Effect of reduction in filtration rate on renal tubular sodium and water reabsorption

Publisher Website
Google Scholar
Abstract
The effect of an acute reduction in glomerular filtration rate (GFR) on renal tubular Na and water reabsorption in the rat was studied by a micropuncture technique involving repeated collections from the same tubular segments during normal and reduced GFR. When GFR was reduced by means of a clamp on the renal artery, proximal tubular passage time was prolonged and fractional reabsorption of Na and water was increased. Although GFR was reduced by a mean of 50%, proximal fractional reabsorption was increased by a mean of only 14%, indicating partial matching of reabsorption to filtration. An adjustment of Na reabsorption to tubular flow rate also occurred in the loop of Henle since the fraction of the loop sodium load reabsorbed remained relatively unchanged during reduced GFR. However, a progressively smaller fraction of the water entering the loop was reabsorbed when flow rate was enhanced leading to an increased Na concentration of the tubular reab-sorbate. On the other hand, the Na concentration of early distal tubular fluid was increased during reduced GFR even though urinary Na concentration and excretion rate fell to low levels. Reduction in delivery of Na and water to the distal tubule and collecting duct resulted in more complete fractional reabsorption, a behavior consistent with a fairly fixed absolute reabsorptive rate in these segments.

This publication has 17 references indexed in Scilit: