[Effect of compound 48/80 on masseter muscle sarcoplasmic reticulum calcium transport system].
To define the role of calmodulin in Ca2+ fluxes behavior of canine masseter muscle sarcoplasmic reticulum (SR) vesicles, the effect of condensation product of N-methyl-p-methoxy-phenethylamine with formaldehyde (compound 48/80), a selective and powerful inhibitor of calmodulin-regulated function, on Ca(2+)-ATPase activity, oxalate-supported Ca2+ uptake velocity, and on interaction with Ca2+ permeability and Ca2+ loading at steady-state were evaluated. Compound 48/80, at concentrations of 10 to 100 micrograms/ml, reduced oxalate-supported Ca2+ uptake velocity without affecting Ca(2+)-ATPase activity. In the presence of 10 micrograms/ml compound 48/80, there was a shift of pH- or temperature-response curve of oxalate-supported Ca2+ uptake velocity, but not of Ca(2+)-ATPase activity, down. It was found that Arrhenius plots of the Ca(2+)-ATPase activity show a break at about 21 degrees C in the presence or absence of 10 micrograms/ml compound 48/80, and that compound 48/80 has no effect on Arrhenius plots of the oxalate-supported Ca2+ uptake velocity. Furthermore, Ca2+ loading at steady-state, but not passive Ca2+ permeability, was decreased by compound 48/80 at low concentrations (1-2 micrograms/ml). The results of this study suggest that calmodulin-dependent process plays a functional role in the coupling of ATP hydrolysis and Ca2+ accumulation, perhaps through regulation of Ca2+ release channels in masseter muscle SR membrane. Calmodulin-dependent component of Ca2+ fluxes in the SR vesicles may be directly modified by compound 48/80, thereby diminishing Ca2+ accumulation without affecting the Ca2+ uptake mechanism.
Odajima
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D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels; D002129:Calcium Oxalate; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000502:physiology*; D004285:Dogs; D008406:Masseter Muscle / Q000378:metabolism*; D010627:Phenethylamines / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*
D015220:Calcium Channels; D002147:Calmodulin; D010627:Phenethylamines; D002129:Calcium Oxalate; D002118:Calcium