Effects Of The Mixture Of Methyl And Ethyl P-hydroxybenzoate On The Fertility Of Male Fruit Fly And Accumulation In Vivo

P-hydroxybenzoic acid esters also knows as enhanceparaben, mainly include methylparaben （MP）, ethylparaben （EP）, propylparaben （PP）, butylparaben （BP） and so on. Parabens belong to ester type preservative. Paranens damage cell membranes of microorganisms, denature proteins within cells, interfering with its survival and reproduction by inhibiting microbial cell respiratory enzymes and electron transfer enzyme activity. Because of its chemical stability molecular structure, low toxicity, corrosion, etc. have been widely used as a preservative in cosmetics, pharmaceuticals, foods and industrial supplies. As parabens using range promotion, its exposure levels in the environment and the kind of exposure increases, the number of bio-contact parabens exposure, contact types and sources are increasing, thus re-evaluate the safety of parabens are also increasingly important. But now, most researches focus on the toxicity of individual paraben and a little is kown for the toxicity of mixtures of parabens. Hence, It is greater realistic significance to investigate the mixed toxicity.Experiments were carried out in the wild type Drosophila melanogaster Canton-S strain, mix MP+EP （mass ratio=1:1） to three concentrations exposure groups (0.00 mg·L^-1,700 mg·L^-1 and 1000 mg·L^-1), continuously exposed the male Drosophila after eclosion. In physiological level, detection the effect on fertility, progeny development time of eggs to pupae and eggs to adult, and offspring and pupa rate of MP, EP mixture parabens on male Drosophila continuously exposed in 5 different days （9 d,18 d,27 d, 36 d and 45 d）. In the mixed parabens accumulation level, dynamic testing mixed parabens exposed different days（3 d,6 d,9 d,12 d,15 d,18 d,21 d,24 d,27 d,30 d,33 d,36 d,39 d,42 d and 45 d） in the male Drosophila testis and the residues in the content of MP and EP, and the content of MP and EP in offspring from the parental males who exposed to mix parabens in 5 different days mating with normal female Drosophila. In molecular level, the effects of MP+EP on the expression of three genes （EcR, E75 and Br） were assayed by quantitative real-time PCR after the male Drosophila were treated by mixd parabens for 9,18,27,36 and 45 days. The results show:（1） Fertility of male flies in two mix parabens exposed group (700 mg·L^-1 and 1000 mg·L^-1) were found to be significantly decreased. The development time of offspring from egg to pupa and egg to adult with the incubation time increased, the pupation rate and the emergence rate of offspring decrease, but there was no significant difference. The same exposure time, the fertility of male flies, the developmental time of offspring, the pupation rate and the emergence rate of offspring observed greater impact in the high concentration of mix parabens expose group.（2） In the control group was not detected MP and EP. The content of MP and EP in testis and residues of male flies exhibit fluctuated change tendency with time extended in the two mix parabens exposed group (700 mg·L^-1 and 1000 mg·L^-1). Parabens in male flies will be passed to offspring by mating. Offspring differences between male and female fruit flies in the content of MP and EP, and with the spawning time delayed, the content of MP and EP were decreased.（3） The quantitative real-time PCR results showed that 1000 mg·L^-1 set to raise EcR gene induced molting hormone target E75 rise, unlike Br gene expression changes, EcR and E75 gene expression trend is consistent, associated with males fertility and MP and EP content in testis. EcR and E75 gene expression trend is consistent in 700 mg·L^-1, different from the trend of Br gene expression.Integrated the experiment results showed that high concentration of mix parabens may be affected by molting hormone （20E） receptors gene expression of EcR and feedback regulation the concentration of 20E affect males sperm production, abate the male flies fertility. While the low concentration of the mixed parabens group of MP+ EP content on males produce reproductive toxicity mechanism is unclear and needs further experiments to explore, this study also provides data for safety assessment of parabens.