Multiple types of Ca2+ channels in visceral smooth muscle cells.
Single-channel currents were recorded from two classes of Ca2+ channels in visceral smooth muscle cells isolated from the stomach of the toad, Bufo marinus: a class of small-conductance channels (approximately 11 pS) and a class of large-conductance channels (approximately 26 pS). Small-conductance channels were present in a majority of patches and gave rise to a slowly inactivating current (t1/2 approximately 250 ms at 0 mV). Openings of large-conductance channels could be unequivocally resolved only in the presence of the dihydropyridine Ca2+ agonist Bay K 8644. Two subtypes of the large-conductance channels were found--those with a very slow rate of decay (greater than 500 ms) and those with a faster one (less than 100 ms). Large-conductance channels resemble L-type Ca2+ channels of other preparations. Small-conductance channels do not fit unambiguously into the other existing categories (i.e., N or T). Correspondence between single-channel and macroscopic Ca2+ currents is discussed.
Vivaudou
M B
MB
Department of Physiology, University of Massachusetts Medical School, Worcester 01655.
Singer
J J
JJ
Walsh
J V
JV
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000378:metabolism; D002024:Bufo marinus; D015220:Calcium Channels / Q000378:metabolism*; D004095:Dihydropyridines / Q000494:pharmacology; D004553:Electric Conductivity; D005753:Gastric Mucosa / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D009130:Muscle, Smooth / Q000378:metabolism*; D013270:Stomach / Q000166:cytology
D015220:Calcium Channels; D004095:Dihydropyridines; D001464:Barium; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; C038806:1,4-dihydropyridine