Effect of barium ions on excitation-contraction coupling of frog twitch muscle fibres.
The mechanism for the Ba2(+)-induced potentiation of the twitch tension in frog skeletal muscle was investigated. No significant difference in the peak amplitude of the calcium transients evoked by voltage-clamp depolarizing pulse was found between the fibres bathed in Ca2+ (control) and Ba2+ Ringer's solution, whereas the calcium transients evoked by the action potentials from the fibres in Ba2+ Ringer's solution were increased by about 64%, compared with control. In comparison with control, the action potentials of the fibres in Ba2+ Ringer's solution had a similar overshoot but a significantly longer time course. Our results suggest that excitation-contraction coupling in frog twitch muscle fibres is not altered by replacing Ca2+ with Ba2+. The Ba2(+)-induced potentiation of contraction may be accounted for by broadening of the action potentials.
Zhu
P H
PH
Department of Cellular and Molecular Neurobiology, Shanghai Institute of Physiology, Chinese Academy of Sciences, China.
Fu
D X
DX
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D001464:Barium / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects*; D009132:Muscles / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D011898:Ranidae / Q000502:physiology*
D001464:Barium; D002118:Calcium