The presence of the mu-opioid receptor in the isthmus of mare oviduct.
The presence of the mu-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 (beta-elimination) treatments. Immunoblotting analysis showed that the mu-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 mu-opioid receptor expressed in mare isthmus oviduct contains some modifications of the Galbeta(1-3)GalNAc core binding to serine or threonine. Immunohistochemistry revealed the mu-opioid receptor in the mucosal epithelium, some stromal cells, muscle cells and blood vessels. In ciliated cells the mu-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 beta-elimination. Most non-ciliated cells expressed the mu-opioid receptor with both N- and O-linked oligosaccharides, as revealed by the abolition of immunostaining after N-glycosidase F and beta-elimination. Stromal cells, endothelial and muscle cells of blood vessels expressed the mu-opioid receptor containing both N- and O-linked oligosaccharides. Myosalpinx myocytes expressed the mu-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 mu-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.
Desantis
S
S
Department of Animal Health and Well-being, Faculty of Veterinary Medicine, University of Bari, Italy. s.desantis@veterinaria.uniba.it
Albrizio
M
M
Ventriglia
G
G
Deflorio
M
M
Guaricci
A C
AC
Minoia
R
R
De Metrio
G
G
D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D004971:Estrus / Q000502:physiology; D005187:Fallopian Tubes / Q000378:metabolism*; D005260:Female; D019085:Fluorescent Antibody Technique, Direct; D006031:Glycosylation; D006736:Horses / Q000502:physiology*; D007124:Immunoenzyme Techniques; D017450:Receptors, Opioid, mu / Q000378:metabolism*
D015415:Biomarkers; D017450:Receptors, Opioid, mu