Differences in the effect of furosemide and chlorothiazide on the distribution of renal cortical blood flow in the dog.

Abstract

The radioactive microsphere method was used to measure the distribution of renal cortical blood flow before and during the administration of either furosemide or chlorothiazide. In 12 furosemide studies, the per cent flow in outer cortical zone 1 decreased from 42.0 to 35.3 per cent (P <O.OOl), increased from 31.6 to 37.2 per cent (P <O.OOl) and from 17.6 to 20.8 per cent (P <0.025) in midcortical zones 2 and 3, respectively, and decreased from 8.8 to 6.7 per cent (P <O.OOS) in inner cortical zone 4. Total renal blood flow increased in each of 9 studies with a mean increase from 159 to 206 ml. per minute. Zonal blood flow was unchanged during furosemide administration in zones 1 and 4 with essentially the entire increase in cortical blood flow occurring in midcortical zones 2 and 3. In contrast, chlorothiazide decreased total blood flow 14 per cent and had no effect on the distribution of cortical blood flow. Taken together with previous experimental studies, it is suggested that the differences in action of these 2 diuretics on the intrarenal distribution of blood flow is related to their divergent effects on renal vascular resistance. In addition, when the data of various experimental models were evaluated, there was no evidence that a given alteration in the intrarenal distribution of blood flow could be correlated with a consistent change in sodium excretion.