The temperature dependence (TD) of the membrane repolarization process (RP) in muscle cells within the range of 10--20 degrees C following preliminary cooling of muscles, the effect of treatment of diaphragmatic muscles (DM) with ouabain (Ou) (10(-4) M) and administration of 2,4-dinitrophenol (2,4-DNP) (1.5 mg/100g) on RP were studied in experiments on isolated DM of adult (7--8-month-old) and old (28--32-month-old) male white rats. Ou and 2,4-DNP decrease the temperature coefficient Q10 of cell membrane RP of DM in the adult animals to the magnitudes approximating one, while in the old animals, 2,4-DNP does not change TD of RP and Ou reduces it from 3.824 +/- 0.440 but to 2.725 +/- 0.245. A possible age-associated reconstitution of the mechanisms of active transmembrane ion transport is suggested.