The presence of the µ-opioid receptor in the isthmus of mare oviduct

• Autores: S. Desantis, G. Ventriglia, M. Deflorio, Gregorio de Metrio, M. Albrizio, A.C. Guaricci
• Localización: Histology and histopathology: cellular and molecular biology, ISSN-e 1699-5848, ISSN 0213-3911, Vol. 23, Nº. 5, 2008, págs. 555-564
• Idioma: inglés
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• Resumen

  • The presence of the µ-opioid receptor and the type of glycosylation in the third extra-cellular loop of this receptor was investigated in the isthmus of mare oviduct during oestrus by means of immunoblotting and immunohistochemistry combined with enzymatic (N-glycosidase F and O-glycosidase) and chemical (ß-elimination) treatments. Immunoblotting analysis showed that the µ-opioid receptor consists of two peptides with molecular weights of around 65 and 50 kDa. After N-deglycosylation with N-glycosidase F an additional immunoreactive peptide was observed at around 30 KDa. The cleavage of O-glycans by O-glycosidase failed in immunoblotting as well as in immunohistochemistry investigations, revealing that the third extra-cellular loop of the µ-opioid receptor expressed in mare isthmus oviduct contains some modifications of the Galß(1-3)GalNAc core binding to serine or threonine. Immunohistochemistry revealed the µ-opioid receptor in the mucosal epithelium, some stromal cells, muscle cells and blood vessels. In ciliated cells the µ-opioid receptor showed N-linked glycans, since the immunoreactivity was abolished after N-glycosidase F treatment, whereas it was preserved in the apical region after ß-elimination. Most non-ciliated cells expressed the µ-opioid receptor with both N- and O-linked oligosaccharides, as revealed by the abolition of immunostaining after N-glycosidase F and ß-elimination. Stromal cells, endothelial and muscle cells of blood vessels expressed the µ-opioid receptor containing both N- and O-linked oligosaccharides. Myosalpinx myocytes expressed the µ-opioid receptor with O-linked oligosaccharides. The immunopositive myocytes formed a circular coat in the intrinsic musculature, whereas they were arranged in some isolated, oblique bundles in the extrinsic musculature. In conclusion, the µ-opioid receptor could have a role in the production and the movement of isthmus lumen content that contributes to ensuring the effective condition of the sperm in the mare oviduct.