125I-endothelin binds to fibroblasts beneath the epithelium of rat small intestine.

Rats were intravenously injected with synthetic 125I-endothelin, and then were fixed by intracardiac perfusion at 10 min, 30 min and 1 hr after the injection. Localization of 125I-endothelin was examined in the small intestine by light and electron microscopic radioautography. Through the time course examined, more than seventy percent of total silver grains were localized in the fibroblasts, especially beneath the basal lamina of epithelium of the intestinal villi. Silver grains were observed mostly on the thin processes, and also on the vacuoles. At 10 min, 80% of silver grains on the fibroblasts were located on the plasmalemma. By the chase, grains on the plasmalemma decreased, and silver grains in the cytoplasm increased gradually.