Studies on isolated mitochondria from muscles of normal and dystrophic chickens

Abstract

Oxidative phosphorylation was studied in mitochondria from different fiber types in normal (line 412) and dystrophic (line 413) chickens in vitro. Three types of muscles, namely, superficial pectoralis (αW), lateral adductor (βR), and medial adductor (αR) were used. Mitochondria from adductor muscles of both normal and dystrophic chickens equally utilized a variety of substrates such as pyruvate-malate, succinate, β-hydroxybutyrate, and l-glutamate with the coupled phosphorylation of ADP. These organelles did not oxidize α-glycerophosphate with coupled ATP synthesis. However, the organelles from pectoralis muscles oxidized α-glycerophosphate and oxygen consumption in the presence of this substrate was repeatedly stimulated by the addition of limited quantities of ADP. The rate of oxidation of this substrate was significantly lower in dystrophic mitochondria as compared to normal organelles. Although, the organelles from dystrophic pectoralis muscles oxidized pyruvate-malate, succinate, and β-hydroxybutyrate with the same efficiency as normal muscle mitochondria, the rate of l-glutamate oxidation was lower than normal. All the isolated organelles oxidized NADH at a very slow rate and this oxidation was not coupled with the phosphorylation of ADP. Unlike results previously reported by many investigators, there was no difference in the yield of mitochondria from dystrophic muscle, but the cytochrome oxidase activity of dystrophic muscle homogenates was higher than that of normal muscle. These data strongly suggest the existence of an abnormality in the NADH “shuttle systems” of dystrophic pectoralis muscle mitochondria.