© 1993 Oxford University Press
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Reproductive and Thyroid Effects of Low-Level Polychlorinated Biphenyl (Aroclor 1254) Exposure1
*Reproductive and Perinatal Toxicology Branches, DTD, HERL, MD-72, United States Environmental Protection Agency, Research Triangle Park North Carolina, 27711
ManTech Inc., Research Triangle Park North Carolina 27711
Received June 29, 1992; accepted October 2, 1992
As little information is available on the adverse effects of polychlorinated biphenyls (PCBs) on the reproductive system of the male rat, the current study was conducted to evaluate the effects of subchronic administration of the PCB mixture Aroclor 1254 on testicular gamete production and endocrine function. The thyroid hormone thyroxine (T4), which is critical for reproduction and development, was also measured because of the well-documented effects of PCBs on this hormone. Weanling (31-day-old) male Fischer rats were administered 0, 0.1, 1, 10, or 25 mg/kg/day Aroclor 1254 by gavage for 5, 10, or 15 weeks and necropsied. The hormones testosterone (T) and thyroxine were measured in the serum, and body weight and weights of the liver, kidney, testes, seminal vesicle plus coagulating gland, cauda epididymides, and pituitary were taken. At 10 and 15 weeks, testicular interstitial fluid (IF) was collected and T concentration in the IF was measured. Sperm motility was measured from a caudal sperm sample and sperm numbers in the testis and cauda epididymis were determined. In addition, tissues were examined microscopically for histopathological alterations. In the high-dose group, body, seminal vesicle, cauda epididymal, and pituitary weights were depressed at 10 and 15 weeks and cauda epididymal sperm numbers were reduced after 15 weeks of dosing. In contrast, testes weights, testicular sperm numbers, sperm motility, and serum and testicular testosterone levels were unaffected, even in the highest dose group (25 mg/kg/day). Aroclor 1254 administration produced histological alterations in the liver and kidney at doses of 1.0 mg/kg/day and above. These results indicate that the testis of the rat is not a specific target organ for Aroclor 1254. In contrast, serum T4 levels were reduced by Aroclor 1254 administration at a dose 250-fold below the dose that failed to alter testicular function. Serum T4 levels were depressed 25% in the 1 mg/kg dose group after 5 weeks of exposure and 30% in the 0.1 mg/kg group following 15 weeks of exposure. T4 levels were undetectable in the two highest (10 and 25) dose groups at all intervals. The fact that the decreases in T4 were generally concurrent with increases in liver weight suggested that Aroclor 1254 altered T4 levels by increasing the turnover rate in the serum by enhancing the metabolism of T4 by the liver. The reduction in serum T4 reported here occurred at a dose 25-fold lower than the dose generally recognized as affecting thyroid hormone levels.