L- and T-type voltage-gated Ca2+ currents in adrenal medulla endothelial cells.
We investigated voltage-dependent Ca2+ channels of bovine adrenal medulla endothelial cells with the whole cell version of the patch-clamp technique. Depolarization elicited an inward current that was carried by Ca2+ and was composed of a transient (T) current, present in all the cells tested, and a sustained (L) current, present in 65% of them. We separated these currents and measured their individual kinetic and gating properties. The activation threshold for T current was approximately -50 mV, and its maximum amplitude was -49.8 +/- 4.8 pA (means +/- SE, n = 19) at 0 mV. The time constant was 10.2 +/- 1.5 ms (n = 4) for activation and 18.4 +/- 2.8 ms (n = 4) for inactivation. The L current activated at -40 mV, and it reached a plateau at -20.1 +/- 2.3 pA (n = 6). Its activation time course was a single exponential with an activation time contant of 26.8 +/- 2.3 ms (n = 4). Current-voltage curves, kinetics, gating, response to BAY K 8644, nifedipine, amiloride, and different selectivity for Ba2+ and Ca2+ indicated that the underlying channels for the observed currents are only of the T- and L-types that resemble those of the endocrine secretory cells.
Vinet
R
R
Laboratory of Cell Biology and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA. rvinet@uv.cl
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D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000313:Adrenal Medulla / Q000166:cytology / Q000378:metabolism*; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D020746:Calcium Channels, L-Type; D020747:Calcium Channels, T-Type; D002417:Cattle; D004095:Dihydropyridines / Q000494:pharmacology; D004553:Electric Conductivity; D004594:Electrophysiology; D004727:Endothelium / Q000166:cytology / Q000378:metabolism; D015640:Ion Channel Gating / Q000502:physiology
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D020747:Calcium Channels, T-Type; D004095:Dihydropyridines; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000584:Amiloride