Effects of maternal exposure to a reconstituted mixture of polychlorinated biphenyls on sex-dependent behaviors and steroid hormone concentrations in rats: dose-response relationship.

In a previous experiment, maternal exposure to a polychlorinated biphenyl (PCB) mixture reconstituted according to the congener pattern found in human breast milk resulted in decreased aromatase activity in the brain of newborn male rats, together with feminization of sweet preference behavior in adult male littermates. Both mixtures led to similar reductions of serum testosterone and testes weights. The purpose of the present study was (1) to examine the dose-response relationship for the reconstituted mixture and (2) to study if the rewarding properties of testosterone are affected at levels sufficient to alter sweet preference behavior. Female rats were fed diets with 0, 5, 20, or 40 mg PCBs/kg diet, resulting in an average daily intake of 0, 0.5, 2, or 4 mg/kg body wt. Exposure started 50 days prior to mating and was continued until birth of the offspring. A dose-dependent elevation of sweet preference was found in adult male offspring, indicating feminization of this sexually dimorphic behavior. Examination of conditioned place preference revealed a preference for the testosterone-paired side at the highest exposure condition. In weanling female offspring, dose-dependent reductions of serum testosterone and estradiol concentrations were detected. In addition, testosterone concentrations were reduced in a dose-dependent manner in adult male littermates long after termination of exposure. PCB concentrations in adipose tissue from offspring of the low dose group (0.5 mg/kg body wt) were approximately 10 times higher than values at the upper margin of current human exposure. Taken together, results indicate long-lasting and dose-dependent changes in sex-dependent behaviors and levels of sex steroid hormones in rats following developmental exposure to a PCB mixture that resembles the breast milk pattern.