Release and binding of epidermal growth factor in the pancreas of rats.

Abstract

Previous studies showed that EGF is produced by salivary and duodenal glands and released in saliva and duodenal secretion. Using specific radioimmunoassay of EGF, this study showed that the salivary glands and duodenal mucosa contain high levels of EGF, reaching, respectively, about 38 and 4 micrograms/g of tissue weight. EGF immunoreactivity was also found in high amounts in the pancreatic tissue (20 micrograms/g) and the pancreatic juice (32 ng/mL), where the content of EGF was found to increase in response to feeding, cholecystokinin, or bombesin and to decrease after the administration of atropine and somatostatin. Studies on the binding of EGF revealed that pancreatic acinar membranes possess the specific and saturable EGF receptors with a high affinity sites with Kd of about 4.3 nM and binding capacity of about 62 fmol/mg of protein, and with low affinity sites with Kd of 21 nM and binding capacity of about 180 fmol/mg of protein. The observed high content of immunoreactive EGF in the pancreatic tissue and the presence of high and low affinity binding sites for EGF in the pancreatic acinar membranes, as well as the high EGF output in the pancreatic juice and its alterations in response to hormonal and postprandial stimulation, suggest an important role of EGF in pancreatic physiology.