Apolipoprotein E is increased in aged rat kidney.

There is growing evidence to indicate that apolipoprotein (apo) E may be associated with age-related disorders and altered longevity in humans. Using rats as a model, we measured apoE in plasma, brain, heart, kidney, liver and spleen in aged (24-25 mo) and younger rats (6-8 mo). The results disclosed that: (a) the plasma concentrations of immunoreactive apoE in aged rats were higher than those in young animals by 70% (P < 0.01); (b) there was no age-related difference of apoE in the brain, heart, liver or spleen; (c) in contrast, the concentrations of apoE in the kidney of aged rats were markedly higher than those of young animals by 490% (P < 0.01). Our data suggest that, in the rat, age-related change in the organ concentrations of apoE is heterogeneous, and the selective increase in the kidney may have physiologic importance which merits further study.