Stimulus–secretion coupling in exocrine pancreas: possible role of calmodulin

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Abstract
Many calcium-mediated effects in mammalian cells may be activated by calcium-calmodulin stimulated enzymes. These effects are inhibited by various antidepressant drugs which bind to and inactivate calmodulin. In the current study, calmodulin was identified by affinity chromatography and gel electrophoresis in the cytoplasm of dispersed rat pancreatic acinar cells. Its role in enzyme secretion was assessed by evaluating the effects of various antidepressant drugs on the enzyme secretory process. Chlorpromazine, trifluoperazine, thioridazine, chlorprothixene and amitriptyline inhibited amylase secretion stimulated by carbacol, A-23187, and cholecystokinin-pancreozymin but not that elicitied by dibutyryl cyclic AMP secretin or vasoactive intestinal peptide (VIP). Haloperidol, sulpiride, phenobarbital, and ethanol were without effect on secretagogue-stimulated enzyme release. Only those agents which blocked secretion also inhibited 45Ca release stimulated by carbachol from isotope preloaded cells. The data suggest that calmodulin may have a functional role in pancreatic enzyme secretion.