PRIMING EFFECTS OF XENOESTROGEN TREATMENTS ON VITELLOGENIN SYNTHESIS UNDER IN VITRO AND IN VIVO CONDITIONS IN THE MOZAMBIQUE TILAPIA

摘要

Effect of priming by 17β-estradiol (E_2) and nonyl-phenol (NP) on vitellogenin (VTG) synthesis was studied in the Mozambique tilapia, Oreochromis mossambicus. The vitellogenic response to secondary E_2 and NP stimulation was assessed by VTG production from the cultured hepa-tocytes of mature males (in vitro) and by VTG levels in the plasma of fry (in vivo). Amount of VTG in the culture medium and plasma samples was determined by enzyme-linked immunosorbent assay. VTG was induced in the blood circulations of both treatment groups when the fish were primed with low NP (2.5 mg kg~(-1)) and high NP (25 mg kg~(-1)), but was undetected in control during the experimental period. Addition of NP (10~(-4), 10~(-5) and 10~(-6) M) or E_2 (10~(-5) and 10~(-6) M) to media resulted in VTG synthesis in the hepatocytes of the low NP but not in those of the high NP and control in vitro experiment. Higher VTG induction was observed in the plasma of fry tilapia, which were immersed twice in NP solution (5 mg L~(-1)) than once. The vitellogenic response was enhanced when the fish were secondarily immersed with NP after 80 days. These results suggest that the primary exposure of estrogenic compounds boosted the response of VTG induction after secondary exposure.