Combined Effects Of Formaldehyde And Benzene On Reproductive Toxicity In Male Mice

With the development of technique and economy, indoor ornament isbecoming prevalent increasingly. Deleterious and toxic substance pollutionhas been an important public health problem because of poor administrationin healthy requirement. Formaldehyde and benzene are the main indoorpollutants. Those people exposed by benzene showed genetic andreproductive toxicity, hyperlipemia and abnormal electrocardiogram, evennerve behavior and neurotic autonomic dysfunction. Long-term Exposureby formaldehyde would lead to carcinogenesis, malformation andmutagenesis. But there's not any report about the combined effects of thetwo substances on the reproductive toxicity now. This study is to observethe combined effects of formaldehyde and benzene on the reproductivesystem of mice.ObjectiveTo study the combined effects of formaldehyde and benzene on thereproductive genetic toxicity of male mice. Male mice reproductive cellenzyme activity in testis, lipid peroxidation, testosterone in serum, cellcycle and cell apoptosis of the testicle cell, DNA injure of the testicle cell,spermatogenesis dysfunction and pathological change were observed afterthe mice were exposed by formaldehyde and benzene. And the embryo livercell micronuclei genesis in mice were detected to observe the geneticeffects of formaldehyde and benzene.MethodsThis study was grouped according to the analytical method ofcombined effects, 2×2 factorial experiment design. There were two factors,formaldehyde and benzene. And each factor had two levels, exposure andunexposure. So there were four combination in all, ① exposed by neitherformaldehyde nor benzene, ② exposed by formaldehyde only, ③exposedby benzene only, ④ exposed by both formaldehyde and benzene. The micewere grouped into four groups according to randomization principle,negative control group , formaldehyde exposure group, benzene exposuregroup , combined exposure group and positive control group(used to detectthe teratospermia and filial generation foetus mice hepatocytemicronucleus) . Twelve male mice per group and twenty four female miceper group.Male mice positive control, formaldehyde dealing group, benzenedealing group and their combined group inhaled toxic substance silently for12 w, 2h/d, 6d/w. The mice in the negative group inhaled normal air. Theconcentration of formaldehyde and benzene that the mice inhaled were 42mg/m3 and500 mg/m3, respectively. Positive control mice were injectedwith 50mg/kg cyclophosphamide intreperitoneally for continuous 5 days.One male mouse and two unmated female mice that didn't inhale the toxicsubstance mated.Testosterone level in serum, enzyme activity of testicle cells and lipidperoxidation, the change of germ cells cycle, apoptosis percentage intesticle cells, spermatogonia DNA damage, sperms aberration andpathological examination of testis in male mice were detected after the micewere killed. Female mice were dissected after they were pregnant for 16days to detect uterus conditions. Pregnant rate, living embryo number andfetal liver cell micronuclei rate were recorded.The present experiment was designed according to 2×2 factorialdesigns model. The data were analyzed with SPSS 13.0 and the results weredemonstrated as x ± s. The ANOVA and t test were used to analyze themean, the χ2 test was used to examine the classified variables, and the 2×2factorial designs was used to estimate combined effects of two toxicsubstances.Results1. Results of testis weight in mice: There's no significant differencebetween the experimental groups and the negative control group in organindices(P >0.05).2. Results of testis cell enzyme activity in mice: Compared with thenegative control group, LDH, G-6-PD and SDH activity of testis in mice ofthe experimental groups decreased significantly(P<0.01 and P<0.05). LDHin combined group of formaldehyde and benzene decreased significantly byfactorial analysis, which showed the combined effect of formaldehyde andbenzene(P<0.05).3. Results of testis cell apoptosis and cell cycle: The testis cellapoptosis rate and the percentage of G0/G1 phase cells in all experimentalgroups significantly increased than the negative control group (P<0.01 andP<0.05). While the percentage of G2+M and S phase cells in allexperimental groups were lower than the negative control group (P<0.01and P<0.05).The result of factor analysis indicated that there was acombined effects of formaldehyde and benzene on increasing apoptosis rateof testis cells (P<0.05).4. Result of spermatogonia DNA damage of mice: The percentage ofspermatogonia DNA damage in all experimental groups were higher thanthe negative control group significantly (P<0.01).The 2×2 factorial designsanalysis indicated the combined effects of formaldehyde and benzene onthis index (P<0.05).5. Testis histopathology of mice: The results showed that seminiferoustubules were damaged in all experimental groups, matrix cells arrayedloosely and secondary spermatocyte swelled, mature germ cellsdegenerated in different extent, especially in the formaldehyde and benzenecombined group. There's even individual germ necrosis.6. Results of serum testosterone level of mice: Serum testosteronecontent in mice of experimental group were lower than the negative controlgroup significantly (P<0.01). There's a combined effects of formaldehydeand benzene on testosterone content according to factorial analysis(P<0.01).7. Results of sperm aberration rate of mice: Sperm aberration rate inall experimental groups were higher than the negative control group(P<0.01). And this indicated the combined effects of formaldehyde andbenzene on sperm aberration according to factorial analysis (P<0.01).8. Results of reproductive ability of male mice: There's no differenceof mating rate and pregnant rate in female mice between all experimentalgroups and negative control group. Fetal absorption rate in all experimentalgroups were higher than the negative group significantly (P<0.01), whileaverage alive fetus number decreased significantly (P<0.01).9. Results of the filial fetal liver cell micronucleus of male mice: Fetalliver micronucleus rates in experimental groups had a increasing trendcompared with the negative control group, but there's no obviousdifference(P >0.05).10. Results of the testis lipid peroxidation of male mice: Comparedwith the negative control group, SOD activity of testis of mice in allexperimental groups decreased significantly (P<0.01), MDA content informaldehyde exposure group and combined exposure group increasedsignificantly (P<0.05 and P<0.01). There were the combined effects offormaldehyde and benzene on increasing SOD activity (P<0.05) anddecreasing MDA content (P<0.05) according to factorial analysis.ConclusionsThe study showed that formaldehyde and benzene had the combinedeffects on decreasing the LDH activity of the testis cells in male mice,increasing the testis cells apoptosis rate, leading to spermatogonia DNAinjury and germ aberration, decreasing testosterone level in serum, leadingto oxidative damage of testis tissue, etc. In a word, formaldehyde andbenzene had combined effect on male mice reproductive genetic damage ata certain degree.