Fluxes of Sodium and Potassium in<i>Acetabularia mediterranea</i>

Abstract

Sodium efflux in Acetabularia mediterranea occurs against a gradient of electrochemical potential and is a light-stimulated, temperature-sensitive process; it is not sensitive to the uncoupler CCCP. Sodium influx is stimulated in CCCP and at low temperature. Potassium influx is temperature- and uncoupler-sensitive, but is not light-stimulated. Tracer K efflux shows complex kinetics, which cannot be explained by any arrangement of intracellular compartments; it appears to be stimulated at low temperature and is insensitive to light and uncouplers. There is no evidence for any chemical linkage between fluxes of Na+, K+, or Cl–. It is concluded that Na– efflux at the plasmalemma is an active process, but no consistent explanation can be advanced to account for the results of K+ flux measurements.