Semicarbazide Exposure Induces Histological Damage and Enzymatic Reactions in Apostichopus japonicas
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Abstract:
According to the acute toxicity test, the median lethal concentration (LC50 ) of semicarbazide at 96 h was 3.72 g/L in Apostichopus japonicas (calculated as semicarbazide hydrochloride), with the 95% confidence interval as 3.43 g/L~4.02 g/L. Semicarbazide had an effect on the structure of the respiratory tree, intestines and muscles of Apostichopus japonicas. In the 1/5 LC50 group, respiratory tract lesions were severe and intestinal tissue was disintegrated with disordered smooth muscle lesions. In the 1/25 LC50 and 1/50 LC50 groups, pathological changes in respiratory, intestinal, and muscle tissues were slow but progressive and cumulative. Apostichopus japonicas was excitotoxicitory upon the exposure to the toxicity of semicarbazide, and the activities of antioxidant enzymes and key enzymes associated with neurotransmission increased first and then decreased, that is, induced first and then inhibited, with the 1/5 LC50 group exhibiting the most obvious symptom of poisoning. The 1/25 LC50 group had the highest activities of superoxide dismutase (SOD), catalase (CAT) and acetylcholinesterase (AChE), followed by the 1/5 LC50 group and 1/50 LC50 group. At the medium concentration, the maximum SOD activities of respiratory tree, intestinal and muscle for the 1/25 LC50 group were 1.78 times, 1.67 times and 2.50 times of those for the control group, respectively. The maximum CAT activities of respiratory tree, intestinal and muscle for the 1/25 LC50 group were 1.87 times, 1.96 times and 2.04 times of those for the control group, respectively. The maximum AChE activities of respiratory tree, intestinal and muscle for the 1/25 LC50 group were 7.86 times, 6.24 times and 2.86 times of those for the control group, respectively. In the end, all the enzymatic activities tended to reach the levels similar to those of the control group, which might be related to the immunity and fatigue of Apostichopus japonicas.