STRUCTURAL-ANALYSIS OF THE FORMATION OF GLOMERULAR MICROANEURYSMS IN THE HABU VENOM MODEL

The goal of this study has been to characterize the process of glomeru lar microaneurysm formation and to separate it from capillary ballooni ng. In the Habu venom model glomerular capillary ballooning and glomer ular microaneurysm formation are seen regularly. The sequence of glome rular lesions leading to a glomerular microaneurysm has been examined and it is clear that the process starts with local mesangiolysis. This may proceed to mesangial expansion and/or ballooning of glomerular ca pillaries but in contrast to ballooning the formation of a glomerular microaneurysm is based on endothelial defects. The process occurs as f ollows: once initiated by mesangial failure lesions extend along the m esangial axis. As long as the extension of the lesion encroaches on di vergent capillary branches, capillary ballooning by ''coalescence'' is the result. This process comes to an end when convergent capillary br anching is reached and two capillaries join. At this point endothelial disruptions occur, blood and mesangial spaces merge and a glomerular microaneurysm is established. Further growth of the microaneurysm occu rs following damage spreading along the lobular axis. The entire proce ss has been reconstructed and is presented in a three-dimensional mode l.