Characterization of vasopressin receptor in rat lung

This study characterized rat lung membrane arginine vasopressin (AVP) receptors in detail. Specific binding of [³H]AVP to rat lung membranes was dependent upon time, temperature and membrane protein concentration. 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 [³H]AVP binding showed that neurohypophysial hormones as well as their synthetic analogues displaced [³H]AVP in a concentration-dependent manner. The order of potencies for the native peptides was: AVP > lysine vasopressin = arginine vasotocin > oxytocin. Furthermore, potent V(1A) receptor antagonists, d(CH₂)₅Tyr(Me)AVP and dPTyr(Me)AVP, showed high affinity for lung membranes. In contrast, the V₂ receptor agonist, dDAVP, and the specific oxytocin receptor agonist, [Thr⁴,Gly⁷]oxytocin, did not affect AVP binding. These results suggest that the lung contains the V(1A) receptor subtype. The lung membrane AVP receptor characterized in this study may play an important role in mediating the physiological effects of AVP in the lung.