Effects of centrally administered atrial natriuretic peptide on renal functions.

In order to assess the effects of centrally administered atrial natriuretic peptide (ANP) on renal water and electrolytes handling, arterial blood pressure, plasma vasopressin, renin activity, aldosterone, and ANP concentrations, synthetic alpha-human ANP (alpha-hANP) was administered intracerebroventricularly at a dose of 2.6 pmol.kg-1.min-1 for 30 min in pentobarbital-anaesthetized dogs (N = 6). In the control study (N = 6), artificial cerebrospinal fluid was infused. Intracerebroventricular administration of alpha-hANP increased significantly urine flow from 178 +/- 37 to 303 +/- 43 microliter/min (mean +/- SEM), sodium excretion from 27.3 +/- 8.9 to 54.4 +/- 10.5, mumol/min, potassium excretion from 16.1 +/- 3.7 to 24.0 +/- 5.1 mumol/min, and osmolar and negative free water clearances, accompanied by a significant rise in renal blood flow from 77.0 +/- 14.6 to 94.9 +/- 16.9 ml/min. Whereas glomerular filtration rate fell significantly, blood pressure and heart rate did not change. Plasma ANP, aldosterone, and PRA did not change significantly during the experiment, but plasma AVP were slightly but significantly decreased from 52 +/- 11 to 34 +/- 6 nmol/l. On the other hand, these parameters showed no changes in the control study, except a significant fall in glomerular filtration rate and a significant rise in PRA. Thus, it has been confirmed that ANP centrally brings about diuresis, natriuresis, and kaliuresis via some unknown mechanisms independent of the release of these hormones.