Mn2+: A potent antioxidant and stimulator of sperm capacitation and acrosome reaction in crossbred cattle bulls

Abstract. Manganese is a well known antioxidant and is a potent inhibitor of in vitro oxidative stress. The aim of this work was to study the influence of Mn²⁺ (60 μM) on capacitation and acrosome reaction of crossbred cattle bull spermatozoa. Fresh semen was centrifuged and pellet so obtained was suspended in TALP medium (pH 7.4). The sperm suspension was divided into four equal fractions(four tubes). In the control tube, only TALP was added; whereas the remaining three tubes were supplemented with ferrous ascorbate (FeAA – 150 μM FeSO₄ : 750 μM ascorbic acid) , 60 μM Mn²⁺ and FeAA+ Mn²⁺, respectively. All fractions were incubated incubated (37 °C) for 6 hr in CO₂ incubator. These fractions were assessed for morphology, % hyperactivity, lipid peroxidation (LPO) and % acrosome reaction. Morphology of the capacitated spermatozoa remained unaltered with FeAA/Mn²⁺/FeAA+Mn²⁺ treatments. FeAA treatment non-significantly (p ≥ 0.05) decreased % sperm hyperactivity % acrosome reaction, but, increased the LPO level. Supplementation of Mn²⁺ increased % hyperactivity and % acrosome reaction significantly (p ≤ 0.05) in FeAA untreated fractions, but, non-significantly (p ≥ 0.05) in FeAA treated fractions. Malondialdehyde (MDA – end product of LPO) decreased significantly (p ≤ 0.05) with the Mn²⁺ supplementation both in FeAA treated and untreated fractions. It is concluded that Mn²⁺ protects the bull sperm against LPO/oxidative stress and facilitates the occurrence of capacitation and acrosome reaction.