Renal function in the hibernating ground squirrel Spermophilus columbianus.

MOY, hZHARD h/I. Renal junction in the hibernating ground squirrel Spermophilus columbianus. Am. J. Physiol. 220(3) : 747-753. 1971. -A tissue-slice analysis showed no solute gradient of urea and sodium from the corticomedullary boundary through the papilla of torpid Columbian ground squirrels. Ground squirrels arousing normally from torpor and sacrificed 15 or 40 min after urine began to flow into a catheterized ureter had distinct renal solute gradients of urea and sodium, whereas arousing squirrels sacrificed before onset of urine flow possessed no such renal gradient. Active homeothermic squirrels, dehydrated 9-l 3 hr, were induced to evacuate the urinary bladder 30 min prior to sacrifice to obtain urine samples. The papillary tissue fluid to urine (TF/U bladder) ratio of urea of these dehydrated homeotherms was consistently less than unity, whereas a similar ratio (TF/U catheter) of arousing urine formers was consistently greater than unity suggesting that squirrels can reabsorb and regulate urea more efficiently during arousal than when dehydrated. No renal potassium gradient existed at any ttime in the ground squirrel. The urea, sodium, and potassium concentrations of plasma did not differ significantly (P > 0.05) at any time.