Small Intestinal Crypt Cell Proliferation Rates Are Increased in Senescent Rats

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Abstract
Our previous studies implied that intestinal epithelial cell replication might be increased in senescent rats. Duodenal, jejuna!, and heal crypt cell production rates (CCPR) were measured in 3-4-mo and 26-28-mo female fed control, 3-day starved and 1-day refed, and in 4−5-mo and 26−28-mo male fed Fischer rats, using the vincristineinduced metaphase arrest technique. Fed aging rats had greater proximal intestinal crypt cell numbers which fell less during starvation than those of young controls. Metaphase accumulation also was higher in aging rat duodenum and jejunum, and CCPR were 30−100% more than in young rats. Starvation reduced CCPR by more than 40% in the duodenum of young, but only by 10% in older animals. Crypt proliferative patterns demonstrated a broadened proliferative zone in aging rats. These combined results directly demonstrate that small intestinal cell production is enhanced in senescent rats and that the nutritional controls of proliferation are blunted.