EFFECT OF TEMPERATURE AND OUABAIN ON THE NA+-K+ ACTIVATED MEMBRANE ATPASE AND ELECTROGENIC IONIC PUMP OF THE GOLDEN-HAMSTER AND MOUSE DIAPHRAGM

  • 1 January 1980
    • journal article
    • research article
    • Vol. 29  (6) , 543-552
Abstract
The activity of membrane Na+-K+-ATPase and electrogenic ionic pump was estimated by biochemical and electrophysiological techniques on diaphragm muscles of mouse and non-hibernating golden hamster [Mesocricetus auratus] between 5-37.degree. C. The electrogenic capacity of ionic pump (measured as maximum hyperpolarization after adding 5 mmol/l K+ to Na+-enriched muscle) was highest at 37.degree. C for the mouse and at 25-30.degree. C for the golden hamster. At lower temperatures [5-15.degree. C], the hyperpolarization after adding K+ reversed to depolarization between 10-15.degree. C and in the mouse. In the hamster, the slight hyperpolarization persisted even at 5.degree. C. With decreasing temperature the activity of membrane ATPase of mouse and hamster membrane fraction decreased to the same extent between 25-37.degree. C. Within the temperature range between 5-10.degree. C enzyme activity in hamster preparations was .apprx. 2.4 times higher than in the mouse. In the mouse Na+-enriched diaphragm, ouabain [10-4 mol/l] decreased the resting membrane potential [RMP] in a K+-free solution at 20.degree. C by about 5 mV. In the golden hamster preparation, ouabain in the same concentration increased RMP of Na+-enriched diaphragm fibers by more than 5 mV. The activity of membrane ATPase of hamsters was increased by 10-4 mol/l ouabain more than 2.5 times in a K+-free reaction medium. In the mouse no change of enzyme activity was observed. Ouabain apparently can be substituted for K as an activator of membrane ATPase in the sarcolemma of golden hamster muscle fibers.