The role of steroid hormones in the differentiation of the gonads of the clawed toad, Xenopus laevis Daudin
Past experiments had demonstrated feminization of male larvae of Xenopus by treatment with oestrogens but the androgens available had had only slight effects on gonadal development in this species. The author's experiments confirmed the former effect with oestrogens at concentrations of 25µg/1 to 500µg/1. Feminization was however, prevented by simultaneous administration of actinoraycin D or puroraycin. At the high concentration of 2mg/1, oestradiol caused paradoxical masculinization. The effect of progesterone was likewise dosage- dependent. At low concentrations it had only slight effects while at 500µg/l it accelerated ovarian development. It was again confirmed that testosterone had only slight effects on gonadal development, but it was discovered that 5a-dihydrotestosterone caused a considerable degree of gonadal msculinization in genetic female larvae. It is suggested that the inactivity of testosterone is a consequence of the absence or at least inactivation, in the larva, of the enzyme required to metabolise the androgen into the 5a-form. Cortisone at low concentrations had little effect on gonadal development while the 2mg/l dosage caused partial intersexuality in females. Oestrogens and androgens in addition led to hyperplasia of the interrenal. Furthermore oestrogens, androgens and cortisone induced precocious development of the vasa dfferentia in genetic males. Differentiated gonads of larvae continued to develop well in vitro and they were not affected by oestradiol treatment. Adult ovaries also survived well in vitro but undifferentiated gonads and adult testes disintegrated.