title: Effects of Chromium (VI) Exposure on the Placental Function and Reproduction in Rats.
abstract: OBJECTIVE
  This study aimed to investigate the toxic effects of chromium (VI) on the placental function and reproduction in rats. For the study, the placental prolactin-growth hormone (PRL-GH) gene expression, placental trophoblast cell differentiation and reproductive data were analyzed.
  
  
  METHODS
  The pregnancies of F344 Fisher rats were checked by the presence of a copulatory plug or sperm in the vaginal smear, which was defined as day 0 of the pregnancy. Pregnant rats were divided into the three groups. The control group was given tap water (chromium level < 0.001 ppm) and the remaining groups were given 250 or 750 ppm of chromium (VI) [as potassium dichromate], from day 7 to 19 of the pregnancy. Rats were sacrificed at days 11 and 20 of pregnancy. The mRNA levels of PRL-GH and Pit-1a and b isotype genes were analyzed by Northern blot hybridization and reverse transcriptionpolymerase chain reaction (RT-PCR). The hormonal concentration was analyzed by radioimmunoassay, and the differentiation of placental trophoblast cells were observed by histochemical studies. Reproductive data, such as placental and fetal weights, pregnancy period, and litter size, were surveyed at day 20 of pregnancy and after birth. A statistical analysis was carried out using the SAS program (version 8.1).
  
  
  RESULTS
  The mRNA levels of the prolactin-growth hormone (PRL-GH) family of genes were dose dependently reduced by chromium exposure. The mRNA levels of Pit-1a and b isotype genes that induce the expression of the PRL-GH family of genes were also reduced by chromium exposure. The PRL-GH hormonal concentration in the rat placenta, fetus and maternal blood were decreased by chromium exposure. In the middle stage of pregnancy (day 11), a high dose of chromium suppressed the differentiation of spongiotrophoblast cells that secret the PRLGH hormones. In the last stage of pregnancy (day 20), a high dose of chromium induced apoptosis of placental cells. Reproductive data, such as placental and fetal weights, litter size, were reduced, but the pregnancy period was extended in the group exposed to chromium compared with the controls.
  
  
  CONCLUSIONS
  Chromium (VI) disrupts the ordered functions of the placenta, which leads to reproductive disorders in rats.
authors.affiliation: Department of Occupational and Environmental Medicine, College of Medicine, University of Ulsan, Korea.
authors.forename: Heun
authors.initials: H
authors.lastname: Lee
authors.affiliation: Department of Occupational and Environmental Medicine, College of Medicine, University of Ulsan, Korea.
authors.forename: Jin Ho
authors.initials: JH
authors.lastname: Chun
authors.affiliation: Department of Occupational and Environmental Medicine, College of Medicine, University of Ulsan, Korea.
authors.forename: Deog Hwan
authors.initials: DH
authors.lastname: Moon
authors.affiliation: Department of Occupational and Environmental Medicine, College of Medicine, University of Ulsan, Korea.
authors.forename: Chae Un
authors.initials: CU
authors.lastname: Lee
authors.affiliation: Department of Occupational and Environmental Medicine, College of Medicine, University of Ulsan, Korea.
authors.forename: Sung Goo
authors.initials: SG
authors.lastname: Kang
authors.affiliation: Department of Occupational and Environmental Medicine, College of Medicine, University of Ulsan, Korea.
authors.forename: Byung Chul
authors.initials: BC
authors.lastname: Son
authors.affiliation: Department of Occupational and Environmental Medicine, College of Medicine, University of Ulsan, Korea.
authors.forename: Dae Hwan
authors.initials: DH
authors.lastname: Kim
authors.affiliation: Department of Occupational and Environmental Medicine, College of Medicine, University of Ulsan, Korea.
authors.forename: Chang Hee
authors.initials: CH
authors.lastname: Lee
authors.affiliation: Department of Occupational and Environmental Medicine, College of Medicine, University of Ulsan, Korea.
authors.forename: Jung Won
authors.initials: JW
authors.lastname: Kim
authors.affiliation: Department of Occupational and Environmental Medicine, College of Medicine, University of Ulsan, Korea.
authors.forename: Chae Kwan
authors.initials: CK
authors.lastname: Lee
keywords: Chromium (VI); Growth hormone; PRL; Placenta; Reproduction