Bay K 8644 enhances Ca2+ channel activities in embryonic chick heart cells without prolongation of open times.
The effects of the Ca2+ channel agonist, Bay K 8644, on the slow (L-type) Ca2+ channels was examined in young (3-day-old) embryonic chick heart cells, which naturally exhibit long-lasting openings. Bay K 8644 (5 microM) increased (a) the peak amplitude of the ensemble-averaged current by 3.9 +/- 0.9-fold (mean +/- S.E.) and (b) the maximal number of simultaneous opening from 2.6 +/- 0.4 to 4.4 +/- 0.9. Bay K 8644 had no effect on the unitary conductance (27 pS in control), and relatively little effect in the open-close kinetic analysis. The mean open times were 4.2 ms and 5.2 ms, in control and Bay K 8644, respectively. These results suggest that the agonistic effect of Bay K 8644 involves a mechanism other than open-time prolongation, such as activation of silent channels.
Tohse
N
N
Department of Physiology and Biophysics, University of Cincinnati, College of Medicine, OH.
Conforti
L
L
Sperelakis
N
N
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000502:physiology; D015220:Calcium Channels / Q000187:drug effects*; D002478:Cells, Cultured; D002642:Chick Embryo; D006321:Heart / Q000187:drug effects; D009206:Myocardium / Q000166:cytology; D013268:Stimulation, Chemical
D015220:Calcium Channels; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D002118:Calcium