Effects of (+) and (-) enantiomers of calcium channel agonist, Bay K 8644, on mechanical and electrical responses of frog skeletal muscle.
The effects of (+) and (-) enantiomers of Bay K 8644, a Ca2+ channel agonist, on the mechanical and electrical properties of frog skeletal muscle fibers were investigated. In the concentration range of 10(-6) to 10(-5) M, both (+) and (-) enantiomers of Bay K 8644 significantly increased the maximum amplitudes of twitch responses. Both (+) and (-) enantiomers of Bay K 8644, at higher concentrations such as 10(-4) M, greatly depressed the amplitudes of twitches. Potentiating and depressing effects of (-) enantiomer of Bay K 8644 on twitch responses were significantly greater than those of the (+) enantiomer. At all concentrations used, both (+) and (-) enantiomers of Bay K 8644 significantly decreased the area under the tetanic force x time curve. In intracellular recordings, it was found that the depressing effects of both (+) and (-)-Bay K 8644 on tetanic contractions and twitch responses were due to the inhibition of action potentials. The inhibitory effect of (-) enantiomer of Bay K 8644 on action potentials also was significantly greater than that of the (+) enantiomer. In conclusion, present results suggest that, in contrast with cardiac muscle fibers, (+) and (-) enantiomers of Bay K 8644 have similar inhibitory effects on the electrical and mechanical properties of frog skeletal muscle fibers.
Oz
M
M
Loeb Research Institute, Ottawa Hospital, ON, Canada. moz@lri.ca
Tchugunova
Y
Y
Dinç
M
M
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology*; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002120:Calcium Channel Agonists / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000502:physiology; D011894:Rana pipiens; D013237:Stereoisomerism
D002120:Calcium Channel Agonists; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D002118:Calcium