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-17 beta, 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.