Epithelial cell proliferation and biodistribution of radiolabeled urogastrone in the gastrointestinal mucosa of young and old mice.

We have evaluated epithelial cell proliferation and biodistribution of radiolabeled recombinant human urogastrone/epidermal growth factor (125I rhUG/EGF) in the gastrointestinal mucosa of young (2+ months) and old (30+ months) mice. Animals were injected intraperitoneally with the metaphase arrest agent vincristine sulfate and intravenously with 125I rhUG/EGF. Animals were killed after two hours. Crypt cell production rate and uptake of radiolabeled urogastrone were measured in the same intestinal tissues. The results demonstrated that older animals had significantly greater crypt cell production rate as compared to young. However, the uptake of 125I rhUG/EGF was not significantly different (except in duodenum, where the uptake of 125I rhUG/EGF was significantly greater in young compared to old animals) between young and old animals. This suggests that increased epithelial cell proliferation in the aging animals is not associated with increased uptake of 125I rhUG/EGF. Thus epidermal growth factor/urogastrone may not be a primary factor for the intestinal kinetic differences which exist between young and old animals.