Abstract

To assess the effect of furosemide on renal blood flow, the drug was administered to mongrel dogs in which initial renal vascular resistance was varied by different conditions of i.v. loading. Two levels of saline as well as mannitol load were the i.v. loading conditions used. Changes in renal blood flow were measured with an electromagnetic flowmeter. The results indicated that furosemide decreases renal vascular resistance and thereby increases renal blood flow in saline-loaded animals but does not alter renal vascular resistance and therefore has no effect on renal blood flow in mannitol-loaded animals. It appears that the capacity of furosemide to elevate renal blood flow could be related to the initial resistance of certain vascular segments within the kidney. The higher the initial resistance in such segments, the greater the effect of this agent on renal blood flow. Total renal resistance does not always predict whether or not furosemide will increase blood flow inasmuch as total resistance can be very low, yet areas within the renal vascular bed that are responsive to the agent could still have a higher resistance and thus be responsive to the drug.