Free amino acid profiles in blood during diving and recovery in the Antarctic Weddell seal

Abstract

The blood content of free amino acids was measured in the Antarctic Weddell seal (Leptonychotes weddelli) to assess their possible role in energy metabolism during simulated diving and recovery sequences. The total free amino acid pool size was similar to that in the common harbour seal and in man, but there were a few notable differences in amino acid contributions to the total pool. For example, in the Weddell seal alanine concentrations were unusually low. During diving, the content of free amino acids in whole blood changed hardly at all, unless glutathione levels also changed. In 5 of 10 dive sequences examined, glutathione was markedly depleted during diving, concomitant with a sharp rise in glutamate and glycine released on hydrolysis of this tripeptide. During recovery, glutathione levels were recharged quite rapidly. About half the glutamate and glycine expected from glutathione hydrolysis was expressed by elevated levels of these two amino acids; similarly, only a part of the glutathione reformed during recovery was represented by decreasing glutamate and glycine levels. The only other significant changes in amino acid levels during recovery were shown by alanine and glutamine, both of which increased in whole blood for periods of about 30–60 min. It was concluded that under most simulated diving conditions, free amino acid pools and profiles are not strongly perturbed. Metabolic conditions may arise, however, leading to large drops in glutathione levels, which in turn may perturb the free amino acid pool.