Gold ion inhibits silver ion induced contracture and activates ryanodine receptors in skeletal muscle.
Effects of Au3+ on Ag(+)-induced contractures and Ca2+ release channel activity in the sarcoplasmic reticulum were studied in frog skeletal muscles. Single fibres spontaneously produced phasic and tonic contractures upon addition of 5-20 microM Ag+ or more than 50 microM Au3+. Simultaneous application of 5 microM Ag+ and 20 microM Au3+ inhibited contractures induced by Ag+. Au3+ applied immediately after development of Ag(+)-induced contractures shortened the duration of the phasic contracture and markedly decreased the subsequent tonic contracture. Pretreatment of fibres with Au3+ inhibited the Ag(+)-induced phasic contracture. Ca2+ release channels incorporated into planar lipid bilayers were activated in response to Au3+ at 20 to 200 microM. A close relationship was observed between Ca2+ release channel open probability and amplitude of the Au(3+)-induced tonic contracture. Channel activity was inhibited by 5 microM ruthenium red. We conclude that extracellular Au3+ at low concentrations modifies the interaction of Ag+ with voltage sensors in the transverse tubules to inhibit the Ag(+)-induced contracture and, if it enters the cell, Au3+ may directly activate the sarcoplasmic reticulum Ca2+ release channel to partially contribute to the tonic contracture.
Department of Microbiology, Kyoto Prefectural Medical University, Japan.
K
K
Nihonyanagi
T
T
Oba
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels; D004553:Electric Conductivity; D006046:Gold / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D011892:Rana catesbeiana; D012519:Sarcoplasmic Reticulum / Q000187:drug effects; D012834:Silver / Q000037:antagonists & inhibitors* / Q000494:pharmacology
D015220:Calcium Channels; D012834:Silver; D006046:Gold; D002118:Calcium