Fatty acids stereospecifically stimulate neurotensin release and increase [Ca2+]i in enteric endocrine cells

Abstract

In primary cultures of canine enteric endocrine cells, fatty acids directly stimulated the release of neurotensin-like immunoreactivity (NTLI). This stimulatory effect was cell specific, selective for long-chain unsaturated fatty acids, and stereospecific. Saturated fatty acids of comparable chain length and trans isomers of long-chain unsaturated fatty acids had no effect on basal NTLI secretion. NTLI release in response to oleic acid (cis-11) was dose dependent with an apparent EC50 of 37 +/- 0.18 microM. Cyclooxygenase inhibitors had no effect on fatty acid-stimulated NTLI release, indicating the response was not mediated by the production of active arachidonic acid metabolites. Somatostatin (100 nM) inhibited maximal oleic acid-stimulated NTLI release by 92%. Long-chain unsaturated fatty acids also selectively and stereospecifically stimulated an increase in the mobilization of [Ca2+]i to 313.5 +/- 28.6% of resting [Ca2+]i. Staurosporine, an inhibitor of protein kinase C, dose dependently inhibited oleic acid-stimulated NTLI release with an IC50 value of 22 +/- 0.4 nM. Long-chain unsaturated fatty acids had no effect on basal NTLI secretion from rat pheochromocytoma cells and medullary thyroid carcinoma cells, two clonal lines that express NTLI. The cell-specific, selective stereospecific, and inhibitable action of fatty acids on NTLI secretion suggests that the effect of fatty acids on enteric endocrine cells is indicative of a receptor-mediated mechanism.