Goulet Benoît N, Hontela Alice
Département des Sciences Biologiques, TOXEN Research Center, Université du Québec à Montréal, C.P. 8888, Succursale Centre ville, Montréal, Québec, Canada, H3C 3P8.
Environ Toxicol Chem. 2003 Sep;22(9):2106-13. doi: 10.1897/02-255.
The effects of cadmium, endosulfan, and atrazine on corticosterone secretion and viability of adrenal cells of African clawed frog (Xenopus laevis) and bullfrog (Rana catesbeiana) were assessed in vitro using a new bioassay. The bioassay relies on stimulation with adrenocorticotropic hormone (ACTH), the endogenous secretagogue for corticosterone secretion, and with dibutyryl cyclic adenosine monophosphate (dbcAMP), an analogue of cAMP, to pinpoint the site of action of the xenobiotics within the steroidogenic cell. To compare the test toxicants according to their endocrine-disrupting potential, the lethal concentration needed to kill 50% of the cells:effective concentration of 50% (LC50:EC50) ratio was calculated, with LC50 as the concentration that kills 50% of the steroidogenic cells and the EC50 as the concentration that impairs corticosterone secretion by 50%. The higher the ratio, the higher the potential for endocrine disruption. Atrazine had no affect on cell viability and on corticosterone secretion in X. laevis, but its endocrine-disrupting potential was high in R. catesbeiana. The LC50:EC50 ratio for cadmium and endosulfan in X. laevis was 26.07 and 1.23, respectively, and for atrazine, cadmium, and endosulfan in R. catesbeiana it was 909, 41, and 3, respectively. The dbcAMP did not restore corticosterone secretion in the cells exposed to the test toxicants in both species. Our study suggests that the secretory capacity of adrenal cells of amphibians can be impaired by environmental chemicals, especially atrazine in the bullfrog, and that these adrenotoxicants disrupt the enzymatic pathways leading to corticosterone secretion downstream from the step-generating cAMP.
采用一种新的生物测定法，在体外评估了镉、硫丹和阿特拉津对非洲爪蟾（非洲爪蟾）和牛蛙（牛蛙）肾上腺细胞皮质酮分泌及活力的影响。该生物测定法依赖于促肾上腺皮质激素（ACTH）（皮质酮分泌的内源性促分泌素）和二丁酰环磷酸腺苷（dbcAMP）（一种cAMP类似物）的刺激，以确定异生物质在类固醇生成细胞内的作用位点。为了根据其内分泌干扰潜力比较受试毒物，计算了杀死50%细胞所需的致死浓度与有效浓度之比：50%（LC50:EC50），其中LC50为杀死50%类固醇生成细胞的浓度，EC50为使皮质酮分泌减少50%的浓度。该比值越高，内分泌干扰潜力越大。阿特拉津对非洲爪蟾的细胞活力和皮质酮分泌没有影响，但其在牛蛙中的内分泌干扰潜力很高。非洲爪蟾中镉和硫丹的LC50:EC50比值分别为26.07和1.23，而牛蛙中阿特拉津、镉和硫丹的该比值分别为909、41和3。dbcAMP不能恢复两种受试毒物处理的细胞中的皮质酮分泌。我们的研究表明，两栖动物肾上腺细胞的分泌能力可能会受到环境化学物质的损害，尤其是牛蛙中的阿特拉津，并且这些肾上腺毒物会破坏导致皮质酮分泌的酶促途径，该途径在产生cAMP的步骤下游。
