Rat pancreatic AR42J cells. Amphicrine cells as an in vitro model to study peptide hormone receptor regulation.

The rat pancreatic acinar tumor cell line, AR42J, is widely used to study pancreatic acinar cell biology and biochemistry. In addition to the well-documented exocrine cell features, we have identified by immunofluorescence and by electron microscopy the co-expression of small neuroendocrine (NE) vesicles using the NE vesicle-specific markers synaptophysin and "protein S.V.2." AR24J cells store [3H]GABA, which is secreted upon potassium depolarization in a calcium-dependent manner. In addition, we found the expression of the receptor for the neurotransmitter substance P by using a receptor-specific cDNA probe. Glucocorticoid treatment, which profoundly inhibits cellular growth and induces differentiation, results in a rapid decrease of substance P receptor (SPR) gene expression as assessed by Northern blot analysis. Intracellular Ca2+ mobilization was then determined in response to substance P in control cells and glucocorticoid-pretreated cells by dual wavelength spectrophotometry using fura-2 in single cells. Glucocorticoid-mediated down-regulation of substance P receptors resulted in a dose- and time-dependent decrease of the intracellular Ca2+ mobilization stimulated by substance P. In summary, these data indicate that AR42J cells display an amphicrine phenotype with two differentially regulated secretory pathways; during glucocorticoid-induced differentiation, the cells become less sensitive to substance P stimulation as a consequence of reduced gene expression of the substance P receptor.