膀胱移行上皮の細胞構築的微細構造 第1報: 収縮および伸展による影響について

Abstract

1)ラットおよびヒト正常膀胱粘膜は, 収縮時および伸展時の透過型電子顕微鏡および凍結割断法による走査型電子顕微鏡像より重層上皮と考えた.2)ラット膀胱の収縮および伸展は, 表層細胞においては内腔側の表面形態の変化と細胞質内みられる円盤状空胞の変化により, 中間層や基底細胞においては細胞形態の変化や細胞間の嵌合の変化による考えた.3)ヒト膀胱の収縮および伸展は, 表層細胞においてはラットと同様の変化によると考えたが, 中間層や基底細胞においては細胞形態の変化が主であり, 細胞間隙にみられる細胞膜の稜は変化しない.4)尿・血液関門の1つとして表層細胞間の接着装置複合体が考えられるが, 収縮および伸展によりその結合様式に変化はみられなかった.一部の表層細胞間の結合部にjunctional complexを欠く結合様式が認められ, leak junctionと考えた

The luminal surface and three dimensional architecture during contraction and distension of the normal rat and human urinary bladder mucosa were observed by scanning electron microscopy (SEM) after cryofracture of specimen and by transmission electron microscopy (TEM). The bladder epithelium consists of three distinct types of cells, superficial, intermediate and basal cells. SEM and TEM shows that the epithelium is stratified in various states. Some of the intermediate cells reach the basal lamina by fine cytoplasmic processes, but most of them and superficial cells never directly reach the basal lamina. In the rat bladder, the contracted epithelium consists of three to five cell layers and becomes three cell layers in the distended state. Since neighbouring cells are joined by desmosomes, the contact relations between each cell do not change in contracted and distended states. SEM shows an irregular luminal surface of the superficial cells in contracted state. Under TEM this luminal surface showed a scalloped contour, and most of the cell membranes intruding into the cytoplasm gave the appearance of discoidal vesicles. Between superficial cells there are numerous interdigitations in the distended state which show an accordion-like appearance. Between neighbouring cell layers the interdigitations are deep in the contracted state and shallow in the distended state. In the human bladder, the contracted epithelium consists of six to eight cell layers and becomes three to six cell layers on the distended state. Ultrastructural features of the human bladder epithelium during contraction and distension are basically similar to those of the rat bladder epithelium. In contrast, during contraction and distension mainly cellular shape changes from protruded to flattened, but the microvilli-like membrane junctions between intermediate and basal cell layers demonstrate little change.