Demonstration of epidermal growth factor binding sites in the adult rat small intestine by autoradiography

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Abstract
The distribution of epidermal growth factor (EGF) receptors was studied in the distal portion of duodenum using light microscopic autoradiography performed at different time intervals (2–60 min) after intravenous injection of 125I-labelled EGF into adult rats. The results revealed a substantial binding of EGF to both cell types of the mucosal epithelium in duodenal crypts and villi, the columnar absorptive cells and the globet cells. Labelling was also found over few cells of lamina propria. No labelling was observed over the striated border of the duodenal mucosa epithelium. The time-course study performed in epithelial cells of duodenal crypts and villi showed that most silver grains were found at the periphery of the cells 2 min after injection. At the 7 min, silver grains were found both at the periphery and over the cytoplasm, more specifically the supranuclear region of the columnar absorptive cells. The number of grains overlying the cytoplasm of these cells was markedly reduced at 60 min. By quantitative autoradiography, maximal values were reached 7 min after the injection. Control experiments indicated that the autoradiography reaction was due to specific interaction of 125I-labelled EGF with its receptor. These results clearly indicate that EGF receptors are present in epithelial cells of the duodenal mucosa and suggest that the radioactive tracer is taken up by these cells.

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