Changes and functions of Anti-Agglutinin in boar spermatozoa during their capacitation

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Three following experiments have been undertaken in this study ; 1. changes of sperm-bound anti-agglutinin during the capacitation, 2 : isolation of anti-agglutinin from seminal plasma and functional characterization of this protein on the regulation of sperm capacitation, and 3 : signaling cascade regulating sperm head-to-head agglutination. Significant results have been obtained in Experiments 1 and 3 and summarized here. Experiment 1 has revealed changes in anti-agglutinin bound to spermatozoa during the incubation designed to promote the capacitation in vitro. The relative amount of sperm-bound anti-agglutinin, assessed by Western blotting-densitometric analyses, was almost halved after the first 45-min incubation and then decreased gradually thereafter. Immunocytocheinical observation showed that the decrease of the sperm-bound anti-agglutinin occurred mainly on acrosomes in many spermatozoa during the incubation. These results indicate that a large portion of the anti-agglutinin … More bound to sperm acrosomes is released at an early stage of the Capacitation process in vitro. Experiment 3 has been conducted to reveal roles of bicarbonate-adenylyl cyclase (AC)-cAMP-protein kinase (PK) system in sperm head-to-head agglutination. In the samples incubated in Ca-free mKRB supplemented with 100 μM forskolin (an AC activator), significantly higher percentages of the spermatozoa were agglutinated with one another at the acrosome, as compared with control samples. Addition of dibutyryl CAMP (dbcAMP, an activator of CAMP-dependent PK : PKA), instead of forskolin, increased the percentages of head-to-head agglutinated spermatozoa in a dose-dependent manner between 1 and 1,000 μM. However, the effects of the addition of dbcAMP (1,000 μM) were attenuated by treatments with Rp-cAMPS (1,000 μM, a PKA inhibitor) or H-89 (5 μM, a PKA inhibitor). These results indicate that bicarbonate-AC-cAMP-PK system mediates a signaling pathway leading to head-to-head agglutination of spermatozoa. Less