The role of calcium sensing receptors in GLP-1 and PYY secretion after acute intraduodenal administration of L-Tryptophan in rats

Objectives: The calcium-sensing receptor (CaSR), the major sensor of extracellular Ca2+, is expressed in various tissues, including the gastrointestinal tract. Although the essential ligand of CaSR is calcium, its activity can be regulated by aromatic L-amino acids. The expression of CaSR on enteroendocrine cells suggests that CaSR functions as a physiological amino acid sensor for gut hormone release. Here, we investigated the effects of L-tryptophan (L-Trp) on rat glucagon-like peptide-1 (GLP-1), peptide YY (PYY), and insulin secretion, and the role of CaSR in this mechanism in vivo.Methods: The effects of intraduodenal L-Trp on GLP-1, PYY, and insulin secretion were investigated. A CaSR antagonist, NPS 2143, was administered to determine whether CaSR plays a role in L-Trp-mediated gut hormone release. Male Wistar rats were divided into L-Trp, L-Trp+NPS 2143, and L-Trp+vehicle groups. Blood samples were collected, before and after the intraduodenal infusions, for determining plasma glucose, L-Trp, insul...