INTESTINAL-CELL RESPIRATION IS INFLUENCED BY ANIMAL AGE, STRAIN, AND FEEDING STATUS

The objectives of this study were to evaluate the influence of aging a nd the fasted vs fed state on substrate oxidation by jejunal and colon ic cells in vitro, and to determine whether the effects of these facto rs would be influenced by rat strain. Young (4 mo) and aged (24 mo) ma le rats of the Fischer 344 (F344) and Fischer x Brown Norway (F x BN) strains were used either following a 48-hr fast or in the ad libitum f ed state. On the morning of experimentation, cells were removed from s egments of the jejunum and colon and aliquots of these suspensions wer e incubated in 5 mM concentrations of substrates containing trace quan tities of C-14-labeled isotopes. Following 60 min of incubation, (CO2) -C-14 was collected and quantified to determine substrate oxidation. T he oxidation of glucose, glutamine, and 3-hydroxybutyrate was studied in jejunal and colonic cells, and the oxidation of acetate and butyrat e was studied in colonic cells only. Glucose oxidation by jejunal cell s was lower when cells were taken from 48-hr fasted animals than from fed animals, but the feeding status of the animal did not significantl y influence oxidation of other substrates by jejunal or colonic cells. Substrate oxidation was not different for the F344 vs F x BN strains when jejunal and colonic cells were taken from young animals. Differen ces due to rat strain became apparent in the aged animals, however, wi th oxidation of several substrates being higher for the aged F344 than for the aged F x BN animals. In particular, colonic cells from aged F 344 rats oxidized acetate, butyrate, and 3-hydroxybutyrate to greater extents than cells from young F344 rats, whereas differences due to ag e were not significant for the F x BN strain.