Effects of Saline Loading on Distal Renal Tubular Sodium and Water Reabsorption. ∗

Summary

The stop flow method was used to determine the effects of saline loading on distal renal tubular function in hydropenic dogs. Stop flow experiments were performed in 6 dogs early and late in the course of an increasing diuresis induced by saline loading. Distal tubular stop flow patterns were compared with regard to the sodium clearance ratio (U/P Na/U/P creatinine) and U/P creatinine values. Stop flow patterns obtained late in the diuresis consistently showed elevations of all distal sodium clearance ratios, including the minimum, and decreases in all U/P creatinine values. These data suggest that an inhibition of sodium and water reabsorption develops in the distal tubule during saline loading. This could be characterized only as a fractional rather than an absolute decrease in distal reabsorption. It appeared that the inhibition was not a flow rate dependent phenomenon. Reabsorption at other tubular sites was not evaluated because of limitations inherent in stop flow methodology.