Use of in vivo Whole-Body Autoradiography to Identify the Distribution of Epidermal Growth Factor Binding Sites under Normal Conditions in the Mouse Digestive System.

Abstract

The distribution of epidermal growth factor (EGF) binding sites in the mouse digestive system was investigated by in vivo whole-body autoradiography.Male mice were injected intravenously with 125I-EGF in both the absence and the presence of excess unlabeled EGF. The animals were perfused and subjected to autoradiographic procedures 3, 5, 15, and 30 min after injection. Our study provides the first quantitative data on the binding levels of digestive system tissues under in vivo conditions with intact experimental mice.Specific EGF binding was observed in the liver, pancreas, stomach, and intestinal mucosae at 3, 5, and 15 min post-injection, but at 30 minutes the bindings were not lowered by the presence of excess unlabeled EGF. Very high specific EGF binding was noted in the liver, where distribution of the binding sites was heterogeneous, and the density of the binding was higher around the branches of the portal vein than around the central vein. In the stomach, relatively high specific binding was seen in the glandular part, but the non-glandular portion showed no significant binding. There was low specific binding in the pancreas and distribution of that binding was homogeneous according to macroscopic observation. Low specific binding was observed in the intestinal tract from duodenum to rectum, and level of the binding was quite similar throughout the tract. The esophagus evinced no substantial EGF binding. Submandibular and sublingual glands showed relatively high radioactivity during the experimental period, but most of it was nonspecific in nature.

Autoradiographic distribution of radioactivity from 14C-GABA in the mouse

“…Indeed, there are plenty of papers indicating the presence of GABA receptors in peripheral tissues including superior cervical ganglion (Farkas et al, 1986), kidney (Amenta et al 1988;Erdö, 1990), adrenal gland (Castro et al, 1989;Martinez et al, 1987), liver (Minuk et al, 1987), urinary bladder (Erdö et al, 1989b), pancreas (Rorsman et al, 1989), stomach (Erdö et al, 1989aNakajima et al, 1996), and intestine (Gentilini et al, 1992;Nakajima et al, 1996). Whole body autoradiographic technique used in the present study was not sensitive enough to distinguish the cells containing GABA receptors, though the technique had proven to be a powerful tool for investigating the tissue distribution of insulin (Watanabe et al, 1992), glucagon (Watanabe et al, 1997b), and epidermal growth factor (Nishihara et al, 1994) receptors. The cellular distribution of GABA receptors should be made by light microscopic autoradiography that provides more sensitivity and resolution (Hirose et al, 1994;Shimada and Watanabe, 1997;Watanabe et al 1997aWatanabe et al , 1998.…”