Goericke-Pesch S, Spang A, Schulz M, Ozalp G, Bergmann M, Ludwig C, Hoffmann B
Clinic for Obstetrics, Gynecology and Andrology of Large and Small Animals, Justus-Liebig-University, Giessen, Germany.
Reprod Domest Anim. 2009 Jul;44 Suppl 2:302-8. doi: 10.1111/j.1439-0531.2009.01378.x.
The present study examined the degree to which downregulation with a GnRH agonist impaired spermatogenesis and the time course of morphological and hormonal changes that occurred during recrudescence of spermatogenesis. Using a control group (group 1, n = 5) of dogs, the effect of a removable slow release GnRH-agonist implant was investigated in beagle dogs (group 2, n = 30). The implant was removed after 5 months (week 0) and three to four dogs were castrated at weeks 0, 3, 6, 9, 12, 15, 18, 21 and 24. The degree of downregulation and recrudescence of spermatogenesis was assessed by evaluation of 200 tubular cross-sections, resulting in an assigning of dogs of group 2 to testis developmental groups (DG) according to the most developed germ cell observed: DG A, spermatocytes; DG B, round spermatids; DG C, elongating spermatids and DG D, elongated spermatids. Downregulation led to an arrest of spermatogenesis at the level of spermatogonia/primary spermatocytes. The time course of recrudescence showed high individual variations and the number of dogs falling into DG A, B, C and D was 4, 3, 6 and 17 respectively. Spermatogenesis in group 2, DG D was not different from group 1 (control). In DG A, mean area of Leydig-cell nuclei was lower (p < 0.001) than in the other DG and group 1 and resembled that of juvenile dogs (group 3, n = 3); nuclei of Sertoli cells had changed from more flat/polygonal (group 1, group 2, DG C and D) to round/ovoid and had moved to a more luminal position. As indicated by basal testosterone (T), luteinizing hormone (LH) and follicle stimulating hormone (FSH) concentrations at implant removal, full downregulation had been obtained. Testosterone, LH and FSH concentrations [X(g) (DF), ng/ml] increased (p < 0.05) from implant removal to DG B [T: 0.1 (1.24) vs 2.12 (2.31); LH: 0.2 (2.15) vs 1.11 (1.7); FSH: 0.37 (3.50) vs 6.37 (1.68)] and were more or less constant thereafter indicating that onset of spermatogenesis was related to an increase of plasma T occurring in a very narrow time window. Following GnRH implantation, the size of the testes and the prostate decreased by approximately 55% (p < 0.001), they increased to sizes similar to pre-treatment values following implant removal.
本研究考察了促性腺激素释放激素（GnRH）激动剂下调对精子发生的损害程度，以及精子发生恢复过程中形态和激素变化的时间进程。使用一组对照犬（第1组，n = 5），在比格犬中研究了可移除的缓释GnRH激动剂植入物的作用（第2组，n = 30）。5个月后（第0周）取出植入物，并在第0、3、6、9、12、15、18、21和24周对三到四只犬进行去势。通过评估200个管状横切面来评估精子发生的下调和恢复程度，根据观察到的最发达生殖细胞将第2组犬分配到睾丸发育组（DG）：DG A，精母细胞；DG B，圆形精子细胞；DG C，伸长精子细胞；DG D，长形精子细胞。下调导致精子发生在精原细胞/初级精母细胞水平停滞。恢复过程的时间进程显示出高度的个体差异，落入DG A、B、C和D组的犬只数量分别为4、3、6和17只。第2组DG D中的精子发生与第1组（对照）无差异。在DG A中，睾丸间质细胞核的平均面积低于其他DG组和第1组（p < 0.001），类似于幼年犬（第3组，n = 3）；支持细胞的细胞核从更扁平/多边形（第1组、第2组、DG C和D）变为圆形/椭圆形，并移至更靠近管腔的位置。如植入物取出时的基础睾酮（T）、黄体生成素（LH）和卵泡刺激素（FSH）浓度所示，已实现完全下调。从植入物取出到DG B，睾酮、LH和FSH浓度[X(g) (DF)，ng/ml]升高（p < 0.05）[T：0.1 (1.24) 对 2.12 (2.31)；LH：0.2 (2.15) 对 1.11 (
