title: Lead enters bovine adrenal medullary cells through calcium channels.
abstract: Agents that stimulate secretion also accelerate the rate of Pb uptake into adrenal medullary cells. For example, when cells are suspended in a medium containing 5 microM Pb2+, depolarization by 77 mM K increases the rate of Pb uptake from 12 +/- 1 to 47 +/- 5 mumol/(L cells X min). K-induced Pb uptake has an apparent Km for Pb2+ of 2.6 microM, and is antagonized by Ca2+ with a K0.5 of 1.4 mM. The Ca channel blocker D-600 inhibits Pb entry with a K0.5 of 0.4 microM. Pb uptake is also stimulated by the Ca channel agonist BAY K 8644. These observations suggest that Pb passes through Ca channels. The permeability of the channels to Pb appears to be at least 10 times the permeability to Ca.
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000302:Adrenal Cortex / Q000187:drug effects / Q000378:metabolism; D000313:Adrenal Medulla / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002417:Cattle; D002463:Cell Membrane Permeability; D007473:Ion Channels / Q000378:metabolism*; D007700:Kinetics; D007854:Lead / Q000378:metabolism*; D008433:Mathematics; D013779:Tetrodotoxin / Q000494:pharmacology; D014701:Veratridine / Q000494:pharmacology
chemical_list: D007473:Ion Channels; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D007854:Lead; D013779:Tetrodotoxin; D014701:Veratridine; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D002217:Carbachol; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D002118:Calcium