Antidiuretic hormone and the distribution of renal cortical blood flow

The radioactive microsphere method was used to study the distribution of cortical blood flow in anesthetized dogs during water diuresis and during antidiuresis. Infusion of antidiuretic hormone (ADH) at rates ranging from 0.33 to 0.5 mU/kg-min into dogs previously volume expanded with 3% dextrose resulted in an increase in urinary osmolality and a significant increase in fractional flow in the inner cortex. Mean arterial pressure, glomerular filtration rate, and renal plasma flow were unaltered by the infusion of ADH at these doses, suggesting that absolute, as well as fractional, blood flow to the inner cortex increased in response to ADH. In three additional experiments, termination of an infusion of ADH in hydropenic dogs and subsequent induction of water diuresis was accompanied by a shift in fractional cortical blood flow away from the inner cortex. The redistribution of cortical blood flow in response to ADH at a time when the kidney is producing a more concentrated urine supports the hypothesis that this vascular effect of ADH may have functional significance in the urinary concentration ability of the kidney.