The effects of in vitro ageing on the composition of the intracellular free amino acid pool of human diploid fibroblasts.

The composition of the free amino acid pool of the human diploid fibroblast cell line, BCL-D1, was analysed by automated ion-exchange chromatography throughout the life-span of the culture. Significant age-related changes, independent of growth effects, were found with six essential amino acids: a decrease in tyrosine, phenylalanine, leucine, isoleucine and valine, and an increase in methionine. The nature of the changes were suggestive of a decline in the operation of the L-system of amino acid transport with in vitro age. However, it is also possible that age-related changes in the proportions of tRNA iso-acceptors and/or the availability and accuracy of tRNA synthetases were involved.