A histochemical study of sex inversion produced by estradiol in chick embryos

Abstract

Forty-five White Leghorn chick embryos were injected on the 4th incubation day with 0·1 mg. estradiol benzoate. Some of them were dissected on the 9th day, their gonads being studied with the digitonine histochemical technique for cholesterol. The rest were dissected either on the 10 th or on the 13th day and used for Δ5-β-hydroxysteroid dehydrogenase histochemical determination. In both groups genetic sex was determined by a chromosome study made on liver cells. The gonads belonging to male embryos contained interstitial cells with cholesterol and enzymatic activity comparable in amount and distribution to those found in normal ovaries. The gonads of female embryos contained apparently normal enzymatic activity but gave negative results with the digitonine technique. Additional experiments were made in order to analyse this fact further. The differentiation, in male embryos, of estrogen-producing cells through the action of estrogens is inferred from our results, and this is explained by supposing that in these cells differentiation is normally inhibited in males by some kind of genetically controlled factor. The action of estradiol would consist in counteracting this inhibition.