Distribution of methionine between cells and incubation medium in suspension of rat hepatocytes

Methionine is an essential amino acid involved in many significant intracellular processes. Aberrations in methionine metabolism are associated with a number of complex pathologies. Liver plays a key role in regulation of blood methionine level. Investigation of methionine distribution between hepatocytes and medium is crucial for understanding the mechanisms of this regulation. For the first time, we analyzed the distribution of methionine between hepatocytes and incubation medium using direct measurements of methionine concentrations. Our results revealed a fast and reversible transport of methionine through the cell membrane that provides almost uniform distribution of methionine between hepatocytes and incubation medium. The steady-state ratio between intracellular and extracellular methionine concentrations was established within a few minutes. This ratio was found to be 1.06 +/- A 0.38, 0.89 +/- A 0.26, 0.67 +/- A 0.16 and 0.82 +/- A 0.06 at methionine concentrations in the medium of 64 +/- A 19, 152 +/- A 39, 413 +/- A 55, and 1,204 +/- A 104 mu mol/L, respectively. The fast and uniform distribution of methionine between hepatocytes and extracellular compartments provides a possibility for effective regulation of blood methionine levels due to methionine metabolism in hepatocytes.