Uptake and accumulation of amino acids in the brackish-water bivalve Corbicula japonica Prime during high salinity acclimation

Abstract

l-alanine in the external medium was taken up more rapidly by intact animals of the brackishwater bivalve Corbicula japonica Prime transferred from freshwater to 250 mOsm than to 2 mOsm. The animals transferred to 250 mOsm took up l-alanine at a rate comparable to that of elevation of the concentration of ninhydrin positive substances (NPS) in tissues. However, the tissue NPS accumulation in animals exposed to the increased salinity did not differ between the presence and absence of external l-alanine. When isolated gill and foot tissues were incubated under a hyperosmotic condition, accumulation of NPS was augmented by external l-alanine at concentrations as low as 0.5 mM. Such a remarkable augmentation by exogenous l-alanine was not found in the tissues incubated under the isosmotic condition. Uptake of amino acids appears to contribute, at least partly, to intracellular osmoregulation during high salinity acclimation.