β-Alanine transport in the isolated hepatocytes of the elasmobranchRaja erinacea

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Abstract
Cells were isolated from the liver of the skate and the uptake of β-alanine followed using [14C]-β-alanine. The isolated hepatocytes showed good viability, were found to accumulate β-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 β-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 β-alanine from certain structurally similar molecules (L-alanine and taurine, but not γ-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 β-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 β-alanine.