Effects of Heavy Metals on the in vitro Follicular Steroidogenesis in Amphibians

다국어 초록 (Multilingual Abstract)

Heavy metals are well known as importantenvironmental pollutants and also considered as endocrinedisrupters. This study was performed to evaluate the directeffects of heavy metals such as cadmium (Cd), zinc (Zn),mercury (Hg), lead (Pb), cobalt (Co), and arsenic (As) on thevarious steroidogenic enzymes in frog ovarian follicles.Ovarian follicles from Rana catesbeiana were isolated andhomogenate (FPH, 0.05 gland/ml) or various steroid precursorswith or without heavy metals (0.01-100M), and steroidlevels in the follicle or culture medium were measured byradioimmunoassay (RIA). Thus, the steroidogenic enzymeactivities were indirectly evaluated by measuring theconverted steroid levels from the added precursor steroid.Among heavy metals, Hg, Cd and Zn significantly inhibitedFPH-induced pregnenolone (P5) production by the follicles(EC50, 4.0M, 25.6M and 5.7 M, respectively ), and alsosuppressed the conversion of testosterone (T) to estradiol17β (E2) (EC50, 4.2M, 7.5M and 80.0 M) while Pb, Coand As are not or less effective in the inhibition. Otherenzymes such as C 17-20 lyase and 17 β-hydroxysteroiddehydrogenase (17 β-HSD) were suppressed only in thehigh concentration of Hg, Cd and Zn. Taken together, thesedata demonstrate that cytochrome P450 side chain cleavage(P450scc) and aromatase are much more sensitive to heavymetals than other steroidogenic enzymes and Hg, Cd andZn show stronger toxicity to follicles than other heavy metalsexamined.

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