van Haaster L H, de Jong F H, Docter R, de Rooij D G
Department of Cell Biology, Utrecht University, Medical School, The Netherlands.
Endocrinology. 1993 Aug;133(2):755-60. doi: 10.1210/endo.133.2.8344214.
T3 was injected daily in newborn rats from birth to 16 days of age. Control rats received daily injections of vehicle during the same period. The proliferative activity of the Sertoli cells was studied by means of bromodeoxyuridine incorporation, and tubular lumen formation and nuclear size were taken as markers of Sertoli cell differentiation. T3 treatment strongly reduced the proliferative activity of Sertoli cells from day 7 on, and on day 12, proliferation of Sertoli cells had ceased, while in control rats proliferating Sertoli cells were observed up to day 16. As a result of the reduced Sertoli cell proliferation, the final Sertoli cell number per testis at 23 days of age was reduced by 50% from 38 +/- 1 x 10(6) in control rats to 19 +/- 1 x 10(6) in T3-treated rats. Lumen formation in seminiferous tubules of T3-treated rats began at 12 days of age, while in controls lumen formation was first observed at 16 days. The area of the Sertoli cell nuclei was somewhat larger in T3-treated rats on day 16, but not at any other age examined. Body and testis weights in adult rats at 100 days of age were reduced by 46% and 48% of control values, respectively. The high neonatal T3 levels reduced serum levels of TSH on days 7 and 9, but not at any other age examined. FSH levels were reduced in T3-injected rats on days 5 and 7 and increased on day 23, after cessation of treatment. Immunoreactive inhibin-alpha levels were increased on days 5-9 and reduced on days 16 and 23. These findings indicate that T3 stimulates the production of immunoreactive inhibin by Sertoli cells, but also of bioactive inhibin, as indicated by the reduced FSH levels. It is concluded that the levels of thyroid hormones early in life are important for the terminal differentiation of Sertoli cells and, therefore, for determining adult testis size. The data indicate that this might be a direct effect of T3 on Sertoli cells.
从出生到16日龄，每天给新生大鼠注射T3。同期对照大鼠每天注射赋形剂。通过溴脱氧尿苷掺入法研究支持细胞的增殖活性，并将管腔形成和核大小作为支持细胞分化的标志物。从第7天开始，T3处理强烈降低了支持细胞的增殖活性，到第12天，支持细胞的增殖停止，而在对照大鼠中，直到第16天仍观察到支持细胞在增殖。由于支持细胞增殖减少，23日龄时每个睾丸的最终支持细胞数量从对照大鼠的38±1×10⁶减少了50%，降至T3处理大鼠的19±1×10⁶。T3处理大鼠的生精小管在12日龄时开始形成管腔，而对照大鼠在16日龄时首次观察到管腔形成。在第16天，T3处理大鼠的支持细胞核面积略大，但在其他任何检查的年龄均无此现象。100日龄成年大鼠的体重和睾丸重量分别降低至对照值的46%和48%。新生儿期高T3水平在第7天和第9天降低了血清促甲状腺激素水平，但在其他任何检查的年龄均无此现象。注射T3的大鼠在第5天和第7天FSH水平降低，在停止治疗后的第23天升高。免疫反应性抑制素α水平在第5 - 9天升高，在第16天和第23天降低。这些发现表明，T3刺激支持细胞产生免疫反应性抑制素，也刺激产生生物活性抑制素，如FSH水平降低所示。结论是，生命早期的甲状腺激素水平对支持细胞的终末分化很重要，因此对确定成年睾丸大小也很重要。数据表明这可能是T3对支持细胞的直接作用。
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