Renal and peripheral vascular responsiveness to arginine vasotocin in bullfrog, Rana catesbeiana.

Arginine vasotocin (AVT), the amphibian neurohypophysial hormone, has pressor and antidiuretic actions in bullfrogs (Rana catesbeiana). Much higher doses of exogenous AVT were required for the pressor response than those for the antidiuretic response. When bullfrog legs and kidneys were perfused under constant pressure simultaneously, the kidney vasculature was more sensitive to bolus injection of AVT than was the leg vasculature. The same was true when the tissues were perfused with different concentrations of hormone. AVT constricts preglomerular vessels in the bullfrog. We suggest that the preglomerular vasculature of the bullfrog is more sensitive to AVT than is the peripheral vasculature. This may explain in part the antidiuretic action of the hormone at nonpressor doses. Evolutionary speculations are discussed.