Inhibition of Zn2+-induced potentiation of twitch tension by Ni2+ in frog muscle.
Effect of Ni2+ on Zn2+-induced potentiation of twitch tension was studied electrophysiologically in the toe muscle fibers of Rana catesbeiana. The major findings of this investigation are as follows. When 2 mM Ni2+ was applied to fibers in a normal Ringer's solution containing 50 microM Zn2+ (Zn2+ solution), the Zn2+-potentiated twitch tension decreased remarkably to about one-third of that before Ni2+ treatment. This concentration of Ni2+ caused a 23% decrease in the duration of action potential which had been prolonged by Zn2+ (6.61-5.09 ms). Ni2+ (2 mM) added to normal Ringer's solution led to increases of about 30 and 42% in twitch tension and in the duration of action potential, respectively. A slight increase in the mechanical threshold was induced by 2 mM Ni2+. The inhibitory action of Ni2+ on the twitch tension in Zn2+ solution was larger than that in the case of tetanus tension. Diltiazem (40 microM), a Ca2+ channel blocker, did not inhibit the twitch tension potentiated in Zn2+ solution. These results suggest that the decrease in Zn2+-potentiated twitch tension by Ni2+ may possibly derive from impairment of the propagation of action potential along the T tubules.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001696:Biomechanical Phenomena; D004056:Differential Threshold; D004110:Diltiazem / Q000494:pharmacology; D004357:Drug Synergism; D009119:Muscle Contraction / Q000187:drug effects*; D009532:Nickel / Q000494:pharmacology*; D011892:Rana catesbeiana; D014034:Toes; D015032:Zinc / Q000037:antagonists & inhibitors* / Q000494:pharmacology
D009532:Nickel; D004110:Diltiazem; D015032:Zinc