Enteroendocrine profile of alpha-transducin immunoreactive cells in the gastrointestinal tract of the European sea bass (Dicentrarchus labrax)

In vertebrates, chemosensitivity of nutrients occurs through activation of taste receptors coupled with G protein subunits, including α-transducin (Gαtran) and α-gustducin (Gαgust). This study was aimed at characterizing 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.

In vertebrates, chemosensitivity of nutrients occurs through the activation of taste receptors coupled with G-protein subunits, including alpha-transducin (G(alpha tran)) and alpha-gustducin (G(alpha gust)). This study was aimed at characterising the cells expressing G(alpha tran) immunoreactivity throughout the mucosa of the sea bass gastrointestinal tract. G(alpha tran) immunoreactive cells were mainly found in the stomach, and a lower number of immunopositive cells were detected in the intestine. Some G(alpha tran) immunoreactive cells in the stomach contained G(alpha gust) immunoreactivity. Gastric G(alpha tran) immunoreactive cells co-expressed ghrelin, obestatin and 5-hydroxytryptamine immunoreactivity. In contrast, G(alpha tran) 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(alpha tran) and G(alpha gust) antisera was determined by Western blot analysis, which identified two bands at the theoretical molecular weight of similar to 45 and similar to 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.