Experimental Study On The Toxicity And Mechanism Of Premature Ovarian Failure Induced By Nickel Sulfate To Female Mice

Objectives: The toxic influence and mechanism of nickel sulfate on thalamencephalon and ovary were studied in order to provide scientific evidence for preventing and curing the premature ovarian failure induced by nickel sulfate to female mice.Methods: Forty-eight healthy Kunming mice were delaminated according to their body weight and then randomly divided into 4 groups (12 in each group). The different experimental doses of nickel sulfate were determined by the approximate does of 1/16,1/8,1/4 of LD₅₀(40mg/kg) of nickel sulfate on mice, viz. normal control group(injected intraperitoneal with NS),low does nickel sulfate test group(2.5mg/kg), medial does group(5.0mg/kg) and high does group(10.0mg/kg). All groups were injected intraperitoneal continuously for 12 days. The morphological changes of thalamencephalon and ovary were observed by light microscopy; the estrus cycle were observed by vaginal smears of exfoliate cytoscopy; the cell cycle and DNA content of thalamencephalon and ovary were inspected by flow cytometry and immunohistochemical SABC assay was adopted to examine the expressions of P₅₃,P₁₆,Bcl-2 protein in ovarian tissues.Results: (1) The morphological characteristic of apoptosis was observed in ovary but there were tropic morphological characteristic of apoptosis appeared in the thalamencephalon. (2) Intraperitoneal injection with nickel sulfate to female mice could confuse estrus cycle, the times of estrus cycle of experimental groups were delayed, and the diestruses were prolonged and irregular. (3) The results of FCM on ovarian cell showed that nickel sulfate could result in the arrest of G₀/G₁ phase and the reduction of the percentage of G₂/M phase, sub-G₁ before G₁ phase in the high does group, the percentage of apoptosis ratio and DNA heteroploid index (D.I.) was also increased whereas cell proliferation index (PI) was reduced. All the changes were correlated with the exposure level. (4) The results of FCM in thalamencephalon cell showed that with the increasing of exposure does, the G₀/G₁ phase were arrested, and the percentage of G₂/M,S phase were reduced, and the PI were decreased. (5)The expression of P₅₃ and Bcl-2 protein in ovary of mice were significantly down-regulated by nickel sulfate with the increasing of exposure does compared with control group (P<0.05); the expression of P₁₆ protein in each group was significantly up-regulated by nickel sulfate compared with control group (P<0.05).Conclusion: Injected intraperitoneal with nickel sulfate could induce POF of female mice. The mechanism may have something to do with the damage of thalamencephalon-ovarian axis and reproductive system and the effect of damage related with the regulation of cell cycle and the induction of apoptosis in mice's ovarian cell. The apoptosis of mice's ovarian cell is probably related to the reduction of P₅₃,Bcl-2 protein and the increase of P₆₁ protein.