Watanabe T, Banno T, Jeziorowski T, Ohsawa Y, Waguri S, Grube D, Uchiyama Y
Department of Cell Biology and Anatomy I, Osaka University Medical School, Japan.
Endocrinology. 1998 Jun;139(6):2765-73. doi: 10.1210/endo.139.6.6059.
Pituitary gonadotropes show sex-related differences in their ultrastructure. Typical gonadotropes of male rats exhibit both large granules, which contain chromogranin A (CgA), and small granules, which contain secretogranin II (SgII). In contrast, typical female rat gonadotropes show only a very few large granules among the numerous small granules. To clarify the nature of the biogenesis of these secretory granules and the effects of sex steroids, the ultrastructural and immunocytochemical changes in gonadotropes were examined in castrated male rats supplied with a testosterone or estradiol implant. In castrated rats, pituitary expression and plasma levels of LH increased drastically, but the pituitary content of CgA decreased. The majority of gonadotropes then showed features of "castration cells" containing many small secretory granules. A testosterone implant to castrated rats remarkably suppressed the expression and circulating levels of LH and increased the CgA content in the pituitary to near-normal levels. In this situation, immunocytochemical studies demonstrated that gonadotropes again exhibited large and small secretory granules with the respective localization of CgA and SgII. On the contrary, in castrated rats supplied with an estradiol implant, the expression and content of CgA in the pituitary were remarkably suppressed, and large secretory granules disappeared from gonadotropes. These results suggest that the expression of CgA in gonadotropes is regulated differently by male and female sex steroids. These different effects of androgen and estrogen on the expression level of CgA are closely associated with the sex-related differences in the ultrastructure of secretory granules within gonadotropes.
垂体促性腺细胞在超微结构上表现出与性别相关的差异。雄性大鼠的典型促性腺细胞既有含嗜铬粒蛋白A（CgA）的大颗粒，也有含分泌粒蛋白II（SgII）的小颗粒。相比之下，典型的雌性大鼠促性腺细胞在众多小颗粒中仅显示极少数大颗粒。为了阐明这些分泌颗粒生物发生的本质以及性类固醇的作用，对植入睾酮或雌二醇的去势雄性大鼠的促性腺细胞进行了超微结构和免疫细胞化学变化的研究。在去势大鼠中，促黄体生成素（LH）的垂体表达和血浆水平急剧增加，但垂体中CgA的含量降低。然后，大多数促性腺细胞呈现出含有许多小分泌颗粒的“去势细胞”特征。给去势大鼠植入睾酮可显著抑制LH的表达和循环水平，并使垂体中CgA的含量增加至接近正常水平。在这种情况下，免疫细胞化学研究表明，促性腺细胞再次表现出分别含有CgA和SgII的大、小分泌颗粒。相反，在植入雌二醇的去势大鼠中，垂体中CgA的表达和含量被显著抑制，促性腺细胞中的大分泌颗粒消失。这些结果表明，雄性和雌性性类固醇对促性腺细胞中CgA表达的调节方式不同。雄激素和雌激素对CgA表达水平的这些不同影响与促性腺细胞内分泌颗粒超微结构的性别相关差异密切相关。
