Atriopeptins and renal cortical and papillary blood flow

Studies were made of the effect of two pure synthetic atrial natriuretic factors (ANF) on renal cortical and papillary blood flow and on the excretion of sodium, potassium and water in young Munich Wistar rats by means of laser-Doppler flowmetry. The effects of Atriopeptin I (AP I), which selectively relaxes intestinal smooth muscle, were compared with those of Atriopeptin II (AP II), which relaxes both vascular and intestinal smooth muscle. Both peptides were administered by continuous intravenous infusion at 10 micrograms h-1 kg-1 body wt after a control period. A time control group was studied in parallel to see whether the variables investigated varied with time. In rats receiving vehicle alone (time control) and in those receiving AP I, there was no significant change either in the cortical or papillary blood flow, or in blood pressure (BP). The AP II infusion resulted in an increase in blood flow which was only transient despite the continuous infusion. Cortical blood flow increased by 22% (peak value) and papillary blood flow increased by 95% (peak value). The blood pressure (BP) decreased by 12% to a steady state level (103 +/- 2 vs. 91 +/- 2 mm Hg). The AP I caused a steady two-fold increase in sodium excretion (UNaV), a 35% increase in potassium excretion (UKV) and and 85% transient increase in urine flow rate (V). Infusion of AP II resulted in a more than 60-fold increase in UNaV during the period of increased blood flow, and then reached a steady state level 10 times higher than the control value.(ABSTRACT TRUNCATED AT 250 WORDS)