title: Effects of methylxanthines on superprecipitation of myosin B extracted from rabbit fast skeletal muscle.
abstract: Myosin B was extracted from rabbit fast skeletal muscle. Caffeine (2-70 mM), theophylline (2-30 mM), and theobromine (2 mM) were examined for their effects on the rate and extent of myosin B superprecipitation at a low ionic strength (50 mM KCl) and a low concentration of ATP (40 microM) by the turbidimetric method. The rate of the superprecipitation was significantly (p less than 0.05 and p less than 0.01) reduced by 30-70 mM caffeine and 2-30 mM theophylline, while the extent was significantly (p less than 0.01) increased by 10-30 mM theophylline. The onset of the superprecipitation was also delayed and a clearing phase was even induced by 50-70 mM caffeine. Theobromine had no significant effect on the rate or extent of the superprecipitation at the concentration used. These results indicate that caffeine and theophylline are retardants of the myosin B superprecipitation reaction in the concentration ranges investigated.
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D011232:Chemical Precipitation; D009124:Muscle Proteins / Q000302:isolation & purification*; D009132:Muscles / Q000032:analysis*; D009218:Myosins / Q000302:isolation & purification*; D011817:Rabbits; D012995:Solubility; D013805:Theobromine / Q000494:pharmacology; D013806:Theophylline / Q000494:pharmacology; D014970:Xanthines / Q000494:pharmacology*
chemical_list: D009124:Muscle Proteins; D014970:Xanthines; D002110:Caffeine; D013806:Theophylline; D009218:Myosins; D013805:Theobromine