In vertebrates, chemosensitivity of nutrients occurs through the activation of taste receptors coupled with G-protein subunits, including α-transducin (G
αtran) and α-gustducin (G
αgust). This study was aimed at characterising the cells expressing G
αtran immunoreactivity throughout the mucosa of the sea bass gastrointestinal tract. G
αtran immunoreactive cells were mainly found in the stomach, and a lower number of immunopositive cells were detected in the intestine. Some G
αtran immunoreactive cells in the stomach contained G
αgust immunoreactivity. Gastric G
αtran immunoreactive cells co-expressed ghrelin, obestatin and 5-hydroxytryptamine immunoreactivity. In contrast, G
αtran 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 G
αtran and G
αgust 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.
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