N-acetylneuraminic acid and hostile mucus infertility.

A total of 39 samples of hostile mucus, as defined by postcoital examination, were examined for N-acetylneuraminic acid (NANA) deficiency, as measured by the enzymatic addition of NANA, spermatozoal penetration and immobilization. Only 56.7% of the mucus samples were deficient in NANA and this did not correlate with spermatozoal penetration or immobilization, which were negatively correlated. Thus, as the spermatozoal hostility in the mucus decreases, spermatozoal penetration increases. This finding also applies to hostile mucus not deficient in NANA. In contrast, resialylation of NANA hostile mucus, deficient and not deficient in NANA, although not enhancing spermatozoal penetration, did reduce spermatozoal immobilization. Thus, components of the mucus deficient in NANA and/or the lack of unbound NANA may contribute to mucus hostility, but it is not the only hostile factor. In addition, SEM studies of NANA-deficient mucin before and after resialylation were shown to have similar structures. Hence ultrastructural changes are not apparent in NANA-deficient mucin, and this supports the previous finding that NANA deficiency does not impede spermatozoal penetration. The spermatozoa from the husbands of the infertile couples formed three distinct groups in terms of spermatozoal penetration and immobilization in normal donor mucus. One group demonstrated normal levels of spermatozoal penetration and immobilization in donor mucus. A second group was demonstrable in which spermatozoal penetration was similar to that in the wife's hostile mucus, but had a normal level of spermatozoal immobilization. In the third group, both spermatozoal penetration and immobilization in donor mucus were similar to that in the wife's hostile mucus. The results demonstrate that not all hostile mucus is deficient in NANA, and that other unknown factors are involved. In addition, there are also male factors which may impede spermatozoal penetration and/or result in the inability of the spermatozoa to survive in normal donor mucus.