Effect of 17β-Estradiol on Somatic and Germ Cell Subpopulations in the Ovary of the Newly Hatched Chick

Abstract

The involvement of estrogens in avian ovary differentiation and morphogenesis has been previously demonstrated by several authors. The aim of the present study is to provide evidence regarding which cell subpopulations of the ovary are target cells for 17β-estradiol during chick development. White Leghorn chick embryos received 200 ng of the hormone or the vehicle on the chorioallantoic membrane at 11, 13, and 15 days of incubation. Within 24 hr after hatching, the left ovary was processed for total cell count, study of the meiotic prophase of oocytes, and the morphometric evaluation of the cortical and the medullary regions of the ovary. Germ cell number was not modified by the treatment. Similarly, no changes were observed in the stage of the prophase and the cellular area of oocytes. The total number of somatic cells was increased in the newly hatched chick ovary treated with 17β-estradiol. The number of undifferentiated cells in the juxtacortical medulla was higher in the treated ovary than in the control group. Moreover, the pregranulosa cells of the cortical region were hypertrophied in the 17β-estradiol treated ovary. However, no changes were observed in the typical steroidogenic cells after the estrogen treatment. In conclusion, two subpopulations of somatic cells are estrogen target cells in the prefollicular chicken ovary: the pregranulosa cells of the ovarian cortex and the undifferentiated cells in the juxtacortical medulla.