COLD-RESISTANCE AND OUABAIN-RESISTANCE OF RENAL NA,K-ATPASE IN COLD-EXPOSED AND HIBERNATING JERBOAS (JACULUS-ORIENTALIS)

The temperature dependence and the ouabain sensitivity of Na,K-ATPase was examined in the nephron of normal, cold-exposed, and hibernating j erboas. The transport and hydrolytic activity of renal Na,K-ATPase dis played similar temperature dependence in rats and normal jerboas. Cold -resistance of Na,K-ATPase appeared in cold-exposed jerboas and furthe r increased during hibernation. Three subpopulations of Na,K-ATPase di splaying very high (K-i approximate to 10-(13) M), high (K-i approxima te to 10(-9) M) and low sensitivity to ouabain (K-i approximate to 10( -6) M) were detected in the thick ascending limb and collecting duct o f jerboas. In thick ascending limbs, the subpopulation of very high se nsitivity to ouabain disappeared in cold-exposed animals, which accoun ted for the previously reported decrease in Na,K-ATPase activity. In c ollecting ducts of cold-exposed animals, the subpopulation of very hig h sensitivity to ouabain also disappeared, but the resulting decrease in activity was overbalanced by the appearance of the subpopulation of high sensitivity. (C) 1997 Elsevier Science Inc.