Effects of atrial natriuretic peptide on regional renal blood flow measured by a thermal diffusion technique

The effects of atrial natriuretic peptide (ANP) on the regional renal blood flow were examined in anesthetized dogs. A thermal diffusion technique was applied in an attempt to observe the intrarenal blood distribution. Tissue blood flow was continuously measured according to the changes of the thermal gradient produced by a semiconductor (Peltier effect). The data (x) obtained by these probes were closely related to those (y) of the ion gas clearance method (the probe for cortical blood flow; y = 1.08x-6.23 r = 0.99, the probe for medullary blood flow; y = 1.00x +0.26 r = 0.99). The basal values of cortical and medullary blood flows measured with the flow probe in anesthetized mongrel dogs were 85 +/- 16 and 55 +/- 9 ml/min/100 g kidney weight, respectively. ANP was infused into renal artery at doses of 0.01 (n = 6), 0.05 (n = 8), 0.3 (n = 6) micrograms/kg/min and the effect on renal hemodynamics and renal excretory functions was observed. The effect was also compared with that of furosemide. Low dose of ANP did not affect renal blood distribution. Intermediate dose of ANP selectively increased medullary blood flow from 46 +/- 8 to 62 +/- 7 ml/min/100 g kidney weight, and higher dose significantly increased both cortical and medullary blood flow. ANP produced diuresis and natriuresis in a dose-dependent manner, which was not necessarily related to the changes of intrarenal blood distribution. Furosemide did not affect the renal hemodynamics. Several parameters of renal functions such as lithium and free water clearances, showed changes different from those with ANP infusion.(ABSTRACT TRUNCATED AT 250 WORDS)