Bassetti M, Huttner W B, Zanini A, Rosa P
Department of Pharmacology, University of Milan, Italy.
J Histochem Cytochem. 1990 Sep;38(9):1353-63. doi: 10.1177/38.9.2387987.
We investigated the co-localization in secretory granules of secretogranins/chromogranins, thyrotropin, and luteinizing hormone in ultra-thin frozen sections of cow anterior pituitary by double immunoelectron microscopy, using specific antibodies and protein A-gold particles of different sizes. The distribution of secretogranin II, chromogranin A, and chromogranin B (secretogranin I) was largely similar. In cells containing secretory granules of relatively small size (100-300 nm) and low electron density (identified as thyrotrophs and gonadotrophs by immunolabeling for the respective hormone) and in cells containing both small (170-250 nm) and large (300-500 nm) secretory granules of low electron density (also identified as gonadotrophs), all three secretogranins/chromogranins were detected in most if not all granules, being co-localized with the hormone. In cells containing both relatively large (400-550 nm), electron-dense granules and small, less electron-dense secretory granules (150-300 nm), identified as somatomammotrophs by double immunolabeling for growth hormone and prolactin, all three secretogranins/chromogranins were predominantly detected in the subpopulation of small, less electron-dense granules containing neither growth hormone nor prolactin. Interestingly, this granule subpopulation of somatomammotrophs was also immunoreactive for thyrotropin and luteinizing hormone. These data show that somatomammotrophs of cow anterior pituitary are highly multihormonal, in that the same cell can produce and store in secretory granules up to four different hormones and, in addition, the three secretogranins/chromogranins. Moreover, selective localization of the secretogranins/chromogranins together with thyrotropin and luteinizing hormone in a subpopulation of secretory granules of somatomammotrophs indicates the preferential co-packaging of the secretogranins/chromogranins and these hormones during secretory granule formation.
我们使用特异性抗体和不同大小的蛋白A-金颗粒，通过双免疫电子显微镜技术，研究了牛垂体前叶超薄冰冻切片中分泌粒蛋白/嗜铬粒蛋白、促甲状腺激素和促黄体生成素在分泌颗粒中的共定位情况。分泌粒蛋白II、嗜铬粒蛋白A和嗜铬粒蛋白B（分泌粒蛋白I）的分布大致相似。在含有相对较小（100 - 300 nm）且电子密度低的分泌颗粒的细胞中（通过对相应激素进行免疫标记鉴定为促甲状腺激素细胞和促性腺激素细胞），以及在含有低电子密度的小（170 - 250 nm）和大（300 - 500 nm）分泌颗粒的细胞中（也鉴定为促性腺激素细胞），在大多数（如果不是全部）颗粒中都检测到了所有三种分泌粒蛋白/嗜铬粒蛋白，它们与激素共定位。在含有相对较大（400 - 550 nm）、电子密度高的颗粒和小的、电子密度较低的分泌颗粒（150 - 300 nm）的细胞中，通过对生长激素和催乳素进行双免疫标记鉴定为生长激素催乳素细胞，所有三种分泌粒蛋白/嗜铬粒蛋白主要在既不含有生长激素也不含有催乳素的小的、电子密度较低的颗粒亚群中被检测到。有趣的是，生长激素催乳素细胞的这个颗粒亚群对促甲状腺激素和促黄体生成素也有免疫反应性。这些数据表明，牛垂体前叶的生长激素催乳素细胞具有高度多激素性，即同一个细胞可以在分泌颗粒中产生并储存多达四种不同的激素，此外还有三种分泌粒蛋白/嗜铬粒蛋白。此外，分泌粒蛋白/嗜铬粒蛋白与促甲状腺激素和促黄体生成素在生长激素催乳素细胞的分泌颗粒亚群中的选择性定位表明，在分泌颗粒形成过程中，分泌粒蛋白/嗜铬粒蛋白与这些激素优先共同包装。
