Effect of hypothermia on tubular transport mechanisms.

Abstract

Five mongrel dogs were cooled artificially to 20°C and then rewarmed to 37°C, while changes in the concentration of glucose, phosphorus, amino acid nitrogen, protein and creatinine in both plasma and urine as well as changes in urine flow were studied periodically. A decrease in serum amino acid nitrogen concentration occurred with cooling. The reverse was seen upon rewarming. Serum creatinine and protein levels were essentially unchanged. Urine flow increased with cooling and the U/P ratios of phosphorus, amino acid nitrogen and creatinine decreased. There was minimal increase in protein excretion while all of the filtered glucose appeared in the urine. The changes in urinary composition indicate that two transport mechanisms are involved in the reabsorption of amino acids and phosphorus from glomerular filtrate. Only one of these is affected by cooling. The mechanism responsible for glucose reabsorption is paralyzed by cold, while the effect of cold on protein reabsorption could not be quantitated by these studies.