The Potassium Content of Gonyaulax polyedra and Phase Changes in the Circadian Rhythm of Stimulated Bioluminescence by Short Exposures to Ethanol and Valinomycin 1

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RESUMO

A circadian rhythm in the intracellular level of K+ in Gonyaulax polyedra is reported. When axenic cultures of Gonyaulax in continuous light (60-75 fot candles) are exposed for 4 hours to 0.1 or 0.2% ethanol, the subsequent free-running rhythm in stimulated bioluminescence is phase-shifted, the amount and direction of the shift being dependent on the time in the circadian cycle when cells are treated. The phase-response curve for ethanol closely resembles that for light in similarly maintained cells. When valinomycin (0.1 or 0.2 μg ml−1) is present in addition to ethanol, the phase of the bioluminescence rhythm is returned to that of an untreated cell suspension. Valinomycin thus negates the effect of ethanol on phase. The intracellular K+ level immediately after treatment of a cell suspension for 4 hours with ethanol (0.1%) is about half that of untreated cells. If valinomycin (0.1 μg ml−1) is also present during the 4-hour treatment, the intracellular K+ is only slightly lower than in untreated cells. Increasing the external concentration of K+ or Na+ for 4 hours has no effect on the rhythm of stimulated bioluminescence. These results are interpreted as support for the hypothesis that the mechanism by which circadian oscillations are generated involves changes in membrane properties.

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