Saluretic actions of neurohypophysial peptides in conscious dogs

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

The effects of arginine vasopressin, oxytocin and two synthetic analogues, arginine vasotocin (8-arginine oxytocin) and oxypressin (8-leucine vasopressin), on urinary electrolyte excretion were studied in conscious dogs. Arginine vasopressin, 0.25 mu/kg, evokes a consistent natriuretic response during water diuresis, while at low urine flows the natriuretic response is usually absent. Oxytocin, 6–7 mu/kg, produces consistent natriuresis only at low urine flows. In higher doses, however, both hormones produce natriuresis either during water diuresis or at low urine flows. When doses of equal antidiuretic activity are injected arginine vasotocin produces greater natriuresis than arginine vasopressin; in this respect, oxypressin is the least potent. The kaliuretic effects of these four peptides are inconsistent. These studies suggest that the 8-arginine of vasopressin is important to natriuretic activity. Substitution of isoleucine for 3-phenylalanine in the ring also increases natriuretic activity relative to antidiuretic activity. This implies that the oxytocin ring also contributes to the saluretic activity of neurohypophysial peptides.

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