Tension development in frog skeletal muscle induced by silver ions.
In single fibers of frog toe muscles placed in a Cl- free MOPS solution containing 1.8 mM Ca2+, tension developed slowly in the presence of very low concentrations of Ag+. This tension was not blocked by the administration of Co2+ or Ni2+. On the other hand, two types of transient tensions developed with the application of 5 microM Ag+, in fibers pretreated with 0-Ca2+ MOPS solution, containing either 2 mM Co2+ or 1mM Ni2+, for 10 min. In the presence of divalent cations or TTX, the first repetitive twitch-like contraction disappeared, indicating this tension is induced by action potentials repeatedly generated by the lack of divalent cations. The 2nd subsequent transient tension was caused by 5 microM Ag+ in the presence of various kinds of divalent cations, or TTX. After reversion to the resting tension, the fiber was contracted by adding more than 0.1 mM of Ca2+ or 25 mM caffeine to the external medium. Even when placed in a Ca2+-free solution containing 3 mM EGTA and 3 mM Mg2+ for 30 min, the fiber still developed an appreciable tension in response to 5 microM Ag+. These findings suggest that a transient development of the Ag+-induced tension does not require the presence of external Ca2+. A specific sulfhydryl reagent, pCMPS, did not contract the muscle fiber. Therefore, Ag+ may develop tension by mediating unknown chemical reaction(s) other than the sulfhydryl group on T-tubular membrane proteins.
D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D003035:Cobalt / Q000494:pharmacology; D003472:Curare / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009132:Muscles / Q000187:drug effects / Q000502:physiology*; D009532:Nickel / Q000494:pharmacology; D011892:Rana catesbeiana; D012834:Silver / Q000494:pharmacology*; D013779:Tetrodotoxin / Q000494:pharmacology
D003035:Cobalt; D012834:Silver; D013779:Tetrodotoxin; D002731:4-Chloromercuribenzenesulfonate; D009532:Nickel; D003472:Curare; D008274:Magnesium; D002118:Calcium