AbstractThe time course of alanine accumulation in vitro by body wall of the marine polychaete, Glycera dibranchiata, was studied in the presence and absence of sodium and metabolic inhibitors. Utilizing acute exposure‐retention techniques, the body wall was found to accumulate alanine against a 343:1 (tissue/sea water) concentration gradient at steady state when exposed to an amino acid concentration approximately that of its natural habitat (8.6 × 10−5 M). In the absence of sodium, or in the presence of the metabolic inhibitors 2,4‐dinitrophenol, sodium azide, and ouabain, the steady state alanine gradient is equal to unity. Accumulated alanine probaby resides intracellularly in the body wall, since the apparent extracellular space in body wall accounts for only 6% of the total tissue water. The 343:1 alanine gradient generated by the body wall is thermodynamically plausible in light of the proposed model of alanine influx in body wall epithelial membrane (Stevens and Preston, '80b). The energy available for such influx and accumulation can be derived directly from the sodium chemical gradient plus the membrane electrical potential or potassium gradient.