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Mannose-binding molecules of rat spermatozoa and sperm–egg interaction

Published online by Cambridge University Press:  01 November 1999

Hiromi Yoshida-komiya
Affiliation:
Department of Immunology & Parasitology, Yamagata University School of Medicine, Yamagata City 990-9585, Japan Department of Cell Biology, Baylor College of Medicine, Houston, TX 77030, USA.
Daulat Ram P. Tulsiani
Affiliation:
Center for Reproductive Biology Research, Department of Obstetrics & Gynecology, Vanderbilt University School of Medicine, Nashville, TN 37232-2633, USA
Toshio Hirayama
Affiliation:
Department of Obstetrics & Gynecology, Yamagata Prefectural Central Hospital, Yamagata City 990-9585, Japan
Yoshihiko Araki
Affiliation:
Department of Immunology & Parasitology, Yamagata University School of Medicine, Yamagata City 990-9585, Japan Center for Reproductive Biology Research, Department of Obstetrics & Gynecology, Vanderbilt University School of Medicine, Nashville, TN 37232-2633, USA

Abstract

We have previously reported the occurrence and partial characterisation of an α-D-mannosidase activity on plasma membranes of rat, mouse, hamster and human spermatozoa. A soluble isoform of the rat sperm surface mannosidase was purified and polyclonal antibody raised. Since several reports have suggested that mannosyl residues on the rat, mouse and human zona pellucida may be involved in sperm-zona binding, studies were undertaken to examine the receptor-like role of mannose-binding molecules on rat spermatozoa. Sprague-Dawley rats (25–30-days old) were superovulated and eggs collected from the oviduct were treated with 0.3% hyaluronidase to remove the cumulus cells. Spermatozoa, collected from the cauda epididymis were capacitated for 5 h at 37 °C in 5% CO2 in air. The sperm–zona binding assay was performed in the presence of increasing concentrations of several sugars as well as preimmune and immune (anti-mannosidase or anti-mannose binding protein) IgG. Data from these studies show that: (1) significantly fewer sperm bound per egg in the presence of competitive inhibitors of mannosidase; (2) among the sugars examined, D-mannose was the most potent inhibitor causing 70% reduction in the number of sperm bound per egg; (3) anti-mannosidase or anti-mannose binding protein (but not preimmune) IgG showed a dose-dependent reduction in the number of sperm bound per egg; (4) anti-mannosidase IgG (but not anti-mannose binding protein IgG) showed a dose-dependent inhibition of sperm surface mannosidase activity; (5) the competitive inhibitors of mannosidase or the immune IgG had no effect on sperm motility or the sperm acrosome reaction. These results suggest that mannose-binding molecule(s) such as α-D-mannosidase or mannose-binding protein on the spermatozoa may recognise mannosyl residues on zona pellucida, and play a receptor-like role in sperm-egg interaction in the rat.

Type
Research Article
Copyright
1999 Cambridge University Press

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