In vivo cryotechnique IVCT and cryobiopsy are useful to examine native immunolocalizations of serum proteins in tissues of animal organs, re ecting their living states. We used both methods to examine some immunolocalized proteins in living rat kidneys with nephropathy induced by puromycin aminonucleoside PAN administration. At day 3 or 9 after intraperitoneal PAN injection, IVCT was performed on the kidneys of anesthetized rats. Urinary proteins excretions increased at day 3 and exceeded 300

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... /day at day 9. Moreover, blood chemistry analyses indicated hypoalbuminemia and renal dysfunction at day 9. At day 3, minimal morphological changes were detected by hematoxylin-eosin HE staining, but albumin and immunoglobulin G1 IgG1 were immunolocalized along the cytoplasm of podocytes and in the apical parts of proximal convoluted tubule epithelial cell. At day 9, erythrocyte intravascular congestion was observed in almost all of the glomerular basement membranes GBMs , with casts in some renal tubules also immunostained for albumin and IgG1. The relative immunoreactivities of albumin and IgG1 were weaker within GBMs, and the deposited renal tubule casts were strongly immunostained, indicating relatively different protein concentrations. Thus, these techniques revealed dynamically changing processes of protein excretion and reabsorption in various nephron segments that enable us to examine the morphofunctional features of animal kidneys in other renal diseases.