RELATIONSHIP BETWEEN EPIDERMAL GROWTH-FACTOR IN MOUSE SUBMANDIBULAR GLANDS, PLASMA, AND BILE - EFFECTS OF CATECHOLAMINES AND FASTING

The epidermal growth factor (EGF) concentration in bile is high (simil ar to 150 fold higher than that in plasma), but little is known about its physiological control. Acute administration of the alpha 1-adrener gic agonist phenylephrine (1.7 mg/kg, iv) to male mice produced a rapi d increase in the EGF concentration in bile. We suggest that this EGF originates in submandibular glands and not in she liver. The bases for this are: 1) this increase was parallel to the increase in plasma, an d the EGF content of the submandibular glands decreased after phenylep hrine injection; and 2) the EGF concentrations in plasma and bile did not increase after phenylephrine administration to sialoadenalectomize d mice. The concentration of EGF in bile is not only under pharmacolog ical trations in plasma, bile, and submandibular glands increased in f asted mice. All of these changes were reversed by refeeding. As 1) [I- 125]EGF binding to liver membranes decreased only after 2 days of fast ing, but the level of circulating EGF was already increased in 1-day f asted mice, and 2) EGF secretion by submandibular glands from 1-day fa sted mice incubated in vitro increased, we suggest that the increase i n EGF concentrations in plasma and bile is the consequence of increase d endocrine secretion by submandibular glands. Taken together, our res ults suggest that there is a flux of EGF from submandibular glands to bile in mice, which is under physiological control.