Potentiation of sarcoplasmic reticulum Ca2+ release by 2,3-butanedione monoxime in crustacean muscle.
The effect of the chemical phosphatase 2,3-butanedione monoxime (BDM) on various aspects of excitation/contraction coupling in crustacean muscle was investigated. Despite having a depressant effect on vertebrate skeletal and cardiac muscle, BDM was a potentiator of contraction in crustacean muscle. At concentrations of 1-3 mM BDM caused an increase of potassium contractures in bundles of fibers isolated from crayfish muscle. At higher concentrations BDM caused oscillatory contractions by itself. In single voltage-clamped cut muscle fibers loaded with rhod-2, BDM (0.5-2 mM) potentiated the magnitude and duration of intracellular Ca2+ transients elicited by depolarization. At the same time BDM did not affect the rate of Ca2+ removal from the myoplasm under conditions where Ca2+ release was blocked by tetracaine. Nor did BDM increase Ca2+ entry; in fact it caused a decrease in the amplitude of the inward Ca2+ current (ICa). In microsomes isolated from lobster muscle, BDM also potentiated Ca2+ release induced by caffeine and at higher concentrations (above 3 mM) induced release by itself. At the same time it had little effect on Ca2+ uptake. These results indicate that BDM potentiates Ca2+ release in crustacean muscle possibly by dephosphorylation of the Ca(2+)-release channel.
Györke
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S
Department of Physiology and Biophysics, University of Texas Medical Branch, Galveston 77550.
Dettbarn
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C
Palade
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P
D000818:Animals; D003400:Astacoidea / Q000378:metabolism*; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003931:Diacetyl / Q000031:analogs & derivatives* / Q000494:pharmacology; D004357:Drug Synergism; D004553:Electric Conductivity; D004594:Electrophysiology; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects; D009132:Muscles / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D011188:Potassium / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D013748:Tetracaine / Q000494:pharmacology
D013748:Tetracaine; C004717:diacetylmonoxime; D002110:Caffeine; D003931:Diacetyl; D011188:Potassium; D002118:Calcium