[Concentration of components of the adenylate system in heavy and light fractions of the sarcoplasmic reticulum of skeletal muscles and sensitivity of these fractions to the effects of imidazole-containing compounds and caffeine].
Fragments of sarcoplasmic reticulum from rabbit sceletal muscles sedimented within the range from 2000 g to 8000 g (heavy fraction) and 8000 g to 40000 g (light fraction) and washed with 0.6 M KCl, were practically free of adenylatecyclase activity. Phosphodiesterase cAMP was not found in the light fraction, while its activity in the heavy fraction was 500 pmol of cAMP/min per mg of protein. Both fractions contain bound cAMP (1-2 pmol/mg of protein) and specific sites of cAMP binding, the binding constant being approximately 10(6)M-1. The number of binding sites is 60 pmol/mg of protein for the heavy and 30 pmol/mg of protein for the light fractions. The level of phosphodiesterase activity in the heavy fraction correlates with its sensitivity to imidazole, anserine and caffeine. Imidazole and anserine increase in 1.5-1.8 times the value of Ca2+/ATP in the heavy fraction and produce no effect on Ca2+ transport by the light fraction. Caffeine decreases almost twice the Ca2+/ATP value in the heavy fraction and has practically no effect on Ca2+ absorption by enzymes of the light reticulum fraction. Imidazole and anserine activate membrane-bound phosphodiesterase, while caffeine inhibits it. It is suggested that structural rearrangements of membrane-bound phosphodiesterase under the effect of caffeine, imidazole and anserine are responsible for changes in the efficiency of Ca2+ transport by fragments of the heavy reticulum fractions.
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D000861:Anserine / Q000494:pharmacology; D001665:Binding Sites; D001693:Biological Transport, Active / Q000187:drug effects; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D004789:Enzyme Activation; D007093:Imidazoles / Q000494:pharmacology*; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000201:enzymology / Q000378:metabolism*
D007093:Imidazoles; D002110:Caffeine; D000242:Cyclic AMP; D010727:Phosphoric Diester Hydrolases; D000251:Adenosine Triphosphatases; D000262:Adenylyl Cyclases; D000861:Anserine; D002118:Calcium
Soderzhanie komponentov adenilattsiklaznoĭ sistemy v tiazheloĭ i legkoĭ fraktsiiakh sarkoplazmaticheskogo retikuluma skeletnykh myshts i chuvstvitel'nost' étikh fraktsiĭ k deĭstviiu imidazolsoderzhashchikh soedineniĭ i kofeina