Meeting Abstract
P2.104 Jan. 5 AK and AMPd activity and modified high energy phosphate set points in mice acclimated to hypoxia OVERTON, J.D.*; ADAMS, G.S.; MCCALL, R.D.; KINSEY, S.T; UNCW; UNCW; UNCW; UNCW jdo5910@uncw.edu
Differences in hypoxic exercise tolerance (HET) previously have been found in two inbred strains of mice, Balb/cByJ (C) and C57BL/6J (B6), and their F1 hybrid following exposure to hypobaric hypoxia (McCall and Frierson, 1997). Performance differences of these mice under hypoxic conditions were predominantly associated with two epistatically interacting loci of major effect and an unknown number of modifying genes (McCall et al. 1998). Korzeniewski (2006) proposed that flux through adenylate kinase (AK) and AMP deaminase (AMPd) reduces anaerobic glycolysis during heavy exercise and/or hypoxia while also inducing a decrease in the adenylate pool. This reduced anaerobic glycolysis results in decreased proton production, and thus acts as a defense against fatigue during exercise. 31P-nuclear magnetic resonance (NMR) was used to examine relative concentrations of phosphocreatine (PCr), ATP, and Pi, in the predominantly slow-twitch soleus (SOL) and predominantly fast-twitch extensor digitorum longus (EDL). Absolute concentrations of ATP and Cr were measured using reverse phase high performance liquid chromatography (rp-HPLC) and AK and AMPd activity were measured spectrophotometrically. The SOL and EDL in mice acclimated to hypoxia had increased ATP/Pi and PCr/Pi ratios, and lowered PCr/ATP ratios. These changes in HEP compounds during hypoxia acclimation were not associated with changes in muscle fiber type, myosin heavy chain isoform composition, muscle capillarity, or muscle contractile properties. Also, mice acclimated to hypoxia had a decreased adenylate pool, which is consistent with the hypothesis that hypoxia acclimated mice have an increase reliance on AK and AMPd. However, there were no significant differences in AK or AMPd activities among strains acclimated to hypoxia.
