxytocin, did not affect AVP binding. These results suggest that th e lung contains the V-1A receptor subtype. The lung membrane AVP recep tor characterized in this study may play an important role in mediatin g the physiological effects of AVP in the lung.