Honors Theses

Date of Award

2014

Document Type

Undergraduate Thesis

Department

Pharmaceutics and Drug Delivery

First Advisor

Kristine Willett

Relational Format

Dissertation/Thesis

Abstract

Benzo[a]pyrene (BaP) is a polycyclic aromatic hydrocarbon (PAH) that is a known carcinogen that also acts as an endocrine disruptor. Multigenerational impacts of PAH exposure are suggested in human cohort studies. To investigate mechanisms and developmental phenotypes associated with a dietary BaP exposure, zebrafish (Danio rerio) were used. We hypothesized that BaP exposure would cause: 1) phenotypic malformations in the gonad that would affect reproductive success; 2) developmental deformities in the offspring that would lead to decreased survival and ability to reproduce without additional BaP exposure; and 3) changes in gene expression that would be conserved across generations and related to the adverse phenotypes observed. Adult zebrafish (2 females x 2 males, N=10 replicate tanks per treatment) were fed 2% body weight/day flake food treated with 0, 10, 114, or 1012 µg BaP/g flake (equivalent to 0, 0.21, 2.3, and 20 µg BaP/g fish/day) for 22 days. Parental gonads were sectioned and evaluated for pre-vitellogenic, vitellogenic, mature, and corpus atreticum oocytes in females and spermatogonia, spermatocytes, spermatids, and spermatozoa in males. Ovarian atresia was significantly decreased following high dose BaP exposure. The number of fertilized eggs was significantly decreased in F0 fish exposed to 20 BaP/g fish. Total egg production was not significantly affected by dietary exposure to BaP in the F0, F1, and F2 generations. Three subsequent untreated generations of offspring (F1-F3) were assessed for mortality and time to hatch at 24, 32, 48, 56, 72, 80, and 96 hours post fertilization (hpf) and developmental deformities at 96 hpf. F1 (but not F2 or F3) mortality was significantly increased in larvae whose parents were exposed to 2.3 and 20 µg BaP/g fish by 48 and 56 hpf, respectively. Time to hatch in the higher doses significantly decreased in only the F1 generation. F1 body length, body shape, and brain shape were negatively impacted by parental exposure to 2.3 and 20 µg BaP/g fish. Molecular analysis is now being used to elucidate mechanisms that are associated with the phenotypic deformities detected across generations. Supported by NIEHS R21ES019940.

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