Objective: To study the effects of 17beta-estradiol (E2) on the activation of human spermatozoa and the possible mechanism.
Methods: Spermatozoa of fertile men were stimulated by E2 and the membrane impermeable conjugated 17beta-estradiol (E2-BSA) respectively. Then the acrosme reaction (AR) rate was determined by triple-stain technique and the intracellular calcium concentration ([Ca2+]i) in spermatozoa was measured by flow cytometry. The changes of [Ca2+]i were measured again following the addition of E2 and E2-BSA in the calcium-free medium.
Results: E2 significantly increased the AR rate and the [Ca2+]i in capacitated human spermatozoa, while it had no effects on the uncapacitated spermatozoa. E2-BSA also promoted AR and increased [Ca2+]i in the capacitated human spermatozoa. Additionally, the change of [Ca2+]i was absent in case that human spermatozoa were stimulated by E2 or E2-BSA in the calcium-free medium.
Conclusion: Estrogen can activate human spermatozoa and such activation is probably mediated by the integrating of estrogen with the specific sites on human spermatozoa and thus causing the influx of extracellular calcium.