Mercury-Induced Inhibition of Tyrosine Phosphorylation of Sperm Proteins and Altered Functional Dynamics of Buck Spermatozoa: an In Vitro Study.

Present study was undertaken on buck spermatozoa to investigate the effect of mercuric chloride on functional dynamics of buck spermatozoa. Four different concentrations (0.031, 0.125, 0.25 and 1.25 μg/mL) of mercuric chloride, which were 1/40, 1/10, 1/5 and equivalent to the LC value of HgCl, were selected for studying their effect following in vitro exposure for 15 min and 3 h. Exposure of spermatozoa to 0.031 μg/mL mercuric chloride for 3 h resulted in significant (p < 0.05) decrease in sperm motility, sperm having intact membrane, intact acrosome and high mitochondrial trans-membrane potential. However, following exposure to higher concentrations (0.25, 1.25 μg/mL), similar results were observed even after 15 min of exposure. HgCl significantly (p < 0.05) increased the levels of malondialdehyde and reactive oxygen species and significantly (p < 0.05) decreased total antioxidant capacity and superoxide dismutase activity in spermatozoa within 15 min of exposure. Mercuric chloride-treated spermatozoa did not show capacitation, rather exhibited spontaneous acrosome reaction along with significant increase in intracellular Ca and cAMP levels. Immuno-blotting of semen samples of control and 0.031 μg/mL mercury-treated groups showed low intensity bands of p55, p70, p80, p105 and p190 kDa tyrosine phosphorylation proteins while higher concentration-treated groups showed no such bands. Our findings evidently suggest that mercuric chloride even at 0.031 μg/mL adversely affected sperm functions, inhibited tyrosine phosphorylation proteins and capacitation due to oxidative stress. Spontaneous acrosome reaction (AR) in mercury-treated spermatozoa may possibly be due to increase in intracellular Ca and cAMP levels, and capacitation failure may be due to inhibition of tyrosine phosphorylation of proteins.