Epididymal maturation and the acrosome reaction in mouse sperm: response to zona pellucida develops coincident with modification of M42 antigen.

Development of the sperm's capacity to interact with the zona pellucida was investigated at the stage when the acrosome reaction (AR) is induced. The response of epididymal sperm to agents that affect the occurrence of the AR was used to monitor maturational changes. Despite the finding that sperm from the three main epididymal regions were competent to undergo ARs induced by the divalent cation ionophore A23187 (56% AR, 74% AR, and 83% AR in caput, corpus, and cauda, respectively), the cells' responses to solubilized zonae pellucidae were different. When challenged with 5 zonae equivalents/microliter, both corpus and cauda sperm shed their acrosomes in high numbers (75% AR and 86% AR, respectively), whereas caput sperm did not (23% AR). Previous work has shown that the presence of M42 monoclonal antibody (mAb) during in vitro and in vivo fertilization inhibits sperm penetration through the zona pellucida by specific interference with zonae pellucidae-induced ARs. In this study, presence of the M42 mAb did not affect the incidence of A23187-induced ARs, whereas the zona-induced ARs that occurred in both corpus and cauda sperm were inhibited fully with M42 immunoglobulin (Ig) G. In addition, the antigen recognized by M42 mAb on sperm, termed M42 Ag, was examined during epididymal maturation. Although antigen localization appeared indistinguishable by immunofluorescence on sperm taken from the caput, corpus, and cauda regions of the epididymis, modification of this antigen during epididymal transit was detected. Equilibrium-binding studies using 125I-M42 IgG demonstrated a progressive increase during epididymal transit in the amount of M42 mAb that bound to fixed cells. Corpus and cauda sperm bound 185% and 240%, respectively, of the 125I-M42 IgG detected on caput sperm. These changes in expression of M42 Ag paralleled a structural change: the Mr of the antigen decreased from a 195,000/210,000 doublet in caput sperm to a 185,000/200,000 doublet in corpus and cauda sperm, as determined by immunoblot analysis of sodium dodecyl sulfate (SDS)-extracted sperm. Results presented here demonstrate that mouse sperm develop the capacity to undergo a zona-induced AR during epididymal maturation. The M42 antigen, which is involved in the zona-induced AR, is modified during epididymal transit coincident with development of the sperm's responsiveness to zonae. Our working hypothesis, based on these results, is that development of the sperm's capacity to undergo a physiological AR is related to modification of M42 Ag.

Nature of the rabbit acrosome reaction-inducing activity of follicular fluid.

Follicular fluid samples from rabbits, cats, pigs, women and cows had acrosome reaction-inducing activity (ARIA) on rabbit spermatozoa as determined by differential staining after incubation with these fluids. Activity was retained after dialysis and at least 50% was found to be labile when heated to 56 degrees C for as little as 20 min. The induction of the acrosome reaction by bovine follicular fluid showed a dependence on the concentration of follicular fluid and spermatozoa and on calcium ions, and had a pH optimum of approximately 8. Enzyme treatments showed that proteases destroyed the ARIA and this activity was completely blocked by treatment of bovine follicular fluid with goat anti-bovine antiserum. Electron microscope observations indicated the similarity of the reactions observed to that occurring in vivo. It is concluded that the rabbit acrosome reaction inducing-activity of bovine follicular fluid is a serum component(s), probably a protein(s) of high molecular weight.

Immunological components of rabbit fallopian tube fluid.

PIP: The specific immunological components in the Fallopian tube fluid of the rabbit were measured and compared with circulating levels of immunoglobulins. The effect of immunoglobulins entering the oviduct on a specific enzymatic activity are also determined. Immunoglobulins were quantitated by the single radial diffusion method. In the Fallopian tube immunoglobulins were 4, 24, and 2% of serum levels of IgG, IgA, and IgM, respectively. The ratio of IgA to IgG was 1.38 while that of serum was .25, suggesting possible local secretory response in the Fallopian tube. Total immunoglobulin concentration of Fallopian tube fluid was 10% that of serum. Rabbits immunized against yeast alcohol dehydrogenase were shown to have serum and tubal fluid which inhibited enzyme activity. Tubal fluid had 4% of the activity of serum. C (3) component of serum complement was at a level in the tube which was 17% of serum. Total immunologic complement activity of tubal fluid was lacking in the first 5 days of pseudopregnancy. It is concluded that some of immunological components of complement fail to penetrate the Fallopian tube lumen.^ieng