Vitamin E (Trolox) addition to Tris-egg yolk extender preserves ram spermatozoon structure and kinematics after cryopreservation

Abstract

Several studies reveal that vitamin E acts as a cellular stabilizer of unsaturated lipids against oxidative deterioration, thus maintaining structural and functional integrity at the subcellular level. The objective of this study was to evaluate Vitamin E (Trolox) addition to freezing extender for ram spermatozoa. Semen samples were diluted in Tris-yolk egg medium without antioxidant (control group) and with Trolox in different concentrations (30, 60 and 120μM). After thawing (37°C/30s), samples were subjected to analysis for plasma membrane integrity (PMi), acrosome integrity (Aci), mitochondrial membrane potential (MMP), sperm kinematics, and ultrastructural integrity. The Trolox 60 and 120μM groups showed higher percentages of iPMs (P<0.05) when compared to the control group. Differences were observed among groups in sperm kinematic indicators (progressive motility, linearity, straightness, oscillation index, straight-line velocity and average path velocity), with higher values (P<0.05) for the Trolox 60 and 120μM groups. On ultrastructural assessment, Trolox addition at the three concentrations preserved spermatozoon head plasma membranes, while for the spermatozoon tail, plasma membrane preservation at 60μM was higher (P<0.05) than the other groups. The Trolox 60 and 120μM groups presented more mitochondrial ultrastructural preservation than the other groups (P<0.05). These results indicate that Trolox addition to Tris-egg yolk at 60 and 120μM provides greater structural integrity (plasma membrane and mitochondria) and kinematics for ram spermatozoa after cryopreservation.