Effects of [Ca2+]i and temperature on minK channels expressed in Xenopus oocytes.
Slowly activating, voltage-dependent minK channels cloned from rat kidney were expressed in Xenopus oocytes. Increase in the bath temperature from 22 to 32 degrees C resulted in a dramatic acceleration of minK channel activation. The extraordinarily high Q10 of minK channel activation was voltage-dependent, being higher at more negative potentials (Q10 at -20 mV; 7.02; at 20 mV: 4.0). While activation of minK channels was highly voltage-dependent at 22 degrees C, voltage had only little effect on minK channel activation at 32 degrees C. Increase in [Ca2+]i which has recently been shown to increase the maximal conductance gmax at room temperature, did not affect gmax at 32 degrees C. However, increase of [Ca2+]i caused acceleration of minK channel activation at both temperatures. The interaction of [Ca2+]i and temperature on gmax and activation rate of minK channels described here is very similar to recent findings on Ca- and temperature-effects on the slowly activating potassium conductance IKs in guinea pig cardiac myocytes.
Busch
A E
AE
Physiologisches Institut I, Eberhard-Karl-Universität Tübingen, Germany.
Lang
F
F
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D004553:Electric Conductivity; D005260:Female; D006168:Guinea Pigs; D006321:Heart / Q000502:physiology; D066298:In Vitro Techniques; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D015221:Potassium Channels / Q000096:biosynthesis / Q000187:drug effects / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D013696:Temperature; D014981:Xenopus
D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; C059983:potassium channel protein I(sk); D000001:Calcimycin; D002118:Calcium