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Kathila S. Rajapaksa,
Ph.D. Candidate
Physiological Sciences GIDP
Society of Toxicology
San Diego, California
March 5 – 9, 2006
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“Ovotoxicity Induced by 7,12-dimethylbenz[a]anthracene in a B6C3F1 Mouse Ovarian Culture System”
ABSTRACT
The polycyclic aromatic hydrocarbon, 7,12-dimethylbenz[a]anthracene (DMBA), a known carcinogen destroys ovarian primordial, primary and secondary follicles. The disruption of follicles is attributed to bioactivation of DMBA to a 3,4-diol-1,2-epoxide via CYP 1B1 and mEH. Studies have shown that the ovary expresses catalytically active CYP 450 isoforms and mEH. This study was designed to characterize DMBA induced ovarian effects by determining a concentration and time course of ovotoxicity in an in vitro ovarian culture system. Ovaries from post natal day 4 (PND4) B6C3F1 mice were incubated with vehicle medium (DMSO), or DMBA (0.5, 0.625, 0.75, 1nM) for 15d; and 0, 6, 12, 24, 48, and 96h at 1nM. Following incubation ovaries were prepared for histological evaluation and follicles in every 12th section were classified and counted. Following 15d incubation follicles in DMSO control were: primordial, 251.4±23.35; small primary, 85.4±4.73; large primary, 5.2±1.39; secondary, 2.8±1.39. At that time follicles of all sizes were depleted at every concentration of DMBA. All follicle populations present in the PND4 ovary were significantly reduced (p<0.05) at 96h of incubation with 1nM DMBA compared to 0h control, or 6, and 12h incubation with 1nM DMBA. Primordial follicle loss (p<0.05) was seen within 24h of incubation with 1nM DMBA (0h, 303.67±60.73; 24h, 145.67±34.97; 96h, 30.25±12.95). Small primaries were reduced (p<0.05) by 96h of incubation (0h, 82.33+/19.22; 96h, 32.25+/7.03). Large primary follicle loss (p<0.05) was detected within 24h of incubation (0h, 14.33±2.33; 24h, 5±2.08; 48h, 5.67+/1.20; 96h, 0). Secondary follicles were not present in these ovaries. These data demonstrate that DMBA is ovotoxic to all follicle populations present in the PND4 ovary starting at 96h (4d) of incubation. Thus, these observations along with previous studies support that the PND4 mouse ovary is capable of bioactivating DMBA to its ovotoxic form. (Supported by ES09246)
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