Uptake and Metabolism of L-Alanine by Freshly Isolated Trout (Salmo Trutta) Hepatocytes: The Effect of Fasting Available to Purchase

Uptake and metabolism of L-alanine by freshly isolated trout hepatocytes has been analyzed. This amino acid is incorporated ‘uphill’ by different carriers, either Na⁺-dependent or Na⁺-independent. Na⁺-dependent uptake shows the characteristics of an ASC system on the basis of cation dependence and substrate preferences. The Na⁺-independent uptake is split between an L-cysteine-sensitive system and a non-saturable component. No uptake through system A has been found, suggesting that this carrier is lacking in trout hepatocytes. On the basis of inhibition by several preferred amino acids, L-alanine is not taken up through either the L or N systems.

Fasting induced changes in both the uptake of L-alanine and its metabolism to CO₂ and glucose. There was an increase in uptake that showed an inverse relationship with L-alanine plasma levels. Glucose production from L-alanine rose during food deprivation, while CO₂ production showed an initial increase, similar to that of glucose. At the end of the fasting time considered, however, there was a drop in CO₂ production, indicating a different kind of regulation for alanine oxidation and gluconeogenesis.