Abstract

The technic of "stop-flow-" for the localization of renal tubular function has been adapted for use in the rat. The patterns of concentration of sodium, potassium, p-aminohippuric acid, and inulin in this species differ from those reported for the dog only in a quantitative fashion.

Whereas occlusive periods of longer duration (6 minutes) produce clear-cut patterns of concentration for PAH and inulin and define the reabsorptive areas for sodium and potassium, shorter periods of occlusion are essential for the visualization of distal tubular secretion of potassium. Maximal concentrations of the latter were observed following approximately 1 minute of occlusion.

A diminished proximal tubular reabsorption of sodium occurred within 4 days following adrenalectomy and persisted without significant alteration for 40 days postoperatively. A second change, a decrease in the capacity of the distal tubular mechanism to reabsorb sodium, appeared later (21 days after adrenalectomy), and was maximal 28 days postoperatively. Shortly after adrenalectomy (4 days) data were obtained to suggest an increased reabsorptive capacity of the proximal tubules for potassium. No further alteration of potassium concentration in the "stop-flow" pattern occurred at a later time following operation. Administration of desoxycorticosterone restored the "stop-flow" concentrations of both sodium and potassium to levels not significantly different from those of unoperated or sham-operated rats.