AGING EFFECTS ON HEPATIC NADPH CYTOCHROME-P450 REDUCTASE, CYP2B(1-AND-2), AND POLYMERIC IMMUNOGLOBULIN RECEPTOR MESSENGER-RNAS IN MALE FISCHER-344 RATS

Aging perturbs the expression of many liver proteins, but the mechanis ms remain unresolved. Expression of hepatic NADPH cytochrome P450 redu ctase, phenobarbital-induced CYP2B1&2, and the polymeric immunoglobuli n receptor (pIgR) decline as a function of aging. We examined the effe ct of aging on the expression of the mRNA transcripts of these protein s, as well as those of alpha2u-globulin and beta-actin in male F344 ra ts. Despite age-related losses in the expression of P450 reductase and plasma membrane-bound pIgR in the rat liver (almost-equal-to 30-50%), aging is accompanied by 1) no change and 2) a modest decline (< 20%) in their respective mRNA steady state levels. On the other hand, the e xpression of phenobarbital-induced microsomal CYP2B1&2 and the steady state level of its mRNA exhibit parallel age-dependent shifts. The mRN A transcript for alpha2-globulin declines between maturity and old age , whereas the beta-actin mRNA level remains unchanged. These prelimina ry data are consistent with previous studies which suggest that aging may perturb hepatic CYP2B1&2 and alpha2-globulin at the transcriptiona l level, whereas changes in the expression of P450 reductase and pIgR may reflect posttranscriptional modifications.