PM10 Mechanisms of Toxic Action
Exhibit Hall
8:00 AM - Monday
(PM154) Effect of waterborne B[a]P exposure on gene expression of steroidogenic enzymes and reproduction in zebrafish.
Hoffmann, J1, Oris, J1, 1 Miami University, Oxford, OH, USA
ABSTRACT- The objectives of this study were to 1) determine if waterborne exposure to the model PAH, benzo[a]pyrene (B[a]P), affected reproduction in zebrafish and 2) determine if gene expression of the steroidogenic enzymes, P450scc, P450c17, P450arom, and 20
-HSD was affected. Three month old male and female zebrafish (total n=100) were exposed to nominal concentrations of 0, 1.5, and 3.0 
g/L B[a]P in 75 L tanks for 61 days. Egg production in each tank was monitored on days 31-48. On day 49, male and female fish were separated prior to pair-wise breeding trials. Exposed females were paired with unexposed males and exposed males were paired with unexposed females. Livers and three stages of oocytes from 8 females per concentration were frozen at -80 C on days 53-56 and testes were weighed and frozen on day 61 for gene expression analysis using reverse transcription, real-time PCR. A 50% and 48% reduction in total egg output during days 31-48 was observed in the 1.5 and 3.0 g/L treatments as compared to controls, respectively. In pair-wise breeding trials, spawning was significantly reduced in female fish exposed to 3.0 g/L B[a]P while no effect on egg number or percent spawning was observed in pairs with exposed males. A significant increase in 20-HSD mRNA occurred in fish exposed to 1.5 and 3.0 g/L as compared to the controls. There was a 45% reduction in P450arom expression in 3 g/L B[a]P compared to controls. No significant difference existed in the expression of 20-HSD, P450c17, and P450arom in testes. The results from this study demonstrate that reproduction in zebrafish is affected by waterborne exposure to B[a]P and that altered transcription of 20-HSD and P450arom may be involved in the mechanism of B[a]P-induced reproductive toxicity.
Key words: zebrafish, benzo[a]pyrene, steroidogenic enzymes, gene expression