Electrical currents through full-grown and maturing Xenopus oocytes.

An extracellular vibrating electrode was used to map the current pattern around Xenopus laevis oocytes. Current was found to enter the animal hemisphere and leave the vegetal hemisphere; in fully grown oocytes from which the follicle cells had been removed, the maximal current density was about 1 microamperemeter/cm2. This current decreased to nearly zero in response to progesterone and several other maturation-producing agents. In the case of progesterone, the decline began within a few minutes of the addition of the hormone and proceeded with a half-time of about 20 min. An analysis of the effects on the current of the removal or addition of various ions and drugs led to the inference that the major current-carrying ion was chloride and that the chloride permeability was controlled by calcium.