The effect of antidiuretic hormone on intrarenal microsphere distribution

The aim of the present study was to reexamine the effect of antidiuretic hormone on intrarenal blood flow distribution by the microsphere technique in anaesthetized rats. The administration of 3, 6 or 60 mU/kg/h of arginine-vasopressin (VP) was accompanied by a dose-dependent antidiuresis. Glomerular filtration rate increased only at the dose level of 60 mU/kg/h and was not significantly altered by the lower doses. Total renal blood flow was not significantly influenced by any of the doses of VP. The two small doses caused no change in intracortical microsphere distribution but there was a significant decrease in the ratio of outer to inner cortical blood flow when 60 mU/kg/h of VP was infused. The results indicate that physiological doses of VP do not alter the distribution of intrarenal blood flow and show that the antidiuretic effect of VP is independent of changes in renal haemodynamics.