SEX-DEPENDENT EXPRESSION OF A TRANSCRIPTION FACTOR, AD4BP, REGULATINGSTEROIDOGENIC P-450 GENES IN THE GONADS DURING PRENATAL AND POSTNATALRAT DEVELOPMENT

We investigated the expression of Ad4BP (also known as SF-2), a transc ription factor regulating steroidogenic P-450 genes, in the steroidoge nic tissues such as adrenal glands, testes and ovaries through the pre natal and postnatal life of rats. Ad4BP was detected in the primordial adrenal glands and gonads of the 13.5 day postcoitum (d.p.c.) fetus. After the appearance of Ad4BP, a steroidogenic P-450 (P-450(SCC)) was also detected in the adrenal glands and its amount increased gradually . In the fetal gonads of 14.5 d.p.c., a significant amount of Ad4BP wa s detected in the somatic cells of the testes, whereas only a trace am ount was present in the ovaries. The sexually dimorphic expression of Ad4BP continued throughout the neonatal age, Drastic alterations occur red during the first to third week of postnatal age accompanied by fun ctional and structural changes of the gonads. The expression of Ad4BP in the testes attained a maximal level one week after birth and decrea sed markedly thereafter. By contrast, increase of Ad4BP in the ovary w as detected after the first postnatal week. Expression of P-450c17 sho wed a good correlation with the proliferation of Leydig cells in the t estes and theca cells in the ovaries. Immunohistochemical studies reve aled the presence of Ad4BP in Sertoli cells as well as Leydig cells up to the pubertal age. In the adult rat testis, however, staining of Se rtoli dells decreased significantly. Ad4BP was detected in granulosa, theca, corpus luteum and interstitial gland cells in the ovary althoug h the expression levels in granulosa cells varied among follicles. It is suggested that the Mullerian inhibitory substance gene may be a tar get of Ad4BP since this gene has a conserved Ad4-binding site within t he promoter, which is recognized by Ad4BP expressed in the fetal teste s.