Abstract:

[Objective] This study was conducted to investigate the effects of sub-chronic arsenic poisoning on the expression of Caspase-9 protein in leydig cells of rats. [Method] A total of 40 healthy adult clean-grade male SD rats were randomly assigned into the following 4 groups：a control group and the low-, medium-, and high-dose arsenic exposure groups, with 10 rats in each group. The rats in the low-, medium-, and high-dose arsenic exposure groups were given sodium arsenate by drinking water at concentrations of 2.4, 12 and 60 mg/L, respectively, and those in the control group was given physiological saline. The exposure test lasted for 14 weeks. Following the exposure test, the number of peripheral white blood cells of the rats was counted; the serum levels of TNF-α and IL-1 were measured by ELISA assay; the ultrastructure of sperm was observed using transmission electron microscopy; the expression level and localization of Caspase-9 protein in leydig cells were assessed by immunohistochemical method. [Result] Compared with the control group, the serum levels of TNF-α and IL-1 as well as the number of peripheral white blood cells in the medium- and high-dose arsenic exposure groups significantly （P<0.05） increased. Under transmission electron microscopy, the sperm acrosome structure in the control group was intact, with uniform thickness and staining. In the low-dose arsenic exposure group, the sperm membrane swelled and the nuclear chromatin was uniform. In the medium-dose arsenic exposure group, the sperm acrosome and nucleus split, and the membrane swelled. In the high-dose arsenic exposure group, the sperm tail disrupted and the axial filament arrangement disordered. Immunohistochemical analysis showed that Caspase-9 protein mainly expressed in the cytoplasm of leydig cells, and the expression signal was dark brown. Compared with the control group, the expression level of Caspase-9 protein in the testicular tissue in all the arsenic exposure groups significantly （P<0.05） increased. [Conclusion] The increased expression level of Caspase-9 protein in laydig cells may be one of the mechanisms underlying chronic reproductive toxicity induced by sodium arsenite in male rats.

Key words: sub-chronic arsenic poisoning, leydig cell, ultrastructure, Caspase-9 protein, rat