Immunopositive ACTH cells in juvenile female rats after treatment with estradiol

Abstract

It was shown that estrogens decreased the POMC gene expression level in female rats. The aim of the present study was to examine the morphometric parameters of immunohistochemically labeled ACTH cells in juvenile female rat pituitaries after estradiol dipropionate (EDP) treatment. The females in juvenile period (16th day) were divided into two groups, each of seven animals. The experimental group received five injections of EDP (i.p. 0.25 mg/kg b.w.) every second day from the 4th to 14th day after birth. The controls were treated by the same schedule with equivalent volume of sterile olive oil. All animals were sacrificed 24 h after the last treatment. Immunopositive ACTH-producing cells were studied using the peroxidase-anti-peroxidase immunohistochemical procedure. The cell volume, nuclear volume and volume density of ACTH cells were determined by the stereological method. The significance of differences between mean values was estimated by Student’s t-test. In juvenile females treated with EDP absolute and relative pituitary weights were significantly increased (P<0.05) by 446.7 and 447.4% respectively, in comparison with the controls. The ACTH cell and nuclei volume as well as their volume density were significantly decreased by 6.4, 33.3 and 46.2% respectively, compared to the controls. In juvenile females immunohistochemically labeled ACTH cells were stellate shaped with the cytoplasmic processes among neighboring cells, localized between the capillaries. The nuclei follow the shape of the cell body. Small, specific secretory granules were distributed mainly at the periphery of the cytoplasm. The shape and localization of ACTH immunoreactive cells in EDP-treated female rats were not significantly changed in comparison with controls. In conclusion, the application of EDP caused the significant decrease of morphometric parameters of ACTH cells in juvenile female rats.