Energetics of Sodium Transport in Frog Skin : I. Oxygen consumption in the short-circuited state

Sodium transport and oxygen consumption were studied simultaneously in the short-circuited frog skin. Sodium transport was evaluated from I_o/F, where I_o is the short-circuit current measured with standard Ringer's solution bathing each surface and F is the Faraday constant. Oxygen tension was measured polarographically. Under a variety of circumstances the rate of oxygen consumption from the outer solution exceeded that from the inner solution, the ratio being constant (0.57 ± 0.09 SD). Both I_o and the associated rate of oxygen consumption J_ro declined nonlinearly with time, but the relationship between them was linear, suggesting that the basal oxygen consumption was constant. For each skin numerous experimental points were fitted by the best straight line. The intercept (J_ro)_Io=0 then gave the basal oxygen consumption, and the slope dNa/dO₂ gave an apparent stoichiometric ratio for a given skin. The basal oxygen consumption was about one-half the total oxygen consumption in a representative untreated short-circuited skin. Values of dNa/dO₂ in 10 skins varied significantly, ranging from 7.1 to 30.9 (as compared with Zerahn's and Leaf and Renshaw's values of about 18). KCN abolished both I_o and J_ro. 2,4-dinitrophenol (DNP) depressed I_o while increasing J_ro four- to fivefold. Anti-diuretic hormone stimulated and ouabain depressed both I_o and J_ro; in both cases apparent stoichiometric ratios were preserved.