Effects of ammonium sulfate and ammonium nitrate on spermatogenic dysfunction in rats

Background In recent years, the pollution of fine particulate matters (PM_2.5) has become increasingly serious. Its components are complex and have a variety of cytotoxic effects, including reproductive toxicity. Secondary inorganic water-soluble ions (SNA), such as SO₄^2-, NO₃^- and NH₄⁺, are important water-soluble components of PM_2.5. It is significant to study the potential reproductive toxicity of SNA.

Objective This experiment investigates the damage of ammonium sulfate and ammonium nitrate to spermatogenic function and their doses inducing spermatogenic dysfunction in rats.

Methods Ninety-six healthy male SD rats aged 3 months were randomly divided into a blank control group and low, medium, and high dose exposure groups, with 24 rats in each group. Combined ammonium sulfate (147.5, 295.0, and 442.5 mg·kg^-1, in body weight, respectively) and ammonium nitrate (178.5, 357.5, and 536.5mg·kg^-1, in body weight, respectively) at designed doses were intratracheally instilled into the trachea of rats in the three exposure groups, and sterile normal saline at the same volume for the blank control group. The exposure lasted for six weeks. At week 2, 4, and 6, the general conditions of eight random rats in each group were observed; bilateral testis and epididymis were taken to calculate organ coefficients, observe pathological changes, and detect semen quality; and serum was collected to detect sex hormone levels.

Results Compared with the blank control group, the rats in the medium and high dose exposure groups showed changes such as lying curled up and quiet, being more irritable, and lower weight after 2 weeks of exposurethe weights of the blank control group and the medium and high dose groups were (316.50±12.15) g, (300.25±9.76) g, and (287.24±14.53) g, respectively. The results of testicular tissues with HE staining showed that after 4 weeks of exposure, in the medium and high dose exposure groups, the spermatogenic tubules were structurally damaged, sertoli cells and sperms in the tubules were missing, and the morphology and structure of the tubules were abnormal, compared with the blank control group; such pathological changes were aggravated with the extension of exposure time, and the pathological changes of testicular tissues were more obvious in the high dose exposure group than in the medium dose exposure group. After 4 weeks of exposure, the sperm motility of rats in the high dose group(44.75±1.89)% was lower than that in the blank control group(53.81±4.07)%(P < 0.05). After 6 weeks of exposure, the testicular organ coefficients of the medium and high dose groups were (4.67±0.34)‰ and (3.97±0.29)‰, respectively; the sperm counts were (52.63±4.75)×10⁶ mL^-1 and (48.63±2.24)×10⁶ mL^-1, respectively; the sperm motilities were (37.81±2.88)% and (32.25±1.99)%, respectively; the above indices were reduced compared with the blank control group(5.61±0.34)‰, (73.38±6.98)×10⁶ mL^-1, and (52.56±2.99)% (P < 0.05). After 6 weeks of exposure, the levels of follicle stimulating hormone (FSH) in the medium and high dose groups(11.32±0.69) IU·L^-1 and (12.29±0.68) IU·L^-1 respectively were higher than that in the blank control group(9.23±0.74) IU·L^-1 (P < 0.05); the testosterone (T) level in the high dose group(0.69±0.08) μg·L^-1 was lower than that in the blank control group(1.45±0.24) μg·L^-1 (P < 0.05). After 6 weeks of exposure, the sperm count and motility were significantly lower than those after 2 or 4 weeks (P < 0.05). With the increase of exposure time, the T levels in the high dose groups decreased.

Conclusion Ammonium sulfate and ammonium nitrate can damage the spermatogenic function of male rats. Endotracheal intubation infusion of 295.0mg·kg^-1 ammonium sulfate and 357.5mg·kg^-1 ammonium nitrate for 6 weeks can induce spermatogenic dysfunction in rats.