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

1. The effect of temperature upon the anomalous or inward rectification of the K conductance in the immature egg membrane of the starfish, Mediaster aequalis, was studied by using voltage clamp technique. 2. The K conductance decrease with a relatively small Q10 (1.62) down to about 10 degrees C; below 10 degrees C, the Q10 is much greater (5.8 at [K+]o = 25 mM). The smaller Q10 is independent of [K+]o, whereas the larger one depends on [K+]o. 3. The activation of the rectification depends on V-VK, rather than V alone, at all temperatures at constant internal K concentration. 4. 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 degrees C while the conductance depends substantially less on [K+]o below this temperature. 5. The logarithm of the activation time constant of the inward rectification depends linearly on the membrane potential at all temperatures. 6. The slope of the relation is strongly temperature dependent above about 10 degrees C whilst the dependence is much less below 10 degrees C; i.e. the Q10 of the activation time constant is membrane potential-dependent above 10 degrees C. 7. The results suggest that the mechanism of ion permeation during anomalous rectification changes at about 10 degrees C.