HISTOLOGY AND HISTOPATHOLOGY

Cellular and Molecular Biology

 

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

S. Desantis1, M. Albrizio2, G. Ventriglia1, M. Deflorio1, A.C. Guaricci2, R. Minoia2 and G. De Metrio1

1Department of Animal Health and Well-being and 2Department of Animal Production, Faculty of Veterinary Medicine, University of Bari, Italy.

Offprint requests to: Professor Salvatore Desantis, Department of Animal Health and Well-being, Faculty of Veterinary Medicine, University of Bari, S.P. per Casamassima Km. 3, I-70010 Valenzano (BA), Italy. e-mail: s.desantis@veterinaria.uniba.it


Summary. 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. Histol Histopathol 23, 555-564 (2008)

Key words: µ-opioid receptor, Glycosylation, Oviduct, Mare

DOI: 10.14670/HH-23.555