EFFECTS OF TEMPERATURE AND METABOLIC INHIBITORS ON THE ACTIVE Na TRANSPORT IN FROG SKIN

Abstract

By using a servo-mechanical system the potential difference between the inner and the outer surfaces of a frog skin was clamped at zero mV and the short-circuit current was measured. The following results were obtained: The short-circuit current is thermo-reversible between about 3[degree]C and 22[degree]C. This is also proved when an inhibitor is applied to the frog skin. Between 6[degree]C and 20[degree]C the short-circuit current is almost equal to the net sodium transport at each temperature. This is proved by using the double labelling method. Based upon the thermodynamics of irreversible process the short-circuit current is deduced to be the change of Gibbs free energy. The short-circuit current is so influenced by the temperature that the curve log Is/Is20-1/T consists of two parts: the one for the normal and the other for low temperature. The point of intersection lies between 10[degree]C and 15[degree]C. The temperature coefficient of the short-circuit current at low temperature is larger than that in the normal temperature region. Some inhibitors decrease the short-circuit current in the normal as well as in the low temperature regions. They do not markedly affect the temperature coefficient in the normal temperature region, but in the low temperature region they have a marked effect on the temperature coefficient. The electrical conductance was measured. The curve C-t also consists of two parts: the normal and the low temperature regions. The boundary usually lies between 10[degree]C and 15%. At least two or more mechanisms, including enzymatic action, are concerned with the Na-active transport in the frog skin.