Abstract：To explore a possible reason why the wild So-iuy mullet of Liaodong Bay has high frequency of intersex from the point of view of specie-specific ERα binding sensitivity, a cDNA fragment of 1113 bp encoding So-iuy mullet (sERα) estrogen receptor DEF domain was amplified and used to construct plasmid pGBT9-sERα DEF. pGBT9-sERα DEF was transfected into Y190 yeast cells together with plasmid pGAD424-TIF2 for establishinig the sERα-specific in vitro system in yeast. Then we tested the sERα agonistic affinity of four major environmental estrogenic chemicals including estrone (E1), 17β-estrogen (E2), estrodial (E3) and ethylestrodial (EE2). Their half maximal concentrations (EC50)were calculated to be 3.7, 2.4, 1698.7, 1.2 nmol/L, which are 4.6, 2.3, 3.4, 3.3 times lower than those of Medaka ERα-binding activity, respectively. These results indicate that So-iuy mullet was more sensitive to E1, E2, E3, EE2 than medaka based on their ERα agonistic activity, providing an important clue to elucidate its remarkable occurence of intersex in Liaodong Bay.
