Ca(2+)-conductances in cultured rat retinal pigment epithelial cells.
Membrane conductances for Ca2+ in cultured rat pigment epithelial cells were studied in the whole-cell configuration of the patch-clamp technique using barium (10 mM) as a charge carrier. Two types of voltage-dependent and verapamil- and diltiazem-sensitive Ba2+ currents were observed. First, a nearly sustained current was activated by depolarization to potentials more positive than -30 mV and blocked by nifedipine (1 microM). This current was observed in cells of primary cultures less than 13 days old. Second, a transient nifedipine (1 microM) insensitive current was activated by depolarization to potentials more positive than -55mV in cultures which were more than 13 days old. This current was not carried by sodium and blocked by 1 microM tetrodotoxin (TTX). In summary, cultured rat retinal pigment epithelial cells in younger primary cultures express Ba2+ currents indicating the presence of L-type Ca2+ channels. In older primary cultures a low-voltage activated channel was observed with properties different from T-type calcium channels or TTX-sensitive calcium conducting sodium channels.
Department of Neurobiology, Battelle Institute, Frankfurt am Main, Germany.
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D000375:Aging / Q000378:metabolism / Q000502:physiology; D000818:Animals; D015220:Calcium Channels / Q000032:analysis / Q000502:physiology*; D002462:Cell Membrane / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure; D002478:Cells, Cultured; D008564:Membrane Potentials / Q000502:physiology; D009543:Nifedipine / Q000494:pharmacology; D010857:Pigment Epithelium of Eye / Q000737:chemistry / Q000166:cytology* / Q000502:physiology; D051381:Rats; D011922:Rats, Mutant Strains; D015222:Sodium Channels / Q000032:analysis / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology
D015220:Calcium Channels; D015222:Sodium Channels; D013779:Tetrodotoxin; D009543:Nifedipine