Distribution of endogenous albumin in the rat glomerulus: Role of hemodynamic factors in glomerular barrier function. Using an ul-trastructural immunoperoxidase technique, the distribution of en-dogenous albumin in the rat glomerulus was delineated under normal and abnormal hemodynamic conditions. Superficial glomeruli in anesthetized Munich-Wistar rats were rapidly fixed in situ by applying glutaraldehyde to the renal surface. Fixed tissue slices were treated with anti-rat albumin Fab fragments conjugated to horseradish peroxidase (HRP), and were then subjected to the Graharn-Karnovsky ultrastructural peroxidase localization pro-cedure. During normal blood flow, dense reaction product specific for albumin was largely confined to the glomerular capillary lumen and endothelial fenestrae, with only small amounts detectable in the lamina rara interna, and none deeper in the basement mem-brane (GBM) or in the urinary space. if cortical tissue was subjected to routine immersion fixation, or if fixation was performed in situ after ligation of the renal artery, reaction product was detected throughout the GBM and in the urinary space. if fixation was performed in situ after ligation of the renal artery and vein (Or artery, vein and ureter), reaction product was found in the GBM and, in very large amounts, in the urinary space. if blood flow was restored for ten minutes after five minutes of renal pedicle (artery and vein) occlusion, the distribution of albumin returned to nor-mal. Thus, glomerular barrier function depends upon the maintenance of normal blood flow conditions.

Distribution de l'albumine endogéne dans le glomérule du rat: role des facteurs hemodynamiques dans Ia fonction de barrière glomérulaire. La distribution de l'albumine endogène dans le glomérule du rat a été précisée dans des conditions hémodynamiques normales et anormales au moyen d'une technique ultrastructurale utilisant l'immunoperoxidase. Les glomérules superficiels de rats Munich—Wistar ont été rapidement fixes in situ par application de glutaraldéhyde a Ia surface du rein. Des tranches de tissu fixé ont été traitées par des fragments Fab anti-albumine de rat conjugués a de Ia peroxydasc du raifort (HRP) puis soumises au procédé de localisation ultrastructurale de Ia peroxydase de Gra-ham-Karnovsky. Quand Ic debit sanguin est normal, Ic produit dense de reaction specifique de l'albumine est principalement localisé dans es lumières des capillaires glomerulaires et les fenétres endothéliales. Dc faibles quantitCs sont détectables dans Ia lamina