Dowsett K F, Knott L M, Tshewang U, Jackson A E, Bodero D A, Trigg T E
Department of Farm Animal Medicine and Production, University of Queensland, New South Wales.
Aust Vet J. 1996 Sep;74(3):228-35. doi: 10.1111/j.1751-0813.1996.tb15410.x.
To investigate the effect of two dose rates (200 and 400 ng) of a gonadotrophin releasing hormone (GnRH) vaccine on testicular function.
A vaccination dose rate experiment.
Two injections were administered 4 weeks apart to six colts in each treatment group. To maintain immunosuppression until the end of the breeding season, a third injection was given if antibody titres fell below 1000.
Effective antibody titres were present for 12 to 27 weeks. Testosterone concentrations decreased from 2.22 to 0.31 nmol/L 6 weeks after primary vaccination. Androstenedione concentrations decreased from 1.78 to 0.28 nmol/L 5 weeks after vaccination. Testosterone and androstenedione concentrations above 0.69 and 0.87 nmol/L were attained 31 to 43 weeks after vaccination. Mean scrotal widths and lengths decreased over 29 weeks from 9.2 cm and 9.7 cm to 6.7 cm and 7.6 cm. At surgical castration these dimensions were 10.1 cm and 11.0 cm. Mean semen characteristics before vaccination and after recovery were: gel-free volume 16.5 and 13.5 mL, sperm concentration 295.5 x 10(6) and 315.6 x 10(6)/mL, total sperm per ejaculate 4041 x 10(6) and 4657 x 10(6) and live normal spermatozoa 32% and 60%. Histologically, the testes showed active spermatogenesis. The mean testicular parenchyma weights for the 200 and 400 mg groups were 129.0 g and 109.8 g. Daily sperm production per testis and per gram of testis for the 200 and 400 mg groups were 3.7 x 10(8) and 2.8 x 10(6), and 2.3 x 10(8) and 2.0 x 10(6).
Both dose rates suppressed testicular function. Data showed that the vaccine effects were reversible. Individual immune response was less varied in the 200 mg group. Further work is necessary to achieve a less variable response in the immunosuppression of testicular function.
研究两种剂量率（200和400纳克）的促性腺激素释放激素（GnRH）疫苗对睾丸功能的影响。
疫苗接种剂量率实验。
每个治疗组的6匹小马驹每隔4周注射一次，共注射两次。为了在繁殖季节结束前维持免疫抑制状态，如果抗体效价降至1000以下，则进行第三次注射。
有效抗体效价持续12至27周。初次接种疫苗6周后，睾酮浓度从2.22纳摩尔/升降至0.31纳摩尔/升。接种疫苗5周后，雄烯二酮浓度从1.78纳摩尔/升降至0.28纳摩尔/升。接种疫苗31至43周后，睾酮和雄烯二酮浓度分别达到0.69纳摩尔/升和0.87纳摩尔/升以上。阴囊平均宽度和长度在29周内从9.2厘米和9.7厘米降至6.7厘米和7.6厘米。手术去势时，这些尺寸分别为10.1厘米和11.0厘米。接种疫苗前和恢复后的平均精液特征为：无凝胶体积16.5和13.5毫升，精子浓度295.5×10⁶和315.6×10⁶/毫升，每次射精的总精子数4041×10⁶和4657×10⁶，活的正常精子比例32%和60%。组织学检查显示，睾丸有活跃的精子发生。200毫克组和400毫克组的平均睾丸实质重量分别为129.0克和109.8克。200毫克组和400毫克组每只睾丸和每克睾丸的每日精子产量分别为3.7×10⁸和2.8×10⁶，以及2.3×10⁸和2.0×10⁶。
两种剂量率均抑制睾丸功能。数据表明疫苗的作用是可逆的。200毫克组个体免疫反应的差异较小。为了在抑制睾丸功能的免疫反应中实现更小的变异性，还需要进一步开展工作。
