Cell-free protein synthesis by kidney from the aging female Fischer F344 RAT

This is the first report to describe and characterize a cell-free protein synthesis system derived from kidney tissue. The optimum conditions for [³H]valine incorporation into protein by the post-mitochondrial supernatant from whole kidneys were found to be: pH 6.9, 7.5 mM MgCl₂, 150 mM KCl, 10 mM ATP, and 2 mM GTP. The cell-free protein-synthetising activities of kidneys isolated from 4.5-, 7.5-, 22-, and 31-month-old female Fischer F344 rats were measured using the post-mitochondrial supernatant. A 73-87% decrease in cell-free protein synthesis was observed between 4.5 and 31 months of age. Both the cell sap and microsomal fractions of the kidney post-mitochondrial super-natant from old rats were less active in protein synthesis than these fractions from the kidneys of young rats. No age-related change in the activity of RNA-ase in the kidney post-mitochondrial supernatant was observed. Kidney ribosomes stripped of endogenous mRNA were found to be active in poly(uridylic acid)-directed polyphenylalanine synthesis. The effect of aging on the fidelity of translation was determined by measuring poly(uridylic acid)-directed [¹⁴C]-phenylalanine and [³H]leucine incorporation by kidney ribosomes isolated from rats of various ages. No age-related change in the fidelity of poly(uridylic acid) translation by kidney ribosomes was observed.