Effect of temperature on the anomalous rectification of the membrane of the egg of the starfish, Mediaster aequalis.

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Abstract
The effect of temperature upon the anomalous or inward rectification of the K conductance in the immature egg membrane of the starfish, M. aequalis, was studied using the voltage clamp technique. The K conductance decreases with a relatively small Q10 (1.62) down to about 10.degree. C; below 10.degree. C, the Q10 is much greater (5.8 at [K+]o = 25 mM). The smaller Q10 is independent of [K+]o; the larger one depends on [K+]O. The activation of the rectification depends on V-VK [the membrane potential and the K equilibrium potential, respectively], rather than V alone, at all temperatures at constant internal K concentration. The K conductance at a given V-VK is approximately proportional to the square root of [K+]o at a fixed [K]i above 10.degree. C while the conductance depends substantially less on [K+]o below this temperature. The logarithm of the activation time constant of the inward rectification depends linearly on the membrane potential at all temperatures. The slope of the relation is strongly temperature dependent above about 10.degree. C; the dependence is much less below 10.degree. C: the Q10 of the activation time constant is membrane potential-dependent above 10.degree. C. The mechanism of ion permeation during anomalous rectification probably changes at about 10.degree. C.