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Dose- and time-dependent effect of copper ions on the viability of bull spermatozoa in different media

The purpose of this in vitro study was to determine the effect of copper (Cu) on the motility and viability of spermatozoa in the presence of different culture media. Specifically, we examined the dose- and time-dependent effect of copper ions (Cu2+) on the motility and viability of spermatozoa during different time periods (Time 0 h, 1 h, 24 h). The percentage of motile spermatozoa and progressive motile spermatozoa was determined after exposure to concentrations of 3.9; 7.8; 15.6; 31.2; 62.5; 125; 250; 500; 1000 μM/L of Cu2+ using the Sperm VisionTM CASA (Computer Assisted Semen Analyzer) system. The cell viability was measured by the MTT (metabolic activity) assay. The initial spermatozoa motility in the presence of Cu2+ in physiological saline solution (PS) showed slight increased values at doses <31.20 μM/L of Cu2+ compared to the control group. The long-term cultivation (Time 24 h) reduced the average motility values in all experimental groups (P < 0.001) in comparison to the control group. Identical spermatozoa motility was detected for the percentage of progressive motile spermatozoa during all time periods. The culture medium containing 20 % bovine serum albumin (BSA), triladyl and 5 % glucose increased the overall percentage of spermatozoa motility after 1 h of cultivation. A concurrently maintained motility of spermatozoa at doses <62.50 μM/L of Cu2+ during the long-term in vitro cultivation confirms the protective effect of albumin. The cell viability was decreased significantly (P < 0.001) in all experimental groups with copper administration. The obtained data point out that Cu2+ at high doses is a toxic element on the spermatozoa motility, which subsequently disrupts the viability of cells. However, using a suitable culture medium containing an energy component- and protein-rich substrate, the spermatozoa motility could increase.