목적: 이 연구는 카드뮴이 흰쥐의 태반 기능과 태자의 발생에 미치는 영향을 연구하고자 하였다. 방법: 실험동물은 15주령의 임신된 F344 Fisher 흰쥐(200±23g)를 사용하였다. 카드뮴(CdCl2)은 생리식염수에 녹인 후 0.5 ㎎/㎏ BW와 5.0 ㎎/㎏ BW의 농도로 임신 7-11일, 16-20일 동안 복강주사하였다. 대조군은 동일한 조건으로 생리식염수를 주사하였다. 유전자 발현은 Northern blot hybridization과 reverse transcription-polymerase chain reaction (RT-PCR) 방법으로 조사하였으며, 호르몬 농도는 방사선면역측정법으로, 태반세포의 빈도는 조직병리학적 소견으로 관찰하였으며, 발생학적 자료는 임신 20일에 제왕절개하여 조사하였다. 자료의 통계적 분석에는 SAS (version 8.1)를 사용하였다. 결과: 카드뮴은 흰쥐태반에서 PRL-GH군 유전자의 발현을 억제하였으며, 이군 유전자들의 전사조절인자인 Pit-1a, b 유전자의 발현도 억제하였다. 카드뮴은 PRL-GH군의 placental lactogen Iv와 Ⅱ호르몬의 농도를 감소시켰다. 고농도 투여군(5.0㎎/㎏ BW) 태반의 junctional zone에서 PRL-GH군 호르몬을 분비하는 spongiotrophoblast 세포의 빈도가 감소되었으며, 부분적인 apoptosis가 관찰되었다. 카드뮴은 태반과 태자의 무게를 감소시켰으며, 수정란의 착상 후 소실을 증가시켜 태자의 수를 감소시켰다. 결론: 임신 중 카드뮴 노출은 태반의 기능을 교란시켜 발생의 장해요인으로 작용한다.
Objectives: This study investigated the toxic effects of cadmium on placental function and reproduction in rats. For this study, the mRNA levels of the placental prolactin-growth hormone (PRL-GH) gene family, placental trophoblast cell frequemcy and reproductive data were analyzed. Methods: Pregnant F344 Fisher rats (200 g±23 g) were intraperitoneally injected with 0, 0.5, and 5.0 ㎎/㎏ B.W/day of cadmium (CdCl2) dissolved in saline from days 7-11 or 16-20 of pregnancy, and were sacrificed at days 11 or 20, respectively. The mRNA levels were analyzed by Northern blot hybridization and reverse transcription-polymerase chain reaction. The hormone concentration was analyzed by radioimmunoassay and the frequemcy of the placental trophoblast cells was observed by histochemical study. Reproductive data were surveyed at day 20 of the pregnancy and after the births. Statistical analysis was carried out using the SAS program (version 8.1). Results: The mRNA levels of the PRL-GH gene family were reduced dose dependently by cadmium. The mRNA levels of Pit-1a and -b isotype genes were also reduced by cadmium. The hormone concentration of PL-Iv and -Ⅱ was decreased by cadmium. During the second half of pregnancy (days 11-21), a high dose of cadmium exposure significantly reduced the frequency of spongiotrophoblast and trophoblast giant cells that secrete the PRL-GH hormones. In the last stage of pregnancy (day 20), a high dose of cadmium exposure induced the apoptosis of spongiotrophoblast cells in the junctional zone of the placenta. Reproductive data such as placental and infant weight, number of live fetuses were decreased, and number of resorptions and dead fetuses, post-implantation loss were increased significantly in the cadmium exposed group compared with the control. Conclusions: Cadmium disrupts the functions of the placenta and these effects leads to reproductive disorders in rats.
