The effects of intravenous injection of alpha-human atrial natriuretic polypeptide on blood pressure, renal hemodynamics and urinary kinin excretion in anesthetized rabbits.

Studies were performed in anesthetized rabbits to examine the effects of alpha-human atrial natriuretic polypeptide (alpha-hANP) on blood pressure, renal hemodynamics and urinary kinin excretion. Intravenous bolus injection of alpha-hANP at a dose of 5 micrograms resulted in a transient increase in renal blood flow from 26.6 +/- 2.2 to 33.7 +/- 2.2 ml/min (p less than 0.05) and a decrease in mean arterial pressure from 113 +/- 1.8 to 107 +/- 2.2 mmHg (p less than 0.01). The calculated renal vascular resistance decreased from 4.50 +/- 0.34 to 3.28 +/- 0.20 mmHg/ml/min (p less than 0.05). This vasodilatory effect of alpha-hANP was immediate and lasted for 30 min. These hemodynamic alterations were not associated with the changes in glomerular filtration rate estimated by creatinine clearance. Intravenous injection of alpha-hANP also produced marked increases in urine volume from 1.99 +/- 0.43 to 5.7 +/- 1.20 ml/10 min (p less than 0.01), urinary sodium from 42.2 +/- 7.6 to 243 +/- 54 mu Eq/10 min (p less than 0.01), urinary potassium from 37.5 +/- 5.5 to 74.8 +/- 10.3 mu Eq/10 min (p less than 0.01), and urinary kinin excretion from 3.44 +/- 0.49 to 5.26 +/- 0.82 ng/10 min (p less than 0.05). The observed natriuretic effect of alpha-hANP lasted only for 30 min, whereas diuretic and kaliuretic effects were sustained for 120 min. Hematocrit levels did not change significantly throughout the experiment. These results indicate that alpha-hANP is a potent vasodilator substance and that the natriuretic effect induced by the bolus injection of alpha-hANP is mediated mainly through its renal vasodilatory action. It is also suggested that the renal kinin, at least in part, contributes to the natriuretic effect of alpha-hANP.