Inhibitory effect of thyrotropin-releasing hormone on enzyme secretion from isolated rat pancreatic acinar cells

This study reports a direct effect of TRH on amylase secretion from isolated rat exocrine pancreatic acinar cells. TRH inhibited carbachol (10(-5) M)-stimulated amylase secretion by a maximum of 24% at a concentration of 10(-11) M (p < 0.05), but did not affect basal amylase release in concentrations from 10(-13) M to 10(-8) M. Ceruletide (3 x 10(-10) M)-stimulated amylase secretion was maximally reduced by 23% at a TRH concentration of 10(-10) M (p < 0.05). Direct stimulation of protein kinase C-mediated secretion by the diacylglycerol analogue 1-oleoyl-2-acetyl-sn-glycerol (OAG) was not altered by TRH. The TRH metabolite cyclo (His-Pro) did not influence basal or stimulated pancreatic secretion in vitro. These findings point to a TRH-mediated modulation of exocrine pancreatic secretion at the receptor site.