Muscarinic receptors and amylase secretion of rat pancreatic acini during cerulein-induced acute pancreatitis

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Abstract
This study examines the effects of cerulein-induced acute pancreatitis on the secretory response of rat pancreatic acini to carbamylcholine and concentration of acinar muscarinic receptors. Rats were injected subcutaneously every 8 hr with cerulein, 12 μg/kg, for two days. They were sacrificed 2 and 4 hr after the first injection, 4 hr after the second and third, and 8 hr after the sixth. By 2 hr after the first injection, carbamylcholine showed decreased potency for stimulating amylase release; decreased potency becomes maximal after the second injection. Four hours after the first injection, carbamylcholine also showed decreased efficacy for causing maximal amylase release. In the course of development of pancreatitis, progressive reductions in muscarinic receptor concentrations were evident from 4 hr after the second injection. Following the complete treatment (8 hr after the sixth injection), no alteration could be observed in the affinity or proportions of each agonist class of muscarinic receptors. These studies indicate that the pancreatic acinar cells still remain functional after acute cerulein-induced pancreatitis, although significant reductions in potency and efficacy of carbamylcholine to cause amylase release and reduced muscarinic receptor concentration occur.