NO Intervention Of Carbon Disulfide Toxicity On The Reproductive Secretion Function Of Hypothalamus -pituitary-testis Axis In Male Rats

Carbon disulfide (CS₂) is a commonly used industrial organic solvent. In recent years, reports of CS₂ on male reproductive system gradually increased both at home and abroad. Preliminary study in our laboratory showed that CS₂ can not only lead to secretion disorders of hypothalamus-pituitary-gonadal axis (HPGA) of male rats, but also lead to decrease the nitric oxide (NO) concentration in testicular tissue, total nitric oxide synthase (NOS) activities and inducible NOS (iNOS) activities. Therefore, we speculated that CS₂ may influence the secretion of NO by affecting the NOS activities in the hypothalamus, pituitary and testis, and then lead to changes in HPGA secretion, ultimately affect the male reproductive health. In this study, we took animal experiments to analyze the changes of HPGA secretion function and their mutual relations induced by CS₂ and the intervention of NO donor (sodium nitroprusside, SNP) and NOS inhibitor (N-methyl-L-arginine, L-NMMA), in order to further clarify the role of NO on reproductive endocrine system and provide a theoretical basis for the prevention and treatment of CS₂ poisoning.36 Sprague-Dawley male rats were randomly divided into 6 groups: (1) CS₂ treatment group (0,50,250 mg/m³): rats were exposed to CS₂ by inhalation for 10 weeks, 5 d/w, 2 h/d; (2) The other three groups: rats were intraperitoneal injection with NS(2.5 mg/kg),SNP (5 mg/kg) and L-NMMA (2 mg/kg) after exposure to CS₂ at a concentration of 1250 mg/m³ for 10 weeks (before the end of 10 days). After treatment, pathological changes, NOS activities, NO content, sex hormone levels and sperm quality were observed with HE staining, nitrate reductase assay, radioimmunoassay, flow cytometry and immunohistochemistry.The results were as follows: 1) iNOS and nNOS mainly expressed in Leydig cells, eNOS in Leydig cells, germ cells (mainly primary spermatocytes), vascular endothelial cells and smooth muscle cells.And sub-type NOS expressions decreased in CS₂ exposure groups and L-NMMA groups, slightly increased in SNP group. 2) NOS activities and NO content decreased in CS₂ exposure groups, SNP increased the activities of NOS and the concentration of NO in serum, hypothalamic, pituitary and testis. 3) The levels of GnRH, LH and T decreased, while FSH increased with the increasing doses of CS₂. Compared with 1250 mg/m³ CS₂ group, GnRH, LH and T levels increased significantly when rats were injected with SNP, the serum GnRH, LH and T levels were decreased, but FSH levels did not change significantly between CS₂ + L-NMMA group and 1250 mg/m³ CS₂ group. 4) Sperm counts reduced, abnormal sperm rate increased, sperm motility rate, movement ablity, sperm beat frequency decreased in CS₂ groups compared with the control group. SNP could ameliorate these results. 5) HE staining showed that in CS₂ treatment groups, hypothalamic nuclei condensation, part of the cytoplasmic vacuolation and edema of neurons, and accompanied by glial cell hyperplasia. Pituitary eosinophils increased in CS₂ exposure groups, especially in the high dose group. Part of the cells showed nuclear condensation, cytoplasmic vacuolization; Atrophic seminiferous tubule, irregularly arranged and reduced germ cells were shown in CS₂ exposure groups. SNP could decrease the effects of CS₂ on pathological changes.The above experiments clearly indicated that CS₂ can change NOS activities and NO content, serum sex hormone levels, sperm quality and damage morphological structure of tissues. Meanwhile, SNP can reduce the tissue damage and reproductive endocrine function to some extent caused by CS₂, suggesting that the effects of CS₂ on the reproductive secretion of the hypothalamus-pituitary-gonadal axis are mediated by NO. Toxic effects of CS₂ on the body can be intervented to some extent by NO.