Enteroendocrine profile of α-transducin immunoreactive cells in the gastrointestinal tract of the European sea bass (Dicentrarchus labrax)
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In vertebrates, chemosensitivity of nutrients occurs through the activation of taste receptors coupled with G-protein subunits, including α-transducin (Gαtran) and α-gustducin (Gαgust). This study was aimed at characterising the cells expressing Gαtran immunoreactivity throughout the mucosa of the sea bass gastrointestinal tract. Gαtran immunoreactive cells were mainly found in the stomach, and a lower number of immunopositive cells were detected in the intestine. Some Gαtran immunoreactive cells in the stomach contained Gαgust immunoreactivity. Gastric Gαtran immunoreactive cells co-expressed ghrelin, obestatin and 5-hydroxytryptamine immunoreactivity. In contrast, Gαtran immunopositive cells did not contain somatostatin, gastrin/cholecystokinin, glucagon-like peptide-1, substance P or calcitonin gene-related peptide immunoreactivity in any investigated segments of the sea bass gastrointestinal tract. Specificity of Gαtran and Gαgust antisera was determined by Western blot analysis, which identified two bands at the theoretical molecular weight of ~45 and ~40 kDa, respectively, in sea bass gut tissue as well as in positive tissue, and by immunoblocking with the respective peptide, which prevented immunostaining. The results of the present study provide a molecular and morphological basis for a role of taste-related molecules in chemosensing in the sea bass gastrointestinal tract.
KeywordsChemosensory system Gut peptides Taste receptors Teleost
This work was partially supported by the grants PRIN/COFIN from the Italian Ministry of University, Research and Education 2008 and 2010 (to R. De G.), and R.F.O. funds from the University of Bologna (R. De G., R.C. and P.C.). R. De G. is the recipient of research grants from Fondazione Del Monte di Bologna e Ravenna. C.S. is supported by the National Institutes of Health DK41301 (Morphology and Cell Imaging Core) and University of California Los Angeles (UCLA) Academic Senate Grant.
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