Effects of zinc chloride on boar sperm quality during liquid storage at 17°C

Abstract

Objectives: The aim of this study was to evaluate the effects of zinc chloride (ZnCl2) at 20, 50, 100, and 200 μg/mL on the quality of seminal plasma-free boar sperm stored at 17°C for 7 days and to explore the underlying mechanisms. Methods: Boar sperm were collected and incubated in non-capacitation/capacitation medium to analyze sperm quality. Results: In the non-capacitated state, the addition of ZnCl2 at 20 and 50 μg/mL improved the survival rate and plasma membrane integrity of boar sperm (p < 0.05). Compared to the control group, the addition of ZnCl2 significantly increased total antioxidative capacity and CuZn superoxide dismutase activity, while reducing the malondialdehyde content (p < 0.05). ZnCl2 at 100 and 200 μg/mL significantly decreased sperm motility, protein kinase A (PKA) substrate phosphorylation, and tyrosine phosphorylation. These proteins were mainly located on the mid-pieces of the flagellum. The addition of ZnCl2 at 20 and 50 μg/mL conveyed a protective effect to boar sperm stored at 17°C. Furthermore, ZnCl2 at 100 and 200 μg/mL inhibited sperm motility via tyrosine phosphorylation, thus preventing the ‘capacitation-like’ state. In the capacitated state, there was no change in PKA substrate phosphorylation and tyrosine phosphorylation of the mid-pieces of the flagellum compared to the control groups, indicating that the addition of Zn2+ did not negatively affect capacitation of preserved sperm. Conclusions: ZnCl2 showed protective capacity to the preservation extender used for boar sperm during the process of 17°C storage, and the optimal concentration of ZnCl2 for the preservation extender was 100 μg/mL.