Komuro M, Kiuchi Y, Shioda T
Eur J Cell Biol. 1987 Feb;43(1):98-103.
Somatotrophs from male rat anterior pituitary were used to investigate the formation of secretory granules. When enzymatically dispersed cells were incubated with cationized ferritin (CF) for 15 min, CF labeled immature secretory granules, but not mature granules of somatotrophs. Most immature granules labeled by CF transformed to the mature types within 120 min. This indicates that the fusion of endocytic vesicles with the immature granules occurs during the maturation process of secretory granules. The internalized CF was distributed not only in the immature secretory granules, but also in the peripheral region of trans Golgi cisternae or GERL. Enzyme cytochemistry revealed that acid phosphatase-positive cisternae (GERL) were the main site for secretory granule formation, and was devoid of thiamine pyrophosphatase (TPPase) activity. A small number of secretory granules were also present in the peripheral regions of TPPase-positive Golgi cisternae. The granule-forming sites, however, lacked TPPase activity, while the remaining region of the same cisterna showed the positive enzyme activity. This indicates that the granule-forming region at the periphery of Golgi cisterna is different from the remaining part of the same cisterna in terms of cytochemical properties. This probably results from the insertion of endocytic vesicle membrane, since the same granule-forming sites preferentially fused with CF-labeled small vesicles which lacked cytochemical TPPase activity. Taken together. Our results suggest that the membrane of secretory granules is modified during the granule formation, at least partly by the fusion of endocytic small vesicles with Golgi cisternae (or GERL), and with immature secretory granules.
利用雄性大鼠垂体前叶的生长激素细胞来研究分泌颗粒的形成。当用阳离子铁蛋白（CF）孵育经酶分散的细胞15分钟时，CF标记了生长激素细胞的未成熟分泌颗粒，但未标记成熟颗粒。大多数被CF标记的未成熟颗粒在120分钟内转变为成熟类型。这表明在分泌颗粒的成熟过程中，内吞小泡与未成熟颗粒发生了融合。内化的CF不仅分布在未成熟分泌颗粒中，还分布在反式高尔基体潴泡或GERL的周边区域。酶细胞化学显示，酸性磷酸酶阳性潴泡（GERL）是分泌颗粒形成的主要部位，且缺乏硫胺素焦磷酸酶（TPPase）活性。少数分泌颗粒也存在于TPPase阳性高尔基体潴泡的周边区域。然而，颗粒形成部位缺乏TPPase活性，而同一潴泡的其余区域显示出阳性酶活性。这表明高尔基体潴泡周边的颗粒形成区域在细胞化学性质上与同一潴泡的其余部分不同。这可能是由于内吞小泡膜的插入，因为相同的颗粒形成部位优先与缺乏细胞化学TPPase活性的CF标记小泡融合。综上所述，我们的结果表明，分泌颗粒的膜在颗粒形成过程中发生了修饰，至少部分是通过内吞小泡与高尔基体潴泡（或GERL）以及未成熟分泌颗粒的融合实现的。
