Meeting Abstract

60.1  Tuesday, Jan. 6  Scaling with body mass of mitochondrial respiration in fish white muscle. BURPEE, Jessica L*; KINSEY, Stephen T; University of North Carolina Wilmington jlb7346@uncw.edu

White muscle in black sea bass (Centropristis striata) grows hypertrophically, and fiber sizes increase during development from <50 m in juveniles to >250 m in adults. This leads to increases in intracellular diffusion distances that may impact the scaling of metabolic properties. We have previously analyzed the scaling with body mass of aerobic capacity (mitochondrial volume density; b=-0.06), and the maximal rate of an aerobic process (post-contractile phosphocreatine recovery rate; b=-0.07) in isolated white muscle. In the present study, we examined the mass-specific scaling of state 3 respiration in isolated mitochondria in the presence of excess substrates (malate, pyruvate and ADP). In contrast to prior studies, these measurements are in no way limited by the diffusion of oxygen or metabolites to the mitochondria. The small scaling exponent of state 3 respiration (b=-0.004) was not significantly different from zero over a 50 fold range in body mass. This is consistent with the similar scaling exponents for mitochondrial volume density and phosphocreatine recovery rate, and implies essentially no effect of diffusion on metabolic rate, despite the long diffusion distances in these muscle fibers.