Effects Of Active Immunization Against Pregnenolone And Testosterone On Reproduction Traits In Male Rabbits

The main objective of the present study was to investigate the effects of active immunization against pregnenolone and testosterone on reproduction traitsa in male rabbits. The experiment was conducted:Twenty-four4-5months old male New Zealand rabbits were randomly assigned to three groups of eight animals each. Group I was not given any injections, served as control group. Group II was injected pregnenolone, served as pregnenolone immunized group. Group III was injected testosterone, served as testosterone immunized group. The immunized groups were immunized with2ml immunogen using CFA as the adjuvant and received booster immunizations on the week4, using IFA as the adjuvant. Blood samples were collected at Owvp,2wvp,4wvp,6wvp,8wvp,12wvp,16wvp,20wvp,24wvp for determination of blood antibody titer, LH and testosterone level in blood. Blood antibody titer was determined by an enzyme linked immunosorbent assay (ELISA). Plasma concentrations of LH, testosterone were measured by radio immunoassay (RIA). The animals were sacrificed at24weeks after first immunization. The sizes of the testes, histological analysis of the testes, the activities of P450scc,3β-HSD and CYP450-17were determined after slaughtered. Results of this study are as following:After immunization against pregnenolone, the anti-pregnenolone antibody titers (binding percentage%) increased steadily, the antibody titers in immunized animals reached highest level (53.3%±3.6%) on week12after first immunization and reduced slightly since then, but the antibody titers were still keep a high level. Serum testosterone levels were reduced (P＜0.05) as compared to that of controls, serum LH levels were increased as compared to that of control (p＜0.05). The activities of P450scc were reduced as compared to that of controls (p＜0.05), the activities of3β-HSD and CYP450-17were similar to that of controls (p＞0.05), but have a tendency to be reduced. The weight and size of the testes in immunized group were similar to that of controls (p＞0.05). Histological analyses of the testes showed that the lesions occur in immunized animals’ testes and the sperm quantities were reduced as compared to that of controls.After immunization against testosterone, the anti-testosterone antibody titers (binding percentage%) increased steadily, the antibody titers in immunized animals reached highest level (67.8%±2.7%) on week8after first immunization and the antibody titers were still keep a high level. In immunized group, serum testosterone levels were reduced as compared to that in controls (p＜0.05), serum LH levels were increased as compared to that in controls (p＜0.05). The activities of P450scc were reduced as compared to controls (p＜0.05), the activities of3β-HSD were increased as compared to that in controls (p＜0.05), and the activities of CYP450-17were increased as compared to that in controls, although the difference is not significant (p>0.05). The weight and sizes of the testes in immunized group were similar to that of controls (p>0.05), but have a tendency to be increased. Histological analyses of the testes were normal in immunized group.Active immunization against pregnenolone on male rabbits resulted in a marked reduction in plasma testosterone (T) and a marked increase in plasma LH, the lesions occur in testicular tissues and the sperm quantities are reduced as compared to controls. The results demonstrate that immunization against pregnenolone possibly could be an alternative to surgical castration for male rabbits.Active immunization against testosterone on male rabbits resulted in reduction in plasma testosterone (T), the activities of3β-HSD, CYP450-17are increased, the testicular and the sperm development have not been affected. The results demonstrate that immunization against testosterone may reduce males attack and sex behaviors and no negative effect on reproduction performance.