Zalewsky C A, Moody F G
Gastroenterology. 1979 Oct;77(4 Pt 1):719-29.
Mucus release was studied in the exposed gastric mucosa of anesthetized fasted dogs using scanning and transmission microscopy as well as histochemical and autoradiographic techniques. Under unstimulated conditions, the gastric epithelium was composed of both nonsecreting and mucus-secreting epithelial cells, with the former being predominant. Nonsecreting cells were characterized by an intact apical mucus package of granules and a continuous plasma membrane. The secreting mucus cell population was found in the foveolar (pit region) as well as interfoveolar areas. Three mechanisms of mucus release were observed: (a) exocytosis, (b) apical expulsion, and (c) cell exfoliation. Evidence for exocytosis was found in all mucus cells, especially in the sulfated glycoprotein-rich foveolar cells. Exocytosis involved only a few granules at a time; this mode of secretion is likely slow and continuous. In contrast, apical expulsion resulted in an explosive release of the entire apical mucus package followed by in situ degeneration of the cell itself. This occurred in the oldest cells forming mucosal crests in the interfoveolar area, whose mucus predominantly stains for neutral glycoproteins. Cell exfoliation, in which the entire cell was extruded into the lumen, was rarely observed and may provide, in addition to apical expulsion, a second mechanism to rid the mucosa of senescent epithelial cells. Mucus secretion is a complex function of the gastric epithelium. The mechanism of secretion and the histochemically defined type of mucus secreted are variables which are dependent on the age of the cell, its position on the foveolae, and the microenvironment within the gastric lumen. The mucus-containing surface and pit cells of gastric epithelium have been described morphologically and ultrastructurally in a number of studies. These cells are highly differentiated, forming a layer which is dynamic and responsive to conditions present in the gastric lumen. Mucus cells arise from multipotent progenitor cells which differentiate in the course of migration up the gastric pits and are involved in the complex macromolecular synthesis of glycoproteins. Although mucus release occurs throughout cell life, very little attention has been given to the cellular ultrastructural changes that deal with mucus secretion. As a result, the mucus-containing surface and pit cells have been described primarily in terms of their nonsecreting functional state. Exceptions to this are a few transmission and scanning electron microscopy studies which describe loss of intact mucus granules, cell extrusion, and in situ degeneration. These previous ultrastructural studies describe cellular patterns, in both normal and injured mucosa, which we fell are related to mucus release. Because of a paucity of knowledge concerning the normal mechanisms of mucus secretion, it was the purpose of this study to define the ultrastructural changes which result in and accompany the production of mucus in canine gastric epithelium.
利用扫描和透射显微镜以及组织化学和放射自显影技术，对麻醉禁食犬暴露的胃黏膜中的黏液释放进行了研究。在未受刺激的条件下，胃上皮由非分泌性和黏液分泌性上皮细胞组成，前者占主导。非分泌性细胞的特征是顶端有完整的颗粒黏液包和连续的质膜。分泌黏液的细胞群体见于胃小凹（隐窝区域）以及胃小凹间区域。观察到三种黏液释放机制：(a) 胞吐作用，(b) 顶端排出，以及 (c) 细胞脱落。在所有黏液细胞中都发现了胞吐作用的证据，尤其是在富含硫酸化糖蛋白的胃小凹细胞中。胞吐作用一次仅涉及少数颗粒；这种分泌方式可能缓慢且持续。相比之下，顶端排出导致整个顶端黏液包的爆发性释放，随后细胞本身原位退化。这发生在胃小凹间区域形成黏膜嵴的最老细胞中，其黏液主要为中性糖蛋白染色。细胞脱落，即整个细胞被挤出到管腔中，很少观察到，除顶端排出外，可能还提供了另一种清除黏膜衰老上皮细胞的机制。黏液分泌是胃上皮的一种复杂功能。分泌机制和组织化学定义的分泌黏液类型是变量，它们取决于细胞的年龄、其在胃小凹上的位置以及胃腔内的微环境。许多研究从形态学和超微结构方面描述了胃上皮含黏液的表面细胞和隐窝细胞。这些细胞高度分化，形成一层动态的、对胃腔内存在的状况有反应的细胞层。黏液细胞起源于多能祖细胞，这些祖细胞在沿胃小凹向上迁移的过程中分化，并参与糖蛋白的复杂大分子合成。尽管黏液释放发生在细胞整个生命过程中，但很少有人关注与黏液分泌相关的细胞超微结构变化。因此，含黏液的表面细胞和隐窝细胞主要是根据其非分泌功能状态来描述的。少数透射和扫描电子显微镜研究除外，这些研究描述了完整黏液颗粒的丢失、细胞挤出和原位退化。这些先前的超微结构研究描述了正常和受损黏膜中的细胞模式，我们认为这些模式与黏液释放有关。由于对黏液分泌的正常机制了解不足，本研究的目的是确定犬胃上皮中导致并伴随黏液产生的超微结构变化。
