Pituitary somatotropes in ovariectomized rats after treatment with combined lhrh and estradiol

Abstract

Estradiol is important hormone which controls the secretory activity of hormone producing cells in the rat female pituitaries. Luteinizing hormone-releasing hormone (LHRH). found in hypothalamus, primarily controls the release of gonadotropic hormones from the anterior pituitary gland, but also affects some other pituitary cells. In the present study, the influence of estradiol dipropionate (EDP), combined with LHRH, on the morphology and secretory activity of pituitary somatotropes. in ovanctom1zed (ovx) Wistar rat females, was studied. Methods: Female Wistar rats were ovx at 12 weeks of age. Animals were divided into two groups, each comprising seven females. The first group of ovx females received EDP (i.p. 250 µg) daily for 4 weeks, combined with LHRH (i.p. 25 ), during the last three days of the fourth week after the surgery. The second group were ovx controls, who i.p. received the adeqate volume of sterile olive oil and saline during the same period. All females were sacrificed 24 h after the last injection. Pituitary somatotropes were studied using the peroxidase­antiperoxidase (PAP) immunohistochemical procedure. Serum concentrations of growth hormone in control and EDP+LHRH treated female rats were measured by the hGH-Delfia kit. Results: The absolute and relative pituitary weights 1n EDP+LHRH treated females were significantly increased (P <0.05) by 229.7 and 273.7% respectively, in comparison with the controls. lmmunopositive pituitary somatotropes in the control rats were round to pyramidal in shape, usually located in close proximity to the blood vessels. In the EDP+LHRH treted ovx females somatotropes were elongated, irregularly shaped, with more intensely stained cytoplasm. Concentration of growth hormone in the serum of EDP+LHRH treated ovx females was significantly increased (P <0.05) by 60.0%, compared to the Ovx controls. Conclusions: Our findings show that EDP+LHRH application has caused the change in the morphology and stimulated hormone secretion of pituitary somatotropes, in ovx females.