EPIDERMAL GROWTH-FACTOR INDUCES THE DIFFERENTIAL RELEASE OF GP2 AND AMYLASE FROM AR4-2J CELLS

Epidermal growth factor (EGF) stimulates secretion of glycoprotein 2 (GP2) in a time- and concentration-dependent manner from the AR4-2J pancreatoma cell line. Cell differentiation induced by dexamethasone treatment for 3 d, however, did not significantly alter either basal or EGF-stimulated GP2 release. Basal and EGF-stimulated GP2 release were similarly unaffected by caerulein, which promotes amylase secretion by a regulated route. A brief exposure to cycloheximide profoundly blocked EGF-evoked GP2 secretion. Furthermore, EGF-stimulated GP2 release was not accompanied by significant alterations in intracellular ionic calcium levels, in contrast to the stimulatory actions of caerulein. We conclude that EGF-stimulated release of GP2 occurs via a novel secretory pathway that is neither regulated nor constitutive as currently defined.