Bull Spermatozoa under Mercury Stress

Abstract

Defective sperm function is the most prevalent cause of male infertility and is difficult to treat. This study was designed to evaluate the effect of mercuric chloride (HgCl2) at 50-300 micromol/l concentration range, in vitro, on the sperm membrane and DNA integrity, viability, reduced glutathione (GSH) content and acrosomal status of the bull spermatozoa. The samples were processed for sperm analyses using semen-diluting fluid [phosphate-buffered saline (PBS), pH 7.2]. I recorded a meaningful increase in the lipid peroxidation (LPO) rate and a drastic fall in the spermatocrit values under mercury additions, dominantly at 300 microM mercury concentration, indicating a deleterious effect of mercury on the sperm membrane intactness. There was also a strong negative correlation between LPO rate and percentage of viable spermatozoa (r = -0.9, p < 0.001). GSH content was significantly impaired. Data obtained from Comet assay [single-cell gel electrophoresis (SCGE)] technique revealed that mercury is capable of inducing DNA breaks in the sperm nuclei. Interestingly, 90% of DNA breaks were double-stranded. The correlation between LPO rate and percentage of DNA breaks was found to be 0.9 (p < 0.001). Results of the gelatin test indicate that mercury is capable of altering the integrity of acrosomal membranes, showing an abnormal acrosome reaction. In this regard, a strong correlation was found between LPO rate and percentage of halos (r = -0.9, p < 0.001). In conclusion, mercury proved to be a potential oxidant in the category of 'environmental factors' to bull spermatozoa. Hence, considering the widespread use of mercury and its compounds, these metals should be regarded with more concern.