Epidermal growth factor receptors during postnatal development of the mouse colon

The present study was undertaken to establish the postnatal profile of specific epidermal growth factor (EGF) binding in the maturing mouse colon, with particular emphasis on possible regional differences between both proximal and distal colonic binding patterns vs. those of the small intestine. Binding studies using [125I]EGF were performed on isolated epithelial cells obtained from 2-, 5-, 9-, 16-, and 22-day-old mice as well as adults. At 2 days, cells isolated from the entire colon bound 4 times more [125I]EGF than did corresponding intestinal cells, whereas between the ages of 5 days to adult, colonic cells bound between 1.7-2.5 times more labeled EGF than their intestinal counterparts. The immature colon already exhibited maximal binding after birth as opposed to the small intestine where binding only reached maximal values by the third week of life. Comparison between the proximal and distal colon in 9-, 16-, and 22-day-old mice revealed a further 2-fold increase in EGF binding in the distal colon compared to that in the proximal colon. Scatchard plots of [125I]EGF displacement by native EGF in both proximal and distal colonic segments also revealed the presence of two classes of binding sites, with high affinity constants (K1) significantly greater in the distal colon. These results demonstrate for the first time not only the continued presence of EGF receptors in mouse colonic epithelium, but also significant regional differences in EGF-binding capacity within the digestive tract throughout the postnatal period.