Acute toxicity of manganese and its role in regulating testicular enzyme activity of male rats at different time points

Abstract Background: In order to provide scientific basis for toxicity evaluation and prevention of manganese, this study aims to investigate acute toxicity and testicular alkaline phosphatase (ALP), acid phosphatase (ACP), lactic dehydrogenase (LDH) in male rats after manganese exposure at different time points. Methods: Under strict control of light/darkness (12 h:12 h), the experimental animals were injected intraperitoneally with MnCl2·4H2O at different zeitgeber time (ZT) after adaptive feeding for 7 days. The acute toxicity test was performed by Kunming mice treated with manganese once and observed for 14 days. LD50 was calculated by improved Karber method according to the death of animals in each group. Short-term repeated manganese exposure was conducted by continuous 30 mg/kg manganese exposure once a day for 21 days. And then the adult SD male rats were killed to detect activities of testicular ALP, ACP and LDH by ELISA at different ZT points the second day after exposure. Results: Acute toxic reactions of mice exposed to manganese were varied at different ZT points. The LD50 at ZT2, ZT8, ZT14 and ZT20 were 472.0 mg/kg, 408.2 mg/kg, 303.3 mg/kg and 358.0 mg/kg, respectively. Furthermore, short-term repeated manganese exposure could induce the activity changes of ACP, ALP and LDH in testes at different ZT points. ALP increased at ZT20 while decreased at other time points (P<0.05). ACP only decreased at ZT2 (P<0.05). LDH increased at ZT2 and ZT8 (P<0.05), but decreased at ZT14 and ZT20 (P<0.05). In addition, all the testicular enzymes except ACP had interactions between manganese and exposure time. Conclusion: The acute toxicity and function injury of male reproductive caused by manganese exposure are varied at different ZT points. The timing of toxic reaction needs to be considered in the toxicity evaluation of manganese.