Rat gonadal and ovarian organogenesis with and without germ cells. An ultrastructural study

Abstract

Busulphan (1, 4-butanediol dimetanosulfonate) a drug which selectively destroys primordial germ cells (PGC) was used to study its effects on the morphogenesis of the rat gonads. Undifferentiated gonads and ovaries taken daily from day 11 to birth were studied employing high resolution light and electron microscopy techniques. In these conditions it was established that PGC can be eliminated before arriving at the genital ridge when the drug is administered on the 11 day post coital. The absence of PGC does not prevent the initial proliferation of the somatic cells of the genital region. The morphogenetic events leading to the formation of an undifferentiated gonad, early sex differentiation and the establishment of an ovary are the same in sterilized and untreated embryos. Rat gonadal primordium developes from a blastema formed by proliferation of mesothelial and mesenchymal cells. The basal lamina of some mesonephric tubules is broken on one side and makes continuity with the forming basal lamina of the mesothelium of the genital ridge. In earlier stages mesonephric cells seem to freely mix with the other cells. From the blastema gradually emerges an epithelial tissue enveloped by a common basal lamina which includes the surface epithelium, epithelial “cords” and some mesonephric tubules. Early sex differentiation was determined by the precocious separation of the two latter tissues from the former in male embryos. In ovaries this epithelial tissue with or without germ cells maintains its identity the whole gestational life.