神经垂体多肽激素分泌颗粒释放形式和转运途径的形态学研究

A MORPHOLOGICAL STUDY ON THE RELEASING PATTERN AND TRANSPORT ROUTE FOR SECRETORY GRANULES OF POLYPEPTIDE HORMONES OF NEUROHYPOPHYSIS

目的 探讨神经垂体多肽激素分泌颗粒的释放形式和在细胞外正常转运途径的结构基础。 方法 对大鼠神经垂体进行光镜、透射电镜和扫描电镜观察。 结果 神经垂体主要由无髓神经纤维、垂体细胞及富含毛细血管的结缔组织组成。毛细血管内皮为有孔型 (5 0nm) ,外有基膜与血管周隙分隔。完整的大型膜包分泌颗粒 (10 0～ 30 0nm)不仅大量存在于无髓神经纤维内 ,而且也见于血管周隙内。垂体囊由单层扁平上皮细胞和上皮下结缔组织构成 ,囊上皮细胞间存在许多不规则的囊上皮孔 (2～ 5 μm) ,上皮孔附近经常可见分泌颗粒。 结论 这些结构特征提示 ,神经垂体多肽激素或分泌颗粒的释放形式 ,存在一种连同颗粒被膜的整体释放 ;释放入血管周隙内的多肽激素或分泌颗粒 ,更易经组织间隙、囊上皮孔进入脑脊液发挥旁分泌作用 ,而非直接通过毛细血管壁进入血液。

Objective To explore the structural foundation of the releasing pattern and extracellular normal transport route for secretory granules of polypeptide hormones of neurohypophysis. Methods The neurohypophysis of the rat was observed under light microscope, transmission and scanning electron microscope. Results The neurohypophysis was composed of unmyelinated nerve fibres, pituicytes and connective tissue abound in blood capillaries. The endothelium of the blood capillary belonged to the fenestrated type(50nm), separated from the perivascular space by basement membrane. The intact secretory granules(100-300nm) coated with membrane existed not only in the endings of the unmyelinated nerve fibres but also occasionally in the perivascular space. The pituitary capsule was composed of simple squamous epithelial cells and subepithelial connective tissue. Many irregular epithelial openings(2-5μm) were observed among epithelial cells. Secretory granules were seen frequently near the epithelial opening.Conclusion These findings indicate that the releasing pattern of polypeptide hormones or secretory granules of neurohypophysis include a whole releasing together with membrane. The polypeptide hormones or secretory granules released into the perivascular space are easy entering into cerebrospinal fluid by interspace of tissue and epithelial openings rather than into blood stream by walls of capillaries.