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Fig. 1. Lectin induction of sperm tyrosine phosphorylation. (A) Purified human spermatozoa were incubated with a panel of sperm-binding lectins (Table 1; 0.5 µg/ml) for 30 minutes. Of these lectins, WGA alone demonstrated the ability to consistently up-regulate tyrosine phosphorylation. To examine the specificity of this response, spermatozoa were incubated in a cocktail of the lectins sWGA, MAA and SNA (which collectively possess the same sugar specificity as WGA) either in their native form or as cross-linked complexes (*). (B) The specificity of the WGA response was further examined by pre-incubation of sperm with either neuraminidase and/or N-acteylglucosaminidase (250 mU/ml) prior to the addition of WGA. Control treatments incorporated spermatozoa incubated in BWW prepared without HCO₃^– (–ve), or in BWW supplemented with dbcAMP and pentoxyfiline (+ve). Following immunodetection of phosphotyrosine residues (anti-py), membranes were stripped and re-probed with anti--tubulin to ensure equivalent protein loading across all treatments. The experiment was replicated three times with pooled semen samples obtained from at least three different donors, and representative blots are depicted.

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