Permeation of Pb2+ through calcium channels: fura-2 measurements of voltage- and dihydropyridine-sensitive Pb2+ entry in isolated bovine chromaffin cells.
Fura-2 was used to monitor Pb2+ entry into isolated bovine chromaffin cells exposed to micromolar concentrations of Pb2+ in media containing basal or high concentrations of K+. The entry of Pb2+ consists of voltage-independent and voltage-dependent (K(+)-stimulated) components. The voltage-dependent Pb2+ entry is enhanced by Ca2+ channel agonist BAY K 8644 and blocked by the channel antagonist nifedipine, suggesting the involvement of the L-type Ca2+ channels. In contrast to the transient, K(+)-depolarization-dependent increase in [Ca2+]i, the increase in [Pb2+]i is sustained over a period of several minutes, suggesting the absence of channel inactivation and/or the saturation of Pb(2+)-buffering capacity of the cell cytosol.
Tomsig
J L
JL
Department of Physiology and Biophysics, University of Cincinnati, College of Medicine, OH 45267-0576.
Suszkiw
J B
JB
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000313:Adrenal Medulla / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D002417:Cattle; D002463:Cell Membrane Permeability / Q000187:drug effects*; D002469:Cell Separation; D004095:Dihydropyridines / Q000494:pharmacology*; D016257:Fura-2; D007854:Lead / Q000378:metabolism* / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology
D015220:Calcium Channels; D004095:Dihydropyridines; D007854:Lead; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; C038806:1,4-dihydropyridine; D009543:Nifedipine; D016257:Fura-2