Activation of an electrogenic sodium pump in the smooth muscle cell membrane of guinea pig taenia coli during recovery after cold treatment.

Abstract

The characteristics of hyperpolarization occurring in the smooth muscle cell membrane of the guinea pig taenia coli during recovery after cold shock (10°C) were investigated using the doublesucrose gap method.1. During the cold shock, the membrane resistance was initially reduced. This was followed by an increase. The membrane was depolarized throughout. The initial reduction of the membrane resistance and hyperpolarization of the membrane during rewarming showed approximately linear relationship.2. The duration of cold shock also showed a linear relationship to the amplitude of the hyperpolarization.3. The reduction of the membrane resistance was thought to be due to an increase of the Na conductance. The subsequent increase of the membrane resistance and depolarization were thought to be mainly due to nonselective suppression of ionic permeability and partly due to reduction of the emf.4. In Na-free and in K-deficient solutions, the initial reduction of the membrane resistance during the cold shock and the hyperpolarization after the recovery were not observed.5. Cl-deficient (C6H5SO3) and Ca-free solutions did not suppress the generation of the hyperpolarization during the recovery process from cold shock.6. Ouabain (10-6g/ml) suppressed the hyperpolarization of the membrane during the recovery process.7. The mechanisms involved in the generation of hyperpolarization during the recovery process after cold shock are discussed. The nature of the hyperpolarization is postulated to be due to activation of an electrogenic Na pump during the recovery after the cold shock.