Abstract

OBJECTIVES
The purpose of this experimental study was to investigate the toxic effects of toluene on the placental functions and reproductionin the rat. In this study, the expression of placental prolactin-growth hormone (PRL-GH) and Pit-1 genes, the frequency of placental trophoblast cells, and the reproductive data were analyzed.
METHODS
The pregnancy of the Sprague-Dawley rats (250+/-25 g) was determined by verifying the presence of the copulatory plug or sperm in the vaginal smear and the day on which this was observed was defined as pregnancy day 0. The pregnant rats were divided into three groups. The control group was intraperitoneally (ip) injected with sesame oil, and the other two groups were given either 150 or 750 mg/kg BW/day of toluene resuspended in sesame oil during pregnancy days 7-11 and 16-20. The rats from the three experimental groups were sacrificed on pregnancy days 11 and 20, respectively. The mRNA levels of the PRL-GH, Pit-1a and b isotype genes were analyzed by Northern blot hybridization and Reverse transcription-polymerase chain reaction (RT-PCR), respectively. The hormonal concentration was analyzed by Radioimmunoassay. The frequency of the placental trophoblast cells was determined by means of a histochemical study. Reproductive data, such as the placenta and infnat weight, pregnancy period and litter size were surveyed at pregnancy day 20 and after birth. Statistical analysis was carried out by means of the SAS program (version 8.1).
RESULTS
The mRNA levels of the PRL-GH family genes were reduced in a linear fashion by exposure to toluene. The mRNA levels of the Pit-1a and b isotype genes, which induce the expression of the PRL-GH family genes, were also reduced by exposure to toluene. The placental lactogen Iv and II concentrations in the rat placenta, fetus and maternal blood were also decreased by exposure to toluene. During the last stage of gestation, exposure to a high dose of toluene reduced the frequency of the spongiotrophoblast cells that secrete the PRL-GH hormones. Reproductive data such as the placenta and infant weight, and litter size were reduced, and the pregnancy period was extended in the toluene exposed group as compared with the control group.
CONCLUSIONS
Toluene disrupts the PRL-GH hormone metabolism in the rat placenta and this leads to reproductive disorder.

• Keywords: Pit-1 gene;Placenta;PRL-GH family gene;Reproduction;Toluene