Abstract
Background/Aims: Recent knowledge indicates that neurotrophins play a significant role in neuroendocrine systems through their specific receptors TrkA, TrkB, TrkC and low-affinity p75<sup>NTR</sup> receptor. TrkA and TrkB receptors have been previously detected in numerous endocrine cells in human anterior pituitary and adenomas. In the present study, the localization of p75<sup>NTR</sup> and TrkC along with TrkA and TrkB receptors was investigated. Methods: Semi-serial paraffin-embedded sections of 5 human normal pituitaries and 30 adenomas were immunostained using specific antibodies. Results: Expression of p75<sup>NTR</sup> receptor was demonstrated in the intricate capillary and reticulin network in the anterior pituitary and in the pericapillary tissue and pituicytes in the posterior lobe. p75<sup>NTR</sup> immunoreactivity was absent from all adenomas. In normal anterior pituitary, a few scattered cells showed weak TrkC immunoreactivity in contrast to a high percentage of endocrine cells distributed throughout the pars distalis and pars intermedia which exhibited strong TrkA and/or intermediate TrkB immunoreactivity. Double immunohistochemistry demonstrated TrkA immunoreactivity in more than 80% of lactotropes and 70% of corticotropes and to a lesser extent in other cell types. Furthermore, in the majority of adenomas, independently of type, sex and age, a high percentage of TrkA- and/or TrkB-positive cells was detected. Interestingly, TrkC expression appeared to be increased in some adenomas compared to normal pituitary. Endothelial cells and perivascular connective tissue were always TrkB-immunostained. Conclusion: The above findings support a potential role of all neurotrophins, through their different receptors, in pituitary functions.
Published Version
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