Metabolic changes in skeletal muscle and blood of greyhounds during 800-m track sprint

The aim of this study was to examine some metabolic properties and changes that occur in skeletal muscle and blood of greyhounds after an 800-m sprint. Three prime moving fast-twitch muscles were selected: biceps femoris (BF), gastrocnemius (G), and vastus lateralis (VL). The amount of glycogen utilized during the event was 42.57, 43.86, and 42.73 mumol glucosyl units/g wet wt, respectively. Expressed as a function of race time (48.3 +/- 0.7 s, n = 3), the mean rate of glycogen breakdown was 53.48 +/- 0.5 mumol.g wet wt-1.min-1 during the sprint. This is equivalent to an ATP turnover of 160 mumol.g wet wt-1.min-1, assuming 100% anaerobic conversion to lactate. This represents a conservative estimate, since greyhound muscle is heterogeneous and comprised of a large percentage of fast-twitch oxidative fibers (Armstrong et al., Am. J. Anat. 163: 87-98, 1982). The large decrease in muscle glycogen was accompanied by a 6- to 7-fold increase in muscle lactate from 3.48 +/- 0.13 to 25.42 +/- 3.54 (BF), 2.54 +/- 1.05 to 18.96 +/- 2.60 (G), and 4.57 +/- 0.44 to 30.09 +/- 1.94 mumol.g wet wt (VL), and a fall in muscle pH from 6.88 +/- 0.03 to 6.40 +/- 0.02 (BF), 6.92 +/- 0.02 to 6.56 +/- 0.02 (G), and 6.93 +/- 0.02 to 6.47 +/- 0.01 (VL). Cytosolic phosphorylation potential in BF decreased 10-fold from 11,360 +/- 680 to 1,184 +/- 347, and redox potential decreased 5-fold, indicating a marked reduction in the cytosol at this time.(ABSTRACT TRUNCATED AT 250 WORDS)