Kriz W, Elger M, Lemley K, Sakai T
Institut für Anatomie und Zellbiologie, Universität Heidelberg, Federal Republic of Germany.
Kidney Int Suppl. 1990 Nov;30:S2-9.
This paper summarizes our current knowledge of the structural details and probable functional significance of the system of contractile filaments in the glomerular mesangium. The description is based mainly on studies of superficial glomeruli of the rat kidney. The contractile apparatus of mesangial cells consists of microfilament bundles located predominantly within mesangial cell processes. The thickest microfilament bundles occur in the juxtacapillary mesangial cell processes, which directly abut the glomerular capillaries. The effector structure of mesangial cell contractility is the GBM. Mesangial cell processes are connected to the GBM either directly or through the interposition of extracellular microfibrils. In general, the contractile system of the mesangium interconnects opposing parts of the GBM. This arrangement is particularly obvious in the juxtacapillary processes, which underlie a mechanical connection between the GBM at the two opposing mesangial angles of a single capillary. The geometry and structural composition of the contractile apparatus of the mesangium indeed suggest a static rather than a dynamic function. In conjunction with the GBM, the mesangial contractile apparatus seems capable of supporting sufficient wall tension to counteract the distending forces acting across the capillary walls; the apparatus also seems capable of directly balancing the distending forces on the perimesangial walls. Assuming that mesangial cells are capable of isotonic contractions, the effect of such a contraction on capillary diameter and, consequently, on filtration area would be small.
本文总结了我们目前对肾小球系膜中收缩丝系统的结构细节及其可能的功能意义的认识。该描述主要基于对大鼠肾脏浅表肾小球的研究。系膜细胞的收缩装置由主要位于系膜细胞突起内的微丝束组成。最粗的微丝束出现在近毛细血管系膜细胞突起中，这些突起直接邻接肾小球毛细血管。系膜细胞收缩性的效应结构是肾小球基底膜（GBM）。系膜细胞突起直接或通过细胞外微原纤维的插入与GBM相连。一般来说，系膜的收缩系统将GBM的相对部分相互连接。这种排列在近毛细血管突起中尤为明显，这些突起构成了单个毛细血管两个相对系膜角处GBM之间的机械连接基础。系膜收缩装置的几何形状和结构组成确实表明其具有静态而非动态功能。与GBM一起，系膜收缩装置似乎能够支持足够的壁张力，以抵消作用于毛细血管壁的扩张力；该装置似乎也能够直接平衡系膜周围壁上的扩张力。假设系膜细胞能够进行等张收缩，这种收缩对毛细血管直径以及因此对滤过面积的影响将很小。
