Accelerated Natriuresis Induced by Synthetic Atrial Natriuretic Polypeptide in Spontaneously Hypertensive Rats

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Abstract
Effects of synthetic .alpha. human atrial natriuretic polypeptide (.alpha.-hANP) on diuresis, natriuresis and mean arterial blood pressure (MAP) were compared between 4-5 m.-old male spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) under ether anesthesia. In both groups, the peptide injected (0.5 .mu.g/100g body wt, i.v.) caused potent (about 10-fold), rapid and short-acting (for 15 min) increased in Na and chloride excretions and an increase in urine flow and K extrection with lesser magnitude. Although ratios of the maximum response to basal value were much the same, net increases in urine flow and Na+ output were significantly greater in SHR than in WKY. As to the effect on MAP, a rapid (within 2 min) fall of 9.5% on the average from control levels was equally observed in the 2 groups. The atrial natriuretic peptide may evidently be involved in the altered regulatory mechanism of fluid and electrolyte balance in SHR models with genetic hypertension.