Constitutivity of the HCG-receptor protein in the testis of rat and man

Abstract

IN a series of embryological experiments on rabbits and rats, Jost et al.¹ have shown that the manifestation of the male or female phenotype is strictly dependent on the presence or absence, respectively, of testosterone. The Müllerian inhibitor formed by the seminiferous tubules² only seems to be responsible for the retrogression of the Müllerian ducts. Thus, testosterone synthesised in foetal testes³ is the chief organiser of masculine differentiation; a female phenotype results from the absence of testosterone. Accordingly, Ohno⁴ defined maleness as the induced and femaleness as the noninuced state of genital differentation. The androgenic effects on the development of the genital structures occur during successive critical phases. For instance, the stabilisation of the Wolffian ducts in the rat occurs between days 17 and 18 (ref. 1) while the prostate is imposed on day 21 of foetal life. The imprinting of the rat hypothalamus into the male direction, responsible for the masculine secretory pattern of pituitary gonadotrophins and behaviour pattern, is established during the first two days of postnatal life⁵. Castration, hypophysectomy or injections of cyproterone acetate (a highly potent anti-androgen) before these critical stages prevent the differentiation processes but by later treatment the development is no longer affected. Similar developmental patterns may be applicable to man except for hypothalamus differentiation which is fixed as early as in the fifth month of intrauterine life⁶. Full maturity of the genital structures and particularly the onset of sperm production, are both dependent on testicular androgens, so occur rather late during the postnatal life of all mammalian species.