title: Reaction-diffusion analysis of the effects of temperature on high-energy phosphate dynamics in goldfish skeletal muscle.
abstract: Thermal acclimation results in dramatic changes in the fractional volume of mitochondria within skeletal muscle of teleost fish. We investigated the hypothesis that changes in mitochondrial volume represent a compensatory response to temperature-induced changes in intracellular diffusion coefficients (D) of the high-energy phosphate compounds ATP and creatine phosphate (PCr). Using 31P nuclear magnetic resonance spectroscopy, we determined DPCr and DATP in goldfish (Carassius auratus) skeletal muscle at 25 degrees C and 5 degrees C: DPCr was 3.28 +/- 0.18 x 10(-6) cm2s-1 at 25 degrees C and 2.00 +/- 0.90 x 10(-6) cm2s-1 at 5 degrees C: DATP was 2.13 +/- 0.16 x 10(-6) cm2s-1 at 25 degrees C and was estimated to be 1.30 x 10(-6) cm2s-1 at 5 degrees C. There was no evidence for an effect of acclimation temperature or fiber type on DATP or DPCr. A mathematical reaction-diffusion model was used to calculate profiles of [ATP], [PCr] and the free energy of ATP hydrolysis (delta GATP) in activated goldfish muscle fibers at 5 degrees C and 25 degrees C. The results showed spatial and temporal constancy of [ATP], [PCr] and delta GATP in red fibers at both temperatures, regardless of changes in acclimation temperature or mitochondrial density. The model also showed spatial and temporal constancy of [ATP] in white fibers at 5 degrees C and 25 degrees C, but gradients in [PCr] and delta GATP developed in white fibers under all conditions of temperature and acclimation temperature. These gradients were attenuated in cold-acclimated animals by cold-induced increases in mitochondrial density. However, the model shows that the proximal stimulus for temperature-induced changes in mitochondrial volume density in muscle is not a disruption in intracellular diffusion of high-energy phosphates.
authors.affiliation: Department of Biological Science, Florida State University, Tallahassee 32306-3050, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Hubley
authors.forename: B R
authors.initials: BR
authors.lastname: Locke
authors.forename: T S
authors.initials: TS
authors.lastname: Moerland
mesh_terms: D000064:Acclimatization; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D003402:Creatine Kinase / Q000378:metabolism; D004058:Diffusion; D006054:Goldfish / Q000378:metabolism*; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D008433:Mathematics; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism; D013696:Temperature; D013816:Thermodynamics
chemical_list: D010710:Phosphates; D010725:Phosphocreatine; D000255:Adenosine Triphosphate; D003402:Creatine Kinase