Multiple conductance levels of the dihydropyridine-sensitive calcium channel in GH3 cells.
Calcium channels in GH3 cells exhibit at least five conductance levels when examined in cell-attached or outside-out patches. These channels resemble the high threshold Ca2+ current in their range of activation and inactivation, and in their sensitivity to dihydropyridines (DHP). Mean open times for the five levels were brief (less than 1 msec) in control solutions but increased in the presence of BAY K 8644. In 100 mM Ba2+ and BAY K 8644, the five predominant slope conductances were 8-9, 12-13, 16-18, 23-24, and 28 pS. The present study is the first report of multiple levels of the DHP-sensitive Ca2+ channel occurring with high frequency in native membranes. The range of conductance levels that we observed encompasses the range of conductances found for two other different types of Ca2+ channels and indicates that unit conductance should be used with caution as a distinguishing characteristic for identification of different channel types.
Kunze
D L
DL
Department of Physiology and Molecular Biophysics, Baylor College of Medicine, Houston, Texas 77030.
Ritchie
A K
AK
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology*; D015220:Calcium Channels / Q000378:metabolism*; D002460:Cell Line; D004095:Dihydropyridines / Q000494:pharmacology*; D004553:Electric Conductivity; D006801:Humans; D009553:Nimodipine / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism*
D015220:Calcium Channels; D004095:Dihydropyridines; D009553:Nimodipine; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; C038806:1,4-dihydropyridine