초록
본 연구는 북방산개구리의 난자 및 배아를 활용하여 난자성숙현상과 배아발달과정에 미치는 $Cd^{2+}$의 독성효과를 조사하였다. 결과 $Cd^{2+}$ 0.1ppm에서 난자의 성숙현상을 억제하였으며 $Cd^{2+}$ 작용의 가역성을 조사하기 위해 3시간 동안 난자들을 $Cd^{2+}$에 노출시킨 후 보통배양액으로 옮겨 17시간 배양한 결과 1ppm에서는 가역성을 나타내었으나 2.5ppm에서는 비가역적 인 손상을 주었다. 발달 중인 2세포 배아를 $Cd^{2+}$의 여러 농도에 노출시킨 결과 0.1ppm에서 발달이 억제되었으며 노출시간이 길어진 32세포 시기에는 세포붕괴현상을 유발하였다. 한편, 포배기 배아를 $Cd^{2+}$의 여러 농도에 노출시 켜 96시간 배양한 후 유생의 치사율 및 기형율을 대상으로 probit 분석법으로 조사한 결과 LC50은 0.1ppm, EC50은 0.08ppm, TI는 5.0을 나타내어 $Cd^{2+}$은 높은 치사율을 나타내는 물질로 나타났다. 기형 양상은 척추기형이 0.05ppm에서 14.3%,꼬리기형이 0.1ppm에서 75.0%,복부기형 이 0.01ppm에서 66.7%를 나타내었고 profound형 기형이 0.1ppm에서 25.0%를 각각 나타냈으며 $Cd^{2+}$ 0.1ppm에서 머리에서 꼬리까지의 성장을 억제하였다. 결론적으로 본 연구의 결과들은 $Cd^{2+}$이 난자성숙, 난할 및 배아의 발달과정에 높은 독성의 효과를 가짐을 나타낸다.
This study investigates the toxic effects of $Cd^{2+}$on frog (Rana dybowskii) by the determination of oocyte maturation and development of embryo exposure to different concentrations of the toxicant. The results show that $Cd^{2+}$ concentration of 0.1ppm suppressed the maturation of the oocytes. To examine the reversibility of the inhibitory effects, the oocytes were exposed to the $Cd^{2+}$ only for 3 hours, and then transferred to plain medium and cultured further for 17 hours. The oocytes were recovered from the toxic effect of the $Cd^{2+}$ when they were exposed to 1ppm, but not to 2.5ppm of the $Cd^{2+}$. The development of 2 cell embryos to 32 cell was completely suppressed at 0.1ppm and the longer the embryos were exposed to the $Cd^{2+}$, the more damage appeared to the embryos and the cytolysis of the 32 cell was induced by $Cd^{2+}$ at 0.1ppm. On the other hand, the embryos of blastula stage were cultured 96 hours in presence of the $Cd^{2+}$ at various concentrations and were examined. The rates of mortality and malformed larvae were investigated by probit analysis. From the results of LC$_{50}$ of 0.1ppm and EC$_{50}$ of 0.08ppm, Tl of 5.0 was derived, which indicates $Cd^{2+}$ is to be considered a teratogenic compound. Such specific malformations occurred in 14.3% as spine deformations at the 0.05ppm, in 75.0% as tail deformations at the 0.1ppm, in 66.7% as abdominal deformations at the 0.01ppm and in 26.0% as profound deformations at the 0.1ppm of $Cd^{2+}$ concentration which living embryos were exposed to. $Cd^{2+}$ suppressed growth to head-tail length at 0.1ppm. In conclusion, The study results reveal that $Cd^{2+}$ must be considered highly toxic effect to oocyte maturation and embryonic development.