Temperature compensation of sodium transport and ATPase activity in frog skin

Na⁺ transport across frog skin, measured as short-circuit current (SCC) shows perfect temperature compensation in frogs acclimated to 6°, 12°, and 23°C as SCC values observed at the acclimation temperatures are equal (about 13 μA/cm²). Reacclimation experiments show that this is not a starvation effect. While very little temperature compensation is seen in the activity of Na⁺, K⁺-ATPase in epidermal homogenates from frog skins, the activity of Mg²⁺-ATPase shows inverse compensation at assay temperatures from 4^o to 48^oC. This ATPase is apparently activated either by Mg²⁺ or by Ca²⁺ and it probably controls the passive permeability of epidermal cells. It is suggested that the inverse temperature compensation in the activity of this enzyme is the main mechanism by which the observed perfect temperature compensation of Na⁺ transport across frog skin occurs.