The effect of potassium on the resting metabolism of the frog’s sartorius

Abstract

Solandt, in 1936, found that the rate of heat production of a frog's sartorius at rest is greatly increased by raising the K-ion concentration in the surrounding fluid; Fenn and his colleagues (1930 to 1936) had observed a similar effect with the oxygen consumption. Solandt's findings have been confirmed and extended: (1) the enhanced heat rate is not associated with any mechanical change in the muscle; (2) when a solution with high K (oxygenated) is replaced by oxygen there is usually a large increase in the heat rate, as though something previously being removed by diffusion were accumulating near the surface; (3) with normal Ringer the threshold is at about 10mM-KCl and the full effect at about 18mM, corresponding to membrane potentials of about 65 and 50 mV respectively instead of the usual 90 mV; (4) Ca in about equimolar amounts antagonizes the action of K; (5) Rb acts like K but about twice the concentration is needed; (6) if $\text{NO}_{3}$ or I is substituted for the Cl of Ringer the effect of K is similar but occurs at a lower concentration; (7) if sucrose is substituted for NaCl in Ringer, or $\text{SO}_{4}$ for Cl (provided that the Ca-ion concentration is maintained by saturating with $\text{CaSO}_{4}$), the same effect of K is observed, but with isotonic sucrose alone, or without extra Ca in the $\text{SO}_{4}$-Ringer, a large increase of heat rate occurs without extra K; (8) in the absence of $\text{O}_{2}$ the increment of heat rate due to K is small. It is concluded that a partial depolarization of the surface of the muscle fibres (less than that required to induce contraction) can cause a limited change of internal organization which release some, but not all, of the chemical processes that are normally set in train in a coherent way by excitation. The limited reactions caused by high external K serve no useful physiological function; they are inco-ordinate parts of the normal cycles which are turned on after ordinary contraction has been started by a greater temporary depolarization. The manner in which these internal activities can be induced by a reduction of the potential difference across the surface membrane is discussed.