Renal responses of the bullfrog to oxytocin, arginine vasotocin and frog neurohypophysial extract

¹ Department of Pharmacology, Columbia University College of Physicians and Surgeons, New York City

The antidiuretic responses of bullfrogs to oxytocin, frog neurohypophysial extract and arginine vasotocin are compared. Frog extract and arginine vasotocin injected into the ventral lymph sac are approximately 500 times as potent in inhibiting diuresis in frogs as is oxytocin, if they are compared on the basis of oxytocic units. This observation is consistent with the hypothesis that arginine vasotocin is present in the frog neurohypophysis and accounts for its antidiuretic activity in the frog. Diuresis rather than antidiuresis is occasionally seen in bullfrogs after intravenous injection of these preparations. Diuresis is accompanied by an increase in glomerular filtration rate. The presence of diuresis cannot be correlated directly with changes in arterial blood pressure. The mechanism underlying this diuresis remains obscure.