| Objective:To study the reproductive toxicity and its related mechanisms of dibutyl phthalate (DBP) on puberty female rats.Methods:21-day-old Sprague Dawley (SD) female rats were randomly divided into 250mg/kg,500mg/kg and 1000mg/kg treatment groups and one control group(corn oil), the rats were administrated by gavage for 8 weeks. When observed vaginal opening, estrous cycles of rats were determined using vaginal exfoliative cytology examnation. By the end of 8 weeks' treatment of DBP blood samples were collected from femoral artery in proestrus and all animals were sacrificed,the wet weights of the uterus and ovaries were recorded and organ coefficients were calculated, respectively. The serum levels of estradiol (E2), progesterone (P), luteinizing hormone (LH), follicle stimulating hormone (FSH) were examined using radioimmunoassay. The mRNA levels of aromatase, cholesterol side-chain cleavage enzyme and peroxisome proliferator-activated receptor y of ovaries were detected by real-time fluorescent quantitative polymerase chain reaction (RT-PCR).Results:(1) The body weight (BW) among treatment and control groups was statistically different (F=3.244, P<0.01), compared with the control group, BW of 500mg/kg group was higher significantly (P<0.05), there were no significant difference of BW between 250mg/kg, 1000mg/kg group and control group (P>0.05), BW of 500mg/kg group was significantly higher than that of 1000mg/kg group (P<0.05); (2) There was no significant difference of uterus and ovary organ coefficients among treatment and control groups (P>0.05); (3) There was no significant difference of vaginal opening time among treatment and control groups (P>0.05). The difference of period of estrous cycles among treatment and control groups was statistically significant (F=25.599, P=0.001), compared with the control group, the periods of estrous cycles in 250mg/kg,500mg/kg and 1000mg/kg groups were significantly longer than that of the control group (P<0.05 or P<0.01), but there were no significant differences of estrous cycles among the three treatment groups (P>0.05). The difference of period of estrus between treatment and control groups was statistically significant (F=8.533, P=0.001), compared with the control group, the periods of estrous in 250mg/kg, 500mg/kg and 1000mg/kg groups were longer than that of the control group(P<0.05orP<0.01), but there were no significant differences of estrus among three treatment groups (P>0.05); (4) There was significant difference of serum estradiol levels among treatment and cotrol groups (F=13.502,P=0.001), compared with the control group, the levels of serum estradiol were elevated statistically in 250mg/kg,500mg/kg and 1000mg/kg does groups (P<0.05 or P<0.01), the serum estradiol levels was higher in 250mg/kg group than those of 500mg/kg and 1000mg/kg groups (P<0.05andP<0.01).There were statistically significant differences of serum progesterone levels among treatment and control groups(F=4.306, P=0.014), the serum progesterone level in 1000mg/kg does group was lower than that of the control group (P<0.05), while there was no significant difference of serum progesterone between 250mg/kg or 500mg/kg groups and the control group (P>0.05).The levels of serum LH and FSH between trestment and cotrol groups didn't change significantly(P>0.05); (5)The expression levels of P450arom mRNA in ovarian was statistically different in treatment and the control groups(H=15.895,P<0.05), compared with the control group, the expression levels of P450arom mRNA in ovarian increased in 250mg/kg,500mg/kg and 1000mg/kg does groups (P<0.01), while there were no significant differences of P450arom mRNA expression levels were observed among three treatment groups (P>0.05).The expression levels of P450scc mRNA in ovarian were significant different in treatment and the control groups(H=15.591 P<0.01), compared with the control group, the expression levels of P450scc mRNA in ovarian reduced in three treatment groups (P<0.01), but there were not significant differences in expression levels of P450scc mRNA among three treatment groups(P> 0.05); (6) The expression levels of PPARy mRNA in ovarian in 500mg/kg and 1000mg/kg does groups were significantly higher than that in the control group (P<0.05 and P<0.01), and the expression level of PPARy mRNA in 1000mg/kg does group was higher than those of 250mg/kg and 500mg/kg groups (P<0.05).Conclusion:(1) DBP has adverse effects on reproductive endocrine function of puberty female rats. The disrupting effects of DBP on reproductive endocrine functions of puberty female rats include:prolonged estrous cycle, increased the serum estradiol level and decreased serum progesterone level.(2)The possible mechanisms of female reproductive toxicity induced by DBP may be related to the increased expression of the key enzyme P450arom mRNA and the decreased expression of P450scc mRNA in ovary. The reproductive toxicity in puberty female rats of DBP may also be associated with the activating PPARy mRNA expression of granulosa cells in ovary. |
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