Dispersed rat parotid acinar cells. III. Characterization of cholinergic receptors.

The in vitro characterization of cholinergic receptors in dispersed rat parotid acinar cells was accomplished through investigations of the net transmembrane fluxes of K in response to exposure of the cells to selected cholinergic agonists and antagonists. Interaction of acetylcholine bromide (ACh) and carbamylcholine (carbachol) with the cholinergic receptors resulted in rapid net efflux of K from the cells. This cellular response was demonstrable in concentrations of carbachol as low as 10(-8) M. With gradual increase in the concentrations of the agonist an increase in the K efflux was observed up to 10(-5) M. At higher concentrations of this cholinergic agonist no further increases in the net K efflux were observed. The response of the cells to cholinergic agonists was inhibited by atropine but not by the adrenergic antagonists phentolamine or propranolol, suggesting cholinergic agonist-antagonist interactions at the receptor site. The dispersed rat parotid acinar cells appear to have functionally intact cholinergic receptors and could be used as valuable experimental tools for the study of receptor physiology and pharmacology as well as of other aspects of secretory function at the cellular level.