Consumption and production of amino acids by insulin-responsive cultured fetal rat hepatocytes: the particular case of serine.

Abstract

The ability for 18-day fetal rat hepatocytes in primary culture to modify extracellular amino acid concentrations was studied between 24 and 48 h of culture. Most of the 19 amino acids tested were found to be taken up by the hepatocytes. However, serine and glutamate appeared in the 24-hour-conditioned medium to be twice as concentrated as in the fresh medium. The profile of net consumption or production of amino acids was unchanged when the medium was supplemented with essential amino acids. The use of [U-14C]glucose revealed that serine released in the medium was mainly formed from glucose. The presence of insulin (10 nM) did neither significantly modify the variations of amino acid concentrations in the medium nor 2-amino[1-14C]isobutyric acid uptake by the cells, while the hormone produced a 2-fold increase in glycogen labeling from [U-14C]glucose. This study revealed that whatever the regulatory culture conditions considered a net serine production out of the cells occurred, which appears to be specific to the fetal stage.