Albumin synthesis in cultured hempatoma cells. Regulation by essential amino acids.

The effects of essential amino acids on albumin synthesis by a mouse hepatoma cell line have been investigated. The amino acids tested were tryptophan, phenylalanine, histidine, isoleucine and leucine. Cellular rates of synthesis (molecules albumin/cell per min) were determined from rates of [3H]leucine incorporation into immunoprecipitable albumin in the culture medium. The effects of amino acids on albumin synthesis fall into three distinct groups. The concentration of tryptophan producing half-maximal synthesis is 4 micronM. The corresponding concentration for leucine is 100 micronM. Histidine, phenylalanine and isoleucine were very similar, the half-maximal concentrations being approximately 15 micronM. The concentrations of amino acids producing half-maximal synthesis correlate directly with the amino acid composition of albumin. The levels of these essential amino acids necessary to saturate albumin synthesis have been compared with amino acid levels in normal plasma.