Studies of GnRH-A Active Immunization Effects on LH and FSH Secretion and Histostructure of the Ovary and Uterus in Rabbits

The objective of the study is to investigate the effects of active immunization against gonadotropin releasing hormone agonist (GnRH-A) on secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in the pituitary, and to observe the histological structures and development about ovaries and uteri in female rabbits. 24 female rabbits (Oryctolagus cuniculus) were divided randomly into 4 groups (n=6), namely, experimental group I (EG-I), experimental II (EG-II), experimental III (EG-III), and control group (CG). Rabbits were subcutaneously injected with 1.0 mL GnRH-A (alarelin) antigen respectively at concentrations of 100, 100 and 50 μg mL-1 respectively, in EG-I, EG-II and EG-III. Alarelin antigen was re-injected in EG-II and EG-III with the same dosage on 20 d. CG was a blank. The ovarian and uterine samples were collected aseptically at the end of the experiment of 70 d. The tissue slices were observed under light and electron microscopes. Serum concentrations of LH and FSH were measured with ELISA. The results showed that serum LH concentrations in EG-II and EG-III reached the peak levels on 50 and 40 d respectively, and LH level in EG-II exceeded other 3 groups on 50 d (P<0.05). FSH level in EG-II was higher than those in EG-I, CG (P<0.01) and EG-III (P<0.05) on 40 d. GnRHA could increase the number of primary follicles, enlarge the primary follicle vertical diameter (PFV) and primary follicle transverse diameter (PFT), and promote growth and maturation of follicles. The endometrial epithelium thickness (EET) and uterine wall thickness (UWT) in three EGs were less than that in CG (P<0.05). GnRH-A can increase the quantities of mitochondrial cristaes, cortex granules in cytoplasm, broaden and lengthen zona pellucidas and microvilli of oocytes. It also enlarged nuclei of ooxytes and mitochondria, thereby it promoted the development of oocytes. Re-injection of 100 μg alarelin antigen enhanced the secretion of LH and FSH. GnRH-A promoted the growth and maturation of ovaries and follicles, suppressed uterine development, and also influenced histostructure of ovaries and uteri in female rabbits.