Effects of PCB on Reproductive Success in Sprague-Dawley Rats Exposed to Aroclor 1254 for One Year

Polychlorinated biphenyls (PCB) are environmental contaminants that have been a problem since the 1960s. PCB are a serious concern because they are widespread, lipophilic, and bioaccumulate through food webs concentrating in adipose tissue. PCB are a threat to both wildlife and humans because they elicit metabolic and endocrine disruptions with some problems including hypothyroxinemia, spatial learning and memory deficits, neurochemical and neurobehavioral alterations, and reproductive alterations. Sprague-Dawley rats were obtained that had been exposed to Aroclor 1254® in the diet at 1.25 ppni or 25.0 ppm dosage for one year before being mated. Males and females were placed together in a cage and females were tested each day for a sperm-positive vaginal smear. After a sperm positive vaginal smear, females were housed separately, maintained on their respective diets, and weighed daily until weight gain reversal or miscarriage. All animals in the present study that were fed PCB had weight gain reversal or miscarriage, whereas controls of a similar age all carried pregnancy to term. The results of the present study indicate that continuous ingestion of Aroclor 1254® at low doses has a depressive effect on reproductive success. OHIO J SCI 102 (5):102-105, 2002 INTRODUCTION Polychlorinated biphenyls (PCB) are environmental contaminants that have been a recognized problem since the 1960s (Jacobsen and Jacobsen 1997). PCB are a serious concern because they are widespread, lipophilic, and bioaccumulate through food webs by concentrating in adipose tissue. These contaminants are a threat to both wildlife and humans because they cause metabolic and endocrine disruption (Aronson and others 2000; Gerstenberger and others 2000). Some of the problems associated with PCB include hypothyroxinemia, spatial learning and memory deficits, neurochemical and neurobehavioral alterations, and reproductive alterations (Schantz and others 1997). Accidental ingestion by humans, which occurred in Japan in 1968 and Taiwan in 1979, has caused many long-term effects including hyperpigmentation, inflamed conjunctival glands, and intellectual impairment (Kuratsune and others 1972). As a result of human exposure, PCB have been detected in human serum, adipose tissues, breast tissues, and brain tissues (Aronson and others 2000). Previous studies done in our lab using large amounts of the PCB mixture Aroclor 1254® (62.5, 125, or 250 ppm) in the maternal diet have reported a decrease in body weight, spatial learning problems, and subnormal thyroid status in young rats (Juarez de Ku 1992; Pritts 1996). Using smaller amounts of Aroclor 1254® (1.25, 12.5, or 25.0 ppm) resulted in alterations in pup thyroid status, depressed body weight, and problems in spatial learning in the Morris Water Maze (Pritts 1996; Provost and others 1999). The present study was designed to examine the 'Manuscript received 9 October 2001 and in revised form 20 March 2002 (#01-26). 2 Present Address: Utica College of Syracuse University, 1600 Burrstone Road, Utica, NY 13502. To whom requests for reprints should be addressed. long-term reproductive effects of Aroclor 1254® on animals exposed to a diet containing small amounts of PCB (1.25 and 25.0 ppm) and on the second generation of offspring from animals exposed for one year. MATERIALS AND METHODS Sprague-Dawley rats were obtained from the Bowling Green State University Animal Research Facility. Animals received food and water ad libitum in a temperaturemonitored environment of 20° C and 20-50% humidity. Parents of the animals used in the present study were female rats weighing 225-275 g that were mated to males of the same strain. Once females were determined to be pregnant, confirmed by a sperm-positive vaginal smear, they were caged separately. Rats were fed a diet consisting of standard rat chow (Mowlan Teklad, Madison, WI) with Aroclor 1254® (AccuStandard, Inc., New Haven, CT) added at 1.25 or 25.0 ppm (w/w). Control animals were continued on standard diet after conception. On the third day following birth, litters were culled to eight pups consisting of four females and four males, where possible. The pups remained in the maternal cage until thirty days of age, at which time two rats were removed for use in another study. The remaining six rats were housed three females and three males per cage, where possible. Ten of the rats for the present study were maintained on the control diet of standard rat chow. Six of the rats for the present study were born to mothers fed PCB, and were given a control diet (consisting of standard rat chow with no PCB) at thirty days of age. The remaining thirty rats were left on the PCB-containing diet that their mothers were fed from the first day of pregnancy (standard rats chow containing Aroclor 1254® at 1.25 or 25.0 ppm). At approximately one year of age these female rats were mated to males of the same strain with varying degrees of exposure to PCB. The mating protocol resulted OHIO JOURNAL OF SCIENCE D. A. DONAHUE AND OTHERS L03 in the generation of a total of five groups. Controls consisted of mating pairs of female and male rats that had never been exposed to PCB. Treatment group one consisted of PCB-control males (males exposed to Aroclor 1254® during gestation and for thirty days after birth, then given a control diet) mated to 1.25 ppm Aroclor 1254® females. Treatment group 2 consisted of PCB-control males mated to 25.0 ppm Aroclor 1254® females. The 3 treatment group consisted of males and females both continuously exposed to 1.25 ppm Aroclor 1254® from gestation. The 4 treatment group consisted of males and females continuously exposed to 25.0 ppm Aroclor 1254® from gestation. Females pregnant from these matings were caged separately and weighed daily until birth of pups or miscarriage. Statistical analysis was performed using StatView (SAS Institute, Cary, NC). Statistical significance was ascribed to p <0.05 with ANOVA and Fisher's PLSO was used to detect statistical differences between groups.