THIOL-DISULFIDE EXCHANGE SYSTEMS IN THE LIVER OF AGING FISCHER-344 RATS

The purpose of this study was to determine whether the major thiol-dis ulfide oxidoreductase activities of the rat liver were altered as a co nsequence of aging, and whether the alterations had any consequences i n terms of hepatic thiol concentrations. Liver fractions were prepared from male and female Fischer 344 rats at ages representing young adul thood (5 months), middle age (15 months) and old age (24-29 months), a nd the activities of the major thioldisulfide exchange enzymes, togeth er with protein and nonprotein sulfhydryl contents, were measured usin g spectrophotometric procedures. Thioltransferase, protein disulfide i somerase and thioredoxin reductase activities in livers of male and fe male rats were unchanged with aging, while glutathione disulfide (GSSG ) reductase activity remained the same (in male livers) or increased ( in female livers) as a consequence of aging. Both protein and nonprote in sulfhydryl concentrations were well maintained in old age. The abse nce of age-dependent alterations in the thiol-protein disulfide exchan ge enzymes and the lack of compromise in the glutathione GSSG reductas e system suggest that aged livers retain their capacity to regulate th eir thiol-disulfide redox balance under normal physiological condition s.