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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / pharmacology
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4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid
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4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / analogs & derivatives
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4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / pharmacology
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Adrenal Cortex / drug effects
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Adrenal Cortex / metabolism
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Adrenal Medulla / drug effects
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Adrenal Medulla / metabolism*
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Animals
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Calcium / metabolism*
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Carbachol / pharmacology
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Cattle
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Cell Membrane Permeability
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Ion Channels / metabolism*
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Kinetics
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Lead / metabolism*
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Mathematics
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Tetrodotoxin / pharmacology
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Veratridine / pharmacology
Substances
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Ion Channels
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4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid
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Lead
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Tetrodotoxin
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Veratridine
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3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester
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Carbachol
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4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid
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Calcium