PROBLEM: To develop an immunohistochemical assay for determination of acrosome-reacted human sperm and to study the effects of progesterone and cholesterol treatment on human sperm acrosome reaction.
METHOD OF STUDY: Three distinct anti-sperm monoclonal antibodies were biotinylated and used as probes for assessment of acrosome reaction in a 30-min immunohistochemical assay. Progesterone and/or cholesterol were added to sperm preparation to influence the acrosome reaction in different experimental conditions.
RESULTS: Percentages of acrosome-intact sperm decreased significantly during the 18-hr incubation. Acrosome reaction could be induced by progesterone as early as 2 hr after sperm incubation in human tubal fluid. The degree of progesterone-induced acrosome reaction was time dependent and the optimal effect was reached by adding 10 μg/ml progesterone for 30 min incubation. Progesterone-induced acrosome reaction was shown to be hormone-concentration dependent with 50% stimulation at 1 μg/ml. Cholesterol (1 μg/ml) was found to inhibit progesterone-induced acrosome reaction either by co-incubation with human sperm during capacitation, or by simultaneous incubation with progesterone during acrosome reaction induction.
CONCLUSIONS: Assessment of human sperm acrosomal status by avidin-biotin immunohistochemical assay can be a routine in clinical laboratories for male infertility services. Cholesterol can inhibit progesterone-induced acrosome reaction, possibly by its modifications of sperm plasma membrane and/or interference of progesterone binding to its surface receptors.