Buffering capacity of vertebrate muscle: Correlations with potentials for anaerobic function

Summary Buffering capacities (), measured in slykes (moles of base required to titrate the pH of one gram wet weight of muscle by one pH unit, over the pH range of pH 6 to pH 7) due to non-bicarbonate buffers were measured in locomotory muscles from a variety of terrestrial and marine mammals and teleost fishes (Tables 1 and 2). The highest buffering capacities were found in muscles capable of either intense, burst glycolytic function or prolonged, low-level anaerobic function. Marine mammals had higher muscle buffering capacity on the average than terrestrial mammals. Among the fishes studied, warm-bodied species had the greatest values of all animals examined (Table 2). Deep-sea fishes and shallow-living fishes with sluggish locomotory abilities had low values. Fish white muscle displayed higher buffering capacity than red muscle (Fig. 1; Table 2), in keeping with the more aerobic poise and higher capillary density of the latter type of muscle. Strong correlations were found between (1) and muscle myoglobin concentrations in the mammalian species (Table 1; Fig. 2), and (2) and muscle lactate dehydrogenase (LDH) activities in both the mammals and the fishes (Tables 1 and 2; Fig. 3). No correlation was found between and the activity of a citric acid cycle indicator enzyme, citrate synthase, in the mammalian species. While strongly correlated with buffering capacity, the amounts of myoglobin and LDH in a muscle are not the principal determinants of . The results indicate that muscle intracellular buffering capacity is especially critical in locomotory muscles which must function under conditions (burst locomotion and prolonged, low-level anaerobic function) where circulatory perfusion is inadequate to rapidly remove the acidic end-products such as lactic acid that are produced by anaerobic glycolysis. In this respect, the locomotory muscle of diving mammals and the white skeletal muscles of teleost fishes face a common acid-base regulatory problem and utilize a common biochemical strategy to resolve it.