Title

Does intracellular metabolite diffusion limit post-contractile recovery in burst locomotor muscle?

Author Info

Stephen T. Kinsey, University of North Carolina - Wilmington
Pragyansri Pathi, Florida State University
Kristin M. Hardy, University of North Carolina - WilmingtonFollow
Amanda Jordan, Florida State University
Bruce R. Locke, Florida State University

Recommended Citation

Published in The Journal of Experimental Biology, Volume 208, January 1, 2005, pages 2641-2652.

NOTE: At the time of publication, the author Kristin M. Hardy was not yet affiliated with Cal Poly.

The definitive version is available at https://doi.org/10.1242/jeb.01686.

Abstract

Post-metamorphic growth in the blue crab entails an increase in body mass that spans several orders of magnitude. The muscles that power burst swimming in these animals grow hypertrophically, such that small crabs have fiber diameters that are typical of most cells (600μm). Thus, as the animals grow, their muscle fibers cross and greatly exceed the surface area to volume ratio (SA:V) and intracellular diffusion distance threshold that is adhered to by most cells. Large fiber size should not impact burst contractile function, but post-contractile recovery may be limited by low SA:V and excessive intracellular diffusion distances. A number of changes occur in muscle structure, metabolic organization and metabolic flux during development to compensate for the effects of increasing fiber size. In the present study, we examined the impact of intracellular metabolite diffusive flux on the rate of postcontractile arginine phosphate (AP) resynthesis in burst locomotor muscle from small and large animals. AP recovery was measured following burst exercise, and these data were compared to a mathematical reaction–diffusion model of aerobic metabolism. The measured rates of AP resynthesis were independent of fiber size, while simulations of aerobic AP resynthesis yielded lower rates in large fibers. These contradictory findings are consistent with previous observations that there is an increased reliance on anaerobic metabolism for post-contractile metabolic recovery in large fibers. However, the model results suggest that the interaction between mitochondrial ATP production rates, ATP consumption rates and diffusion distances yield a system that is not particularly close to being limited by intracellular metabolite diffusion. We conclude that fiber SA:V and O₂ flux exert more control than intracellular metabolite diffusive flux over the developmental changes in metabolic organization and metabolic fluxes that characterize these muscles.

Disciplines

Biology

Copyright

2005 Stephen T. Kinsey, Pragyansri Pathi, Kristin M. Hardy, Amanda Jordan and Bruce R. Locke.

Publisher statement

Published by The Company of Biologists.