Energetics of sodium transport in frog skin. I. Oxygen consumption in the short-circuited state

Abstract

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/dO(2) 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/dO(2) 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.