Effects of Neurohypophysial Hormones and Their Deamino Analogues on Renal Excretion of Na, K and Water in Rats

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Abstract
Effects of 8-lysine-vasopressin (LVP), oxytocin and their deamino analogues, 1-deamino-8-lysine-vasopressin (deamino-LVP) and 1-deamino-oxytocin, on renal excretion of Na, K and water were studied in anesthetized rats undergoing water diuresis. Replacement of the N-terminal amino group in the LVP and oxytocin molecules by hydrogen had no qualitative effect on the renal activity of the hormones. LVP and deamino-LVP, 0.05 mU (antidiuetic unit)/100 g, produced a prompt inhibition on water diuresis and a mild natriuresis and kaliuresis. Oxytocin and 1-deamino-oxytocin produced a diphasic antidiuretic-diuretic effect and a marked natriuresis and kaliuresis. Antidiuretic responses to the vasopressins were much longer than those to the oxytocins. The structure-activity relationships of these neurohypophysial peptides are discussed. The results suggest that deamino-LVP may be suitable substitute for LVP in the treatment of diabetes insipidus.