Cell Membrane Receptors for Secretagogues on Pancreatic Acinar Cells

Abstract

Publisher Summary This chapter provides an overview of cell membrane receptors for secretagogues on pancreatic acinar cells. The initial step in the mechanism of action of secretagogues on enzyme secretion from pancreatic acinar cells is reversible binding of the secretagogues to receptors located on the outer surface of the plasma membrane of the pancreatic acinar cell. Binding of the secretagogue to its receptor is both necessary and sufficient to initiate the sequence of events that ultimately causes stimulation of pancreatic enzyme secretion. Several different classes of receptors have been identified for secretagogues that act on the pancreatic acinar cells. The various secretagogues that act on the pancreatic acinar cells stimulate enzyme secretion by activating one of two functionally distinct processes. One process involves binding of the secretagogue to its receptors, mobilization of cellular calcium, and after a series of presently undefined steps, stimulation of enzyme secretion. The other process involves binding of the secretagogue to its receptors, activation of adenylate cyclase, increased cellular cyclic adenosine monophosphate (AMP), activation of cyclic AMP-dependent protein kinase, and after a series of presently undefined steps, stimulation of enzyme secretion. Secretagogues that cause mobilization of cellular calcium do not increase cyclic AMP, and secretagogues that increase cellular cyclic AMP do not cause mobilization of cellular calcium.