Muscular buffering capacity of the parr and smolts in Oncorhynchus masou

Abstract

Evidence suggests that muscular buffering capacity is important in control of the intracellular pH in white muscle during anaerobic burst swimming for prey capture or to escape from predators. The goal of this study was to compare the buffering capacity in the muscle of Oncorhynchus masou parr and smolts from a variety of sources. Levels of anserine, histidine and inorganic phosphate in the muscle, compounds that have strong buffering capacities, within the physiological pH range, and the buffering capacities of the white muscle between parr and smolts were compared. The anserine levels were significantly higher in smolts (19.5–22.5 μmol/g muscle) than in parr (11.5–18.5 μmol/g), while the histidine levels were lower in smolts (0.5–2.6 μmol/g) than in parr (3.2–5.0 μmol/g), within each source. The smolts tended to have higher levels of muscular inorganic phosphate (50.3–66.4 μmol/g) than the parr (47.2–61.5 μmol/g). The overall difference in the levels of these substances between the smolts and parr was reflected in their muscular buffering capacities, the white muscle of smolts having a significantly stronger buffering capacity than that of parr. These results suggest that the burst swimming ability might be enhanced in smolts compared to parr, or that the muscular buffering capacity of smolts may be elevated for coping with the recruitment of anaerobic energy production even at low swimming speed resulting from poor aerobic swimming ability.