The human red cell voltage-regulated cation channel. The interplay with the chloride conductance, the Ca(2+)-activated K(+) channel and the Ca(2+) pump.
The activation/deactivation kinetics of the human erythrocyte voltage-dependent cation channel was characterized at the single-channel level using inside-out patches. It was found that the time dependence for voltage activation after steps to positive membrane potentials was slow ( t(1/2) about 30 s), whereas the deactivation was fast ( t(1/2) about 15 ms). Both activation and deactivation of this channel were also demonstrated in intact red cells in suspension. At very positive membrane potentials generated by suspension in extracellular low Cl(-) concentrations, the cation conductance switched on with a time constant of about 2 min. Deactivation of the cation channel was clearly demonstrated during transient activation of the Gárdos channel elicited by Ca(2+) influx via the cation channel and ensuing efflux via the Ca(2+) pump. Thus, the voltage-dependent cation channel, the Gárdos channel and the Ca(2+) pump constitute a coupled feedback-regulated system that may become operative under physiological conditions.
D000222:Adaptation, Physiological / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000502:physiology*; D002478:Cells, Cultured; D018118:Chloride Channels / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D004910:Erythrocyte Membrane / Q000502:physiology*; D004912:Erythrocytes / Q000502:physiology; D005246:Feedback / Q000502:physiology; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology; D006801:Humans; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D007473:Ion Channels / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology*; D017711:Nonlinear Dynamics; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D024681:Potassium Channels, Calcium-Activated / Q000187:drug effects / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated / Q000187:drug effects / Q000502:physiology*
D018118:Chloride Channels; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; D007473:Ion Channels; C496923:KCNN4 protein, human; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D024642:Potassium Channels, Voltage-Gated; D000252:Calcium-Transporting ATPases; D011188:Potassium; D002118:Calcium