Co-localization of Trk neurotrophin receptors and regulatory peptides in the endocrine cells of the teleostean stomach

Abstract

Recently it has been observed that a subpopulation of gut endocrine cells in vertebrates express Trk-like proteins, suggesting that neurotrophins could regulate the synthesis and storage of amines and peptides of these cells. Nevertheless, the peptides and amines present in the endocrine cells that express Trks have not been characterized. In this study we used immunohistochemistry to investigate the occurrence of Trk-like proteins (TrkA-like, TrkB-like and TrkC-like) and the possible co-localization of these with peptides and/or biogenic amines in the endocrine cells of the stomach of three teleost (bass, gilt-head and scorpionfish). No TrkA-like immunoreactivity (IR) was detected in the stomach of these species, whereas TrkB-like IR and TrkC-like IR were observed in numerous cells of the gastric epithelium. TrkB-like immunoreactive cells were present in all three species examined, and were particularly abundant in the blind sac. Conversely, TrkC-like immunoreactive cells were found only in the bass stomach, apparently co-localized with TrkB-like IR. TrkB-like IR was found co-localized with somatostatin IR in scorpionfish, and with somatostatin and CGRP IR in gilt-head and bass. Gastric endocrine cells expressing 5-HT, glucagon, insulin, met-, leu-enkephalin, substance P, PYY, VIP, CCK, NPY, bombesin and motilin were unreactive for Trk-like proteins. The present results provide direct evidence for the occurrence of Trk-like neurotrophin receptor proteins in a subpopulation of the teleostean gastric endocrine cells and suggest that neurotrophins could regulate, as in neurons, the expression of some neuropeptides such as somatostatin and CGRP. Anat Rec 256: [219][220][221][222][223][224][225][226] 1999.

TrkA and TrkC neurotrophin receptor-like proteins in the lizard gut

“…In the gut, Trk receptor proteins and mRNA have been found in the enteric nervous system (ENS; Lamballe et al 1991Lamballe et al , 1994Sternini et al 1996;Esteban et al 1998) and in endocrine cells (Esteban et al 1995(Esteban et al , 1998Shibayama and Koizumi 1996) of many species of mammals. Similar findings have been observed in birds (Hannestad et al 1998) and fishes (de Girolamo et al 1999;Lucini et al 1999a;Hannestad et al 2000). These observations in various vertebrate species argue for the preserved evolution of Trk-like molecules not only in the nervous system, but also in gastrointestinal endocrine cells.…”

“…Because these two peptides are generally employed as endocrine markers (O'Connor et al 1983;Buffa et al 1988;Cetin 1992), we can assume that the TrkA-like positive cells in lizard gut are endocrine cells. Because cells displaying chromogranins in reptiles appear to contain serotonin, histamine, peptide tyrosine tyrosine, substance P and/or somatostatin (D'Este et al 1993;Trandaburu et al 1999), it can be hypothesised that lizard TrkA-like immunoreactive cells contain one or more of these substances, as we have recently observed in some teleosts (de Girolamo et al 1999). TrkA-like immunoreactivity has been found in endocrine cells of mammals (Esteban et al 1995(Esteban et al , 1998Shibayama and Koizumi 1996), birds (Ciriaco et al 1997;Hannestad et al 1998) and fishes (de Girolamo et al 1999;Lucini et al 1999a).…”

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

“…Specificity of the 5-HT, CGRP and SOM antibodies was previously demonstrated in the sea bass by preadsorption test (De Girolamo et al 1999; Visus et al, 1996). The staining we obtained with the monoclonal SP antibody was completely overlapping with the immunostaining reported by Pederzoli et al (2004) in the sea bass with a rabbit SP antibody (Cambridge Research Biochemical, U.K.), the specificity of which was verified by immunoblocking.…”

Immunohistochemical localization of BDNF‐, TrkB‐ and TrkA‐like proteins in the teleost lateral line system

“…However, the tissue distribution of neurotrophins and/or Trk receptors in vertebrates other than mammals and birds is poorly known. Recently, Trk‐like proteins have been detected in neuronal and non‐neuronal cells of fish and reptiles, but attention was not focused on the LLS (De Girolamo et al. 1999, 2000; Lucini et al.…”

“…1995, 1998; Hallbook, 1999; Heinrich & Lum, 2000). Moreover, using Western blot analysis in teleosts, these antibodies recognize proteins whose estimated molecular masses are equivalent to those of the mammalian full‐length Trks (De Girolamo et al. 1999, 2000; Lucini et al.…”