Localization of orphan receptor TR3 mRNA in early developmental follicles in rat

Abstract

Byin situ hybridization, the localization of orphan receptor TR3 mRNA has been observed in early developmental follicles. TR3 mRNA is first expressed in the ovarian interstitial cells on day 2 after birth, and then in granulosa cells (GC) in primary follicles on day 4. The expression level of TR3 mRNA in GC increases following the follicular development. Its higher expression can be observed in the outer layer of GC and inner layer of theca cells (TC) on day 6, where the cells present active proliferation and differentiation. The expression of TR3 is in an increasing manner until the large antral follicles on day 30. The mRNA is only expressed in the healthy, but not atretic follicles in adult rat ovaries. Injection of epidermal growth factor (EGF) has dramatically enhanced its expression in the early stage of developmental follicles. It is therefore suggested that TR3 may play a role in regulating growth and differentiation of ovarian somatic cells in the early stage, and its expression is regulated by EGF.