Fukushima R, Hato F, Kinoshita Y, Tsuji Y, Kitano A
Department of Physiology, Osaka City University Medical School, Japan.
Cell Mol Biol (Noisy-le-grand). 1997 Jun;43(4):567-79.
Thymus weight and total thymic lymphocyte (TL) number decreased markedly after hypophysectomy (HX). Serum level of insulin-like growth factor-I (IGF-I), one of mediators brought about by growth hormone (GH), reduced considerably after the operation. Exogenous GH stimulation enhanced significantly DNA synthetic activity of TLs from HX group only at lower cell concentrations, less than 5 x 10(5) cell/ml. However, there was not a significant difference in the percentage increase of the TL-DNA synthetic activity with exogenous GH between HX and sham-operated (SO) groups. Since GH-responding TLs appeared to be mature cells and to exist in thymus medulla, the results suggest that rate of the responding cells in the thymus medulla of HX animals is similar to that of SO ones. Furthermore, there was not a significant difference in the percentages of rosette-forming cells and non-rosette-forming cells, reflecting nearly the maturation steps of TLs, between groups. It is difficult to explain such an aspect in spite of severe reduction of TLs after hypophysectomy, since the proliferative-responding rate of TLS to exogenous GH stimulation and the constitutive ratio of each maturation step of TLs in the HX group were almost same as those of SO group. The contradictory data found in thymus after hypophysectomy are discussed from the point of view of the compensatory effects of growth hormone-releasing hormone on TLs from the operated animals.
垂体切除术后，胸腺重量和胸腺淋巴细胞总数显著减少。生长激素（GH）产生的介质之一——胰岛素样生长因子I（IGF-I）的血清水平在术后大幅降低。外源性GH刺激仅在较低细胞浓度（小于5×10⁵个细胞/毫升）时，才显著增强垂体切除组胸腺淋巴细胞的DNA合成活性。然而，垂体切除组与假手术组在外源性GH刺激下胸腺淋巴细胞DNA合成活性的增加百分比上并无显著差异。由于对GH有反应的胸腺淋巴细胞似乎是成熟细胞且存在于胸腺髓质中，结果表明垂体切除动物胸腺髓质中反应细胞的比例与假手术动物相似。此外，反映胸腺淋巴细胞成熟阶段的花环形成细胞和非花环形成细胞的比例在各组之间也无显著差异。尽管垂体切除术后胸腺淋巴细胞严重减少，但垂体切除组胸腺淋巴细胞对外源性GH刺激的增殖反应率和各成熟阶段的组成比例与假手术组几乎相同，这一现象难以解释。本文从生长激素释放激素对手术动物胸腺淋巴细胞的代偿作用角度，对垂体切除术后胸腺中发现的矛盾数据进行了讨论。
