Effects of Genistein Isoflavone (4',5',7-Trihydroxyisoflavone) and Dexamethasone on Functional Characteristics of Spermatozoa

Caudal epididymal spermatozoa were used to study the influence of genistein isoflavone and dexamethasone (dxm) on the functional characteristics of spermatozoa. The effects of genistein alone and in combination with dxm on sperm motility, sperm morphology, spontaneous acrosome reaction (AcR), and ionophore A23187-induced AcR were investigated. The FITC-PSA/Hoechst 33258 staining procedure was used to assess sperm cell viability and AcR status and thus to differentiate between true AcR and acrosome degeneration. The overall results indicated that (1) lower doses of genistein alone, or in combination with dxm, did not significantly influence sperm motility or sperm morphology; (2) ionophore A23187 induced AcR in rat spermatozoa; (3) there appeared to be no direct correlation between sperm motility and AcR, (4) higher doses of genistein, alone or in combination with dxm, significantly interfered with percentage sperm motility and caused significant detachment of sperm heads but did not cause morphological defects; and (5) higher doses of genistein caused significant decrease in sperm acrosome reactivity with long duration of exposure. In view of the fact that sperm capacitation and AcR are physiological prerequisites for successful fertilization of oocytes, the findings suggest that chronic exposure of spermatozoa to high doses of genistein could be associated with infertility problems through suppression/inhibition of AcR and sperm motility. Dexamethasone did not appear to influence the effect of genistein on the functionality of postspermatogenic spermatozoa.