Abstract
In conjunction with certain experiments on the mechanism of chloride reabsorption by the tubules of the kidney of the dog in a heart-lung perfusion system as described by Verney and Starling, 1 we have had occasion to observe some interesting relations between renal blood flow, perfusion pressure, chloride concentration and total chloride excreted in the urine.
Winton 2 has pointed out that the rate of blood flow through the kidney is a factor of secondary importance, as compared with the glomerular filtration pressure, in determining the character and quantity of urinary secretion. Numerous observations have indicated to us an indubitable relation, nevertheless, between renal blood flow and urinary secretion, particularly in the case of spontaneous changes in the former.
Figure 1 shows graphically the results of a type of experiment in which concomitant with a rising renal blood flow, from 110 to 210 cc. per minute, while the perfusion pressure was kept substantially constant for 35 minutes, there was an increase in urine flow from 0.35 cc. to 4.8 cc. per minute, and an increase in chlorides from 50 to 150 mg. %. This sort of behavior has been noted in a number of instances after the kidney has begun to secrete well.
These observations are not in any sense contradictory to those of Winton, because he was dealing with changes induced in the rate of blood flow by altering the pressures in the renal vein and the ureter. Moreover, we believe that our observations can be interpreted best by ascribing the results to changes in the state of constriction of certain portions of the vascular bed in the kidneys resulting in changes in glomerular filtration pressure as outlined below.
An increase in the rate of renal blood flow at constant perfusion pressure could result only from a vasodilation in some regions of the vascular bed of the kidney.
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