| Dibutyl phthalate (DBP) is a kind of phthalate esters (PAEs) which belongs to environmental endocrine disrupting chemicals (EDCs) and is mainly used as the plasticizer and softener in plastic products. In recent years, DBP and other types of PAEs have become one of the most common global environmental pollutants with their hazards on human health being widely concerned.The present study aims at exploring the reproductive and developmental toxicity of DBP at low concentrations in zebrafish. Forty-eight pairs of adult zebrafish were randomly divide into 4 groups of 12 pairs each:blank control,0.01% acetone solvent control,1250μg/L DBP and 625μg/L DBP. After 30 days of exposure, zebrafish in each group were mated and the F1 zebrafish were raised up to 180dph in clean water. F1 Zebrafish were further mated, and the number of eggs, fertilization rate and hatching rate at 72 hours were recorded. With a view to distinguishing toxicity of DBP on each sex, a replacement mating test was conducted. Twelve F1 males in each treatment group were mated with F1 females in the control group. Similiarly, twelve F1 females in the treatment groups were mated with F1 males in the control group. Developmental indicators, such as body length and body weight, of F1 zebrafish were measured. Gonad histopathology of both male and female F1 zebrafish were performed. The expression of vitellogenin (VTG) mRNA was detected in both F0 and F1 zebrafish to find out whether DBP had an estrogen-like effect on zebrafish.Results showed that the average egg number of F1 zebrafish of 625μg/L DBP group and 1250μg/L DBP group were 114.5 and 10, respectively, which reduced significantly when comparing with control groups. Reduced body length and weight could be observed in F1 zebrafish of both DBP-treated groups. In the replacement mating test, the egg number and fertilization rate were 432±38 and 95±8% in the control group. When F1 males in DBP group were replaced by control F1 males, the egg number and fertilization rate were 394±46 and 92±6%, showing no significant difference with the control. However, when F1 females were replaced, egg numbers and fertilization rate were significantly reduced to 56±14 and 36±10%. Gonad histopathology showed that the ovary of Fl female zebrafish of 625μg/L DBP group had many mature vitellogenic stage oocytes (Voc), indicating a well-developed ovary and fair fecundity; besides, a slight increase of early perinucleolar stage oocytes (Poc) could also been observed. In F1 female zebrafish of 1250μg/L DBP group, mature Voc slightly decreased, but cortical vesicular stage oocytes (Coc) and Poc increased, indicating that ovary development may be slightly inhibited. Histopathologic examination of testis showed that the development of testes of F1 male zebrafish was inhibited significantly, manifested as the co-existence of abnormal seminiferous tubules, reduced sperm count and Leydig cell hyperplasia. It has also been found that exposure to DBP could not induce the expression of VTG mRNA in either F0 or Fl male zebrafish, indicating that DBP has no estrogen-like effect on zebrafish.The toxic effects of DBP found in the present zebrafish study are consistent with the testicular effects of DBP found in male rats, marmosets and human. Thus zebrafish could provide a suitable animal model for further study on the testicular dysgenesis syndromes (TDS). |
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