Beta-alanine transport in the isolated hepatocytes of the elasmobranch Raja erinacea.

Cells were isolated from the liver of the skate and the uptake of beta-alanine followed using [14C]-beta-alanine. The isolated hepatocytes showed good viability, were found to accumulate beta-alanine from the incubation medium, and did so in a manner indicating a transport system involving a saturable carrier. The data for the rate of beta-alanine uptake suggest that this may be a rate-limiting step in the oxidation of the amino acid by the liver. Experiments indicated that the transport system could distinguish beta-alanine from certain structurally similar molecules (L-alanine and taurine, but not gamma-amino butyrate). Cells isolated from fish adapted to a diluted environment (50% seawater) showed no significant change in the uptake rate. However, evidence indicates that, over the range of beta-alanine concentrations occurring in the fish, the uptake rate would be acutely sensitive to small changes in the concentration in the blood, thus forming a self-regulating system for the metabolism of beta-alanine.