Glutaraldehyde inhibits the active transport of sodium and the oxygen consumption, while increasing the water diffusional permeability in frog skin

A detailed investigation of the effects of mild glutaraldehyde (GA) treatments on both active and passive transport properties of isolated frog skin is presented. The active transport of sodium, as expressed by the short-circuit current, is gradually inhibited when GA is present in the Ringer solution on the serosal face of the skin, even at 0.01% (w/v) concentration. The inhibition is roughly exponential, with time constants ranging from 19 min (at 25 degrees C and 0.10% aldehyde), up to 63 min (at 10 degrees C and 0.01% aldehyde). It seems be partly due to (or, at least, is concomitant with) the inhibition by GA of the tissular oxygen consumption. This is reduced to half of the initial value by 0.10% GA. Higher GA concentrations (0.10 to 1.0%) increase with up to 50% the transepithelial diffusional permeability of water, and also produce even more pronounced increments in the diffusional permeabilities for sodium and potassium. All these data are consistent with the image of GA cross-linking between the free amino (and other reactive) groups on the proteins. This probably results in the severe modification of every functional protein aggregate, thus inactivating the transport ATPases, but also causes a stabilization of protein hydrophilic membrane domains making the water and the small ions to penetrate easier. In view of these opposite effects on active and passive transport of ions, the possibility of using GA at concentrations around 0.05% (w/v) to block the active transport through frog skin and other tight epithelia is suggested.