Ouabain-insensitive K influx in Hydrodictyon africanum

Summary The occurrence is reported of cells of Hydrodictyon africanum which have, contrary to previous reports by the author, a K influx which is almost insensitive to ouabain. The conditions which govern the ouabain-sensitivity of the K influx have not yet been defined. The low ouabain sensitivity of the total K influx seems to be related to a smaller than usual activity of the component of K influx which is linked to Na efflux, and also to a smaller sensitivity of this component to inhibition by ouabain. The major components of K influx in ouabain-insensitive cells correspond to those components previously described as the passive and Cl-linked components.The occurrence is also reported of an increased sensitivity of active Cl influx (and the coupled cation influxes) in the light to uncouplers when the medium is aerated or otherwise stirred.