Nitrendipine block of calcium channel currents in vascular smooth muscle and adrenal glomerulosa cells.
Nitrendipine block of calcium channel currents has been characterized using patch clamp recording from bovine adrenal glomerulosa cells and aortic vascular smooth muscle cell lines A7r5 and A10. Each preparation contains two distinct populations of voltage-dependent calcium channels. The slowly inactivating (L) channel in each preparation activates with strong depolarizations, deactivates rapidly, and is more susceptible to nitrendipine block. L channels predominate in vascular smooth muscle and may underlie maintained calcium influx during high potassium induced contractures. The second channel type (T) activates with weak depolarizations from hyperpolarized potentials, inactivates rapidly, deactivates slowly, and is less susceptible to nitrendipine block. T channels carry much of the calcium channel current in glomerulosa cells and may mediate stimulus-secretion coupling in these cells. The relative contribution of each channel type to inward calcium channel current has been separated by holding potential and corresponding rates of deactivation. Contraction of vascular smooth muscle is much more potently blocked by nitrendipine than is stimulus-secretion coupling in adrenal glomerulosa cells or other endocrine tissues. This difference may reflect the predominance of different calcium channel types in different tissues.
McCarthy
R T
RT
Miles Institute for Preclinical Pharmacology, West Haven, Connecticut 06516.
Fry
H K
HK
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D002121:Calcium Channel Blockers; D002417:Cattle; D002478:Cells, Cultured; D004594:Electrophysiology; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009568:Nitrendipine / Q000494:pharmacology*; D051381:Rats; D015384:Zona Glomerulosa / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D002121:Calcium Channel Blockers; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009568:Nitrendipine