Epidermal Growth Factor Receptors in Isolated Adult Mouse Intestinal Cells: Studiesin Vivoand in Organ Culture*

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Abstract
In isolated intestinal cells from adult fed mouse, the binding of [125I] epidermal growth factor (EGF) was time- and temperature-dependent. Maximum binding was obtained after 30 min of incubation at 20.degree. C. For a concentration of 5 .times. 10-11 M [125I]EGF (180 .mu.Ci/.mu.g), specific binding for isolated cells from duodenum, jejunum and ileum was closely similar, with means of 9.4 .+-. 0.9, 13.3 .+-. 0.8, and 9.3 .+-. 2.0%/mg protein, respectively. The binding increases along the crypt-villus axis. Inhibition dose-response analysis indicated high affinity binding with 50% inhibition at 3 .times. 10-10 M unlabeled EGF. The specific binding decreased by 19% after 48 h of fasting. In the P1 fraction (microsome and lateral membranes) from scrapings or isolated cells of the jejunal mucosa, specific binding was 2.4 .+-. 0.8 and 6.5 .+-. 0.7%/mg protein, respectively. In the P2 fraction (brush border), specific binding was 6.9 .+-. 1.6% and 16.3 .+-. 0.7%/mg protein. After 24 h of organ culture, specific binding is not modified in duodenal explants. In the presence of EGF (500 ng/ml) in the culture medium, the binding is decreased by 72%. These results show, apparently, isolated intestinal cells from adult mice possess a high concentration of EGF receptors that exhibit kinetic properties identical to those of other EGF target cells. Unlike insulin receptors, EGF receptors are numerous on the intestinal brush border and in intestinal crypts and decrease by fasting.