Effect of antidiuretic hormone and indomethacin on intrarenal microsphere distribution.

The purpose of the present study was to reexamine the effect of antidiuretic hormone (ADH) and indomethacin (IM) on intrarenal blood flow distribution by applying the microsphere technique to trained consciuous dogs. ADH and IM were given separately and jointly during maximal water diuresis. ADH in itself caused moderate antidiuresis and marked natriuresis. Although IM by itself had no significant effect on urinary osmotic concentration or solute excretion it greatly enhanced the antidiuretic effect of ADH and abolished its natriuretic effect. Intrarenal blood flow distribution remained unchanged when ADH and IM were given separately but it was shifted toward the inner cortex when the drugs were administered simultaneously. Furthermore, transition from spontaneous antidiuresis to maximal water diuresis did not alter intrarenal blood flow distribution. The results indicate that ADH induced antidiuresis is dissociated from changes in intracortical blood flow distribution. However, the possibility that IM enhancement of ADH mediated antidiuresis is at least in part mediated by intrarenal hemodynamic changes cannot be excluded.