Age related changes in the free amino acid pool of rat lens

Quite disparate values have been reported by various investigators for the concentrations of free amino acids in the normal rat lens. To test the possibility that the apparent discrepancies could result from age- or strain-related effects, assays were made on both weanling and mature specimens from two common laboratory strains of rats. Although the levels of free amino acids in the plasma were very similar in all groups, the total free amino acid concentration in the lenses of weanling rats was almost double that found in mature rats. Individual amino acids showed quite varied patterns of age-related changes in concentration. Although there is limited evidence that strain-related differences in the amino acid pool may also exist, it was concluded that age-related alterations probably account for most of the variation present in the previously reported values.