Summary
Inactivation of the K inward current through the anomalous rectifier channel of the egg cell membrane of a tunicate,Halocynthia roretzi Drashe, was studied under voltage-clamp. The noise spectrum of the steady-state current recorded at hyperpolarized potentials was measured in solutions in which Na, Cs, Hydrazine, or Sr caused inactivation of the current. The unitary conductance estimated was independent of which cation caused inactivation. From the relation between the concentration of cations which caused inactivation and the extent of inactivation at fixed potentials, the binding of one inactivator to a channel was found to cause inactivation, and the potency of inactivation was Cs+>Hydrazine+>Na+>Li+, and Ba2+>Sr2+. The inactivation caused by Na+ was increased by K+ when [K] o was lower than 20mm, but was decreased by K+ in higher K-ASW (artificial sea water). One K+ was found to inactivate the channel cooperatively with one Na+. Increase of inactivation by K+ was a dominant effect in Cs-ASW. The inactivation was explained quantitatively by a model assuming cooperative plugging by a monovalent inactivator and a K+.
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Ohmori, H. Dual effects of K ions upon the inactivation of the anomalous rectifier of the tunicate egg cell membrane. J. Membrain Biol. 53, 143–156 (1980). https://doi.org/10.1007/BF01870582
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DOI: https://doi.org/10.1007/BF01870582