EFFECTS OF ESTROGENIC HORMONES ON EARLY DEVELOPMENT OF XENOPUS-LAEVIS

Many chemicals released into the environment have estrogenic activity and can disrupt animal development and the function of endocrine syste ms. In order to study the effects of estrogens on aquatic animals, we examined the effects of certain estrogens on early development in Xeno pus laevis. X. laevis embryos were kept in water containing 10(-10), 1 0(-9), 10(-7), 10(-6), and 10(-5) M 17 beta-estradiol (E-2); 17 alpha- estradiol; diethylstilbestrol (DES); 10(-5) M progesterone (P); or dih ydrotestosterone (DHT) beginning at developmental stage 3. Survival ra tes of the embryos developed in water containing 10(-10)-10(-6) M E-2 or DES, all concentrations of 17 alpha-estradiol, and 10(-5) M P or DH T, which were over 70% after stage 48, whereas the rates of the embryo s treated with 10(-5) M E-2 and DES decreased remarkably after stage 2 7 and all embryos were dead by stages 42 and 32, respectively. Embryos treated with 10(-5) M E-2 showed malformations of the head and abdome n and suppressed organogenesis, including crooked vertebrae at stage 3 8; the head was smaller and the abdomen was larger than in the control s. Similar effects were observed in embryos developed in 10(-5) M DES but not in 10(-5) M 17 alpha-estradiol, P, or DHT. After 10(-5) M E-2 treatment, abnormalities were induced only when the treatment was star ted before stage 39. However, on day 30 after fertilization, the stage of the embryos treated with 10(-6) M E-2 was more progressed than tha t of the controls. Estrogen receptor (ER 4) mRNA was examined in eggs, embryos, and adult female liver by reverse-transcription polymerase c hain reaction. ER4 mRNA was expressed in adult liver, unfertilized and fertilized eggs, and embryos, but ER3 mRNA was not expressed. ER4 mRN A in 10(-6) and 10(-5) M E-2-treated embryos showed different expressi on patterns, which may result from the diverse developmental effects o f E-2. The present results demonstrate that 10(-5) M E-2 and DES induc ed embryo death and malformations and that ER may be involved in the i nduction of various developmental defects in X. laevis embryos. (C) 19 97 Wiley-Liss, Inc.