Regulation of glucagon-like peptide-1 synthesis and secretion in the GLUTag enteroendocrine cell line. Endocrinology 139

Glucagon-like peptide-1 (GLP-1) released from the intestine is a potent stimulator of glucose-dependent insulin secretion. To elucidate the factors regulating GLP-1 secretion, we have studied the enteroen-docrine GLUTag cell line. GLP-1 secretion was stimulated in a dose-dependent fashion by activation of protein kinase A or C with fors-kolin or phorbol 12,13-dibutyrate, respectively (by 2.3 6 0.5-fold at 100 mM and 4.3 6 0.6-fold at 0.3 mM, respectively; P, 0.01–0.001). Of the regulatory peptides tested, only glucose-dependent insulinotropic peptide stimulated the release of GLP-1 (by 2.3 6 0.2-fold at 0.1 mM; P, 0.001); glucagon was without effect, and paradoxically, the in-hibitory neuropeptide somatostatin-14 increased secretion slightly (by 1.6 6 0.3-fold at 0.01 mM; P, 0.05). In tests of several neuro-transmitters, only the cholinergic agonists carbachol and bethanechol stimulated peptide secretion in a dose-dependent fashion (by 2.3