Ulisse S, Jannini E A, Carosa E, Piersanti D, Graziano F M, D'Armiento M
Department of Experimental Medicine, University of L'Aquila, Italy.
J Endocrinol. 1994 Mar;140(3):431-6. doi: 10.1677/joe.0.1400431.
Basal and FSH-induced aromatase activity in prepubertal rat Sertoli cells was inhibited by L-triiodothyronine (T3) in a time- and dose-dependent manner. The effect was evident only after 6 h of preincubation with T3 (10(-7) M) and the half-maximal dose was 0.5 +/- 0.2 nM, which correlated with the Kd of the nuclear T3 receptor of rat Sertoli cells (Kd = 1-2 nM). The effect was specific as judged by the lack of effect of the T3 analogue 3-iodo-L-tyrosine. The inhibitory effect of T3 was present over the entire range of FSH concentrations used (0.001-100 ng/ml). In T3-treated Sertoli cells, aromatase activity induced by 8-bromo-cyclic AMP was inhibited by the same order of magnitude as that of FSH, thus suggesting that the inhibitory effect of T3 was downstream from cyclic AMP formation. Furthermore, pretreatment of Sertoli cells cultures with T3 (24 h, 10(-7) M) did not affect basal or FSH-induced extracellular cyclic AMP accumulation. This effect of T3 on rat Sertoli cell aromatase activity may be regarded as a part of the integrated mechanism by which thyroid hormone modulates the functions of the seminiferous epithelium.
L-三碘甲状腺原氨酸（T3）以时间和剂量依赖的方式抑制青春期前大鼠支持细胞中的基础和促卵泡激素（FSH）诱导的芳香化酶活性。只有在与T3（10^(-7) M）预孵育6小时后，这种作用才明显，半数最大剂量为0.5±0.2 nM，这与大鼠支持细胞核T3受体的解离常数（Kd = 1 - 2 nM）相关。根据T3类似物3-碘-L-酪氨酸无作用判断，该作用具有特异性。在所用的整个FSH浓度范围（0.001 - 100 ng/ml）内，T3均有抑制作用。在T3处理的支持细胞中，8-溴环磷酸腺苷（8-bromo-cyclic AMP）诱导的芳香化酶活性受到的抑制程度与FSH诱导的抑制程度相同，这表明T3的抑制作用在环磷酸腺苷形成的下游。此外，用T3（24小时，10^(-7) M）预处理支持细胞培养物不影响基础或FSH诱导的细胞外环磷酸腺苷积累。T3对大鼠支持细胞芳香化酶活性的这种作用可能被视为甲状腺激素调节生精上皮功能的综合机制的一部分。
