In vitro conversion of androgen to estrogen in amphioxus gonadal tissues

The ability to convert androgen to estrogen (aromatization) is a constant feature of gonadal and neural tissues in all major vertebrate groups. In experiments reported here, the existence of this pathway was investigated in the protochordate amphioxus ( Branchiostoma lanceolatum). Following incubation with [ 3H]19-hydroxyandrostenedione, gonadal homogenates contained authentic estrone and estradiol-17β, as determined by derivative formation and recrystallization to constant specific activity. Cephalic (“brain”) and other segments were aromatase negative. The results indicate that a potential for estrogen biosynthesis in the gonads predates that in other tissues and arises prior to the evolution of true vertebrates.