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Abstract

The currents through single Ca²⁺-activated K⁺ channels were studied in excised inside-out membrane patches of human erythrocytes. The effects of temperature on single-channel conductance, on channel gating and on activation by Ca²⁺ were investigated in the temperature range from up 0 to 47° C. The single-channel conductance shows a continuous increase with increasing temperature; an Arrhenius plot of the conductance gives the activation energy of 29.6 ± 0.4 kJ/mol. Reducing the temperature alters channel-gating kinetics which results in a significant increase of the probability of the channel being open (P_o). The calcium dependence of P_o is affected by temperature in different ways; the threshold concentration for activation by Ca²⁺ is not changed, the Ca²⁺ concentration of half-maximal channel activation is reduced from 2.1 μmol/l at 20° C to 0.3 μmol/l at 0° C, the saturation level of the dependence is reduced for temperatures higher then about 30° C. The relevance of the obtained data for the interpretation of the results known from flux experiments on cells in suspensions is discussed.