砷、汞对大鼠卵黄囊胎盘发育及其早期造血功能的影响

EFFECTS OF ARSENIC AND METHYLMERCURY ON YOLK SAC PLACENTA DEVELOPMENT AND EARLY HEMATOPOIETIC FUNCTION OF RAT

应用全胚胎培养、体内致畸敏感期毒性试验二种方法并结合扫描电镜及光镜技术探讨和比较了砷、甲基汞对大鼠卵黄囊胎盘发育及造血功能的影响.结果发现:砷对卵黄囊胎盘的损害作用远大于甲基汞;光镜下卵黄囊胎盘直径和血管分化得分值逐渐下降,畸胎率随着给药浓度的增加而不断升高,呈剂量-反应关系;扫描电镜下砷组内皮层细胞表面微绒毛数量减少和变短,细胞膜上出现空洞样病变,重者膜崩解残缺不全,间皮层细胞表面微绒毛回缩或消失,细胞膜表面亦有明显的空洞和崩解等病理改变.卵黄囊胎盘-胚胎血循环障碍、微血管数量减少、血岛减少等病变揭示卵黄囊胎盘结构和功能改变与砷的致畸机制关系密切;而汞的致畸机制主要与其直接攻击胚胎细胞有关,但在高剂量时亦对卵黄囊胎盘血管分化有一定的抑制作用.

Using in vitro whole embryo culture and in vivo teratogenic assay, the effects of arsenic and methylmercury on rat yolk sac placenta (YSP) development and hematopoietic function were compared in rat head-fold stage. The results showed that arsenic did more demage to YSP than methylmercury. Under light microscope, the diameter of YSP and the scoring of blood circulation were found to be on the decline and the incidence of terata increased with the increasing concentration of arsenic and methylmercury. Under SEM pathologic changes of endodermal epithelia and mesodermal mesotheia were observed in rats treated with YSP. Thus, a hypothesis for the mechanism of arsenic teratogenesis was proposed, in which arsenic was supposed to interrupt the flow of nutrients to the developint conceptus at a stage of rapid growth and differentiation by virtue of its inhibitory action on YSP-embryo blood circulation and mesenchymal hematopoiesis. It was also noted that the mechanism of methylmercury teratogesis was ralated to its direct cyto-toxicity, and that methylmercury had certain inhibition on YSP blood vessel differentiation at high concentration in particular.