Renal function in the hibernating, and hypothermic hamster Mesocricetus auratus.

Plasma and urine concentrations of Na+, K+, and urea were examined in hibernating, hypothermic, and normothermic hamsters. Plasma Na+ and K+ appear unaffected by 48 h of hypothermia (T-re 7 degrees C); however, plasma Na+ increased (P smaller than 0.05) from control values of 125.8 plus or minus 10.2 to 173 plus or minus 9.2 meg/liter in hibernators. Plasma K+ of the hibernator increased to 9.6 plus or minus 3.2 meq/liter from control values of 5.5 plus or minus 0.8 meq/liter (P smaller than 0.05). Plasma urea concentrations were increased (P smaller than 0.05) in both metabolically depressed groups from a control value of 0.5 plus or minus .05 to 0.8 plus or minus .16 and 7.2 plus or minus 2.8 mM in hypothermic and hibernating groups, respectively. Urine concentrations of solute for the hypothermic animals showed no detactable change from control values for Na+ and a decrease for both K+ and urea. Concentrations from hibernators showed a decrease from control values for both Na+ and K+ with no detectable change in urea. Renal tissue slice analysis demonstrated a marked corticomedullary solute gradient for Na+ and urea in normothermic control animals which is eliminated in hamsters hypothermic for 48 h and reduced in animals hypothermic for 15 min. Rewarming animals did not show a return of the solute gradient at T-re 18 degrees C. However, animals that had rewarmed to T-re 37 degrees C demonstrated a complete return with no difference (P greater than 0.05) from control values. Hibernators showed a slight (P smaller than 0.05) gradient for Na+ and no gradient for urea. Animals in all instances demonstrated a decrease in K+ concentration from cortex to papilla. A greater concentration of K+ was found in the renal cortex of animals hypothermic for 15 min and in hibernators (P smaller than 0.05).