The respiratory and adenosinetriphosphatase activities of skeletal-muscle mitochondria

Abstract

Granules with respiratory activity were prepared from the skeletal muscles of various animals. The respiratory granules, mitochondria, of pigeon-breast muscle were studied in detail. Pigeon-breast mitochondria readily oxidized citrate, alpha-ketoglutarate, succinate, fumarate, and malate at 30[degree]. At 17[degree] pigeon-breast mitochondria oxidized pyruvate at very slow rates, but low concns. of malate or fumarate catalytically in-creased these rates. Myofibrils from rabbit-skeletal and pigeon-breast muscles had no oxidative activity. Oxidative phos-phorylation was demonstrated with pigeon-breast mitochondria. The highest P:O ratios were obtained when prepns. were carried out in the presence of 0.001 [image] ethylenediaminetetraacetic acid (EDTTA) and incubations in the presence of isotonic sucrose. Pigeon-breat mitochondria contain as ATPase which is activated to a greater extent by Mg than Ca. The Mg activated adenosine triphosphatase activity of mitochondria freshly prepared in the presence of EDTTA is increased by 2:4-dinitrophenol and by ageing at 0[degree]. The Mg-activated adenosine triphosphatase activity of mitochondria prepared with EDTTA is dependent on the tonicity of the incubation medium. Min. activity was obtained when the medium contained 0.2 [image]_sucrose.