title: Activation of phosphorylase by anoxia and dinitrophenol in rabbit colon smooth muscle: relation to release of calcium from mitochondria.
abstract: The effect of anoxia or 2,4-dinitrophenol (DNP) on the phosphorylase a activity and the calcium content in subcellular fractions from rabbit colon smooth muscle was studied. Anoxia for 15 min. as well as DNP (6.6 X 10(-5) M) for 5 min. increased the phosphorylase a activity. The calcium content in the mitochondrial subfraction, prepared from the anoxic- or DNP-treated intact muscle and determined by atomic absorption spectroscopy, was reduced. The calcium content in the nuclear and the microsomal fractions was not changed in preparations with a normal Ca-content. When the muscle was incubated for 60 min. in a Ca2+-free medium containing 2.0 mM EGTA, the calcium content in the mitochondrial fraction was reduced to 38% of the control. This calcium level was still further reduced and the phosphorylase a activity was increased by DNP in this "Ca-poor" muscle. In these preparations the Ca-content of the microsomal + supernatant fraction increased. Only when the muscle was incubated, initially, in an anoxic medium containing 0.1 mM Ca2+ for 120 min. and, subsequently, in an oxygenated medium containing 0.1 mM Ca2+ for 20 min., DNP failed to activate phosphorylase and to decrease the calcium content in the mitochondrial fraction. These results indicate that mitochondrial Ca2+ release is one of the regulatory factors of the anoxic-induced glycogenolysis.
mesh_terms: D019297:2,4-Dinitrophenol; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004140:Dinitrophenols / Q000494:pharmacology*; D004533:Egtazic Acid / Q000494:pharmacology; D003576:Electron Transport Complex IV / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D000860:Hypoxia / Q000201:enzymology*; D066298:In Vitro Techniques; D008931:Mitochondria, Muscle / Q000378:metabolism*; D009130:Muscle, Smooth / Q000187:drug effects / Q000201:enzymology*; D010762:Phosphorylase a / Q000378:metabolism*; D006005:Phosphorylases / Q000378:metabolism*; D011817:Rabbits; D013347:Subcellular Fractions / Q000201:enzymology
chemical_list: D004140:Dinitrophenols; D004533:Egtazic Acid; D003576:Electron Transport Complex IV; D010762:Phosphorylase a; D006005:Phosphorylases; D019297:2,4-Dinitrophenol; D002118:Calcium