Inhibition of renal tubular function by cold.

Abstract

In an attempt to inhibit the renal tubular production of NH3 and CO2, alligators were exposed for long periods of time to temperatures as low as 5°C. Cold increased the concentration of the urinary Na, Cl, Ca, Mg and glucose while it decreased the excretion of NH3, CO2 and phosphate. When the effect was maximal the composition of the urine closely resembled that of the plasma except for a decreased protein and somewhat elevated CO2 content. The fact that the injection of Diamox into cold alligators was necessary to reduce the CO2 to the plasma level would seem to indicate that carbonic anhydrase was not totally inhibited by cold. Although cold reduced the clearances of both thiosulfate and creatinine, their U/P ratios of about 6/1 were not affected by temperature changes. Since PO4 is normally excreted by the tubules of the alligator, this ion was injected to test the effect of cold on tubular excretion. With the decrease in temperature the PO4 U/P ratio fell from 30/1 to 5/1. It was concluded that cold almost eliminates renal tubular activity in the alligator. Several experiments were also performed on turtles with similar results.