Abstract
We have studied the influence of the ageing phenomenon on metabolite absorption by the small intestine and the kidney of the rat, using isolated brush-border membrane vesicles prepared from 2 groups, one composed of 2 month, and the other of 24 month, animals. “Overshoot”, which is typical of Na +-glucose cotransporter activity, disappeared in the duodenum and decreased in the kidney of the old rats. Short-circuiting of vesicles with valinomycin showed that, in the presence of K + and valinomycin, “overshoot” decreased in both groups by about the same percentage. The Na +-dependent uptake of aspartate and phenylalanine showed contrasting pictures in the jejunum and kidney of the aged animals: aspartate transport decreased only in the kidney, while phenylalanine uptake was negatively affected in the jejunum. Na +-dependent citrate uptake, studied in renal brush-border membrane vesicles, was lower in the old rats. The K m values determined for Na +-dependent d-glucose and citrate uptake in the kidney did not meaningfully differ between the two groups. A continuous decrease in Na +-dependent d-glucose and citrate uptake in the rat kidney, during ageing, was demonstrated.
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