Characterization of muscarinic acetylcholine receptors on the rat pancreatic gastrin-producing cell line B6 RIN.

ABSTRACT

The mechanisms of cholinergic stimulation of gastrin cells were studied in the rat pancreatic cell line B6 RIN. Carbachol induced an increase in intracellular Ca2+ and stimulated gastrin release in a dose-dependent manner over the range 10(-5)-10(-3) M. These effects were completely abolished by atropine, suggesting the implication of muscarinic cholinergic receptors. The binding properties of these receptors were investigated. [N-Methyl-3H]scopolamine [( 3H]NMS) binding on cell homogenates was time-dependent, saturable and consistent with a single high-affinity binding class (Kd = 39.5 pM, and Bmax = 7.9 fmol/mg DNA). Carbachol competitively inhibited [3H]NMS binding. The potency of inhibition of [3H]NMS binding by subtype selective antagonists was hexahydrodifenidol greater than pirenzepine greater than AF-DX 116. These results suggest the M3 muscarinic receptors may be involved in the carbachol-induced gastrin release from B6 RIN cells.