Daily amounts of urinary protein were shown in Fig. 24.2, depending on the days after the PAN injection and also administered PAN concentrations. The excreted protein amount was not increased in the control group (Fig. 24.2a). In the experimental group of 15 mg PAN injection, the amount of urinary protein was increased at day 3 and exceeded 300 mg/day at day 9 (Fig. 24.2a). In the lower 5 or 10 mg PAN-injection group (Fig. 24.2b), the protein amount in the urine was also slightly increased at day 3. Table 24.1 shows a list of biochemical analyses of serum albumin and creatinine. Significant hypoalbuminemia and renal dysfunction s were detected in the 15 mg PAN-injection group at day 9. In the 5 or 10 mg PAN-injection group, hypoalbuminemia was also detected at day 3.

With HE staining, light micrographic images of normal rat kidneys were clearly observed without ischemia nor anoxia (Fig. 24.3a, b). Various shapes of erythrocytes reflecting their flowing condition in glomerular basement membrane s (GBMs) were well retained in the HE-stained tissue sections (Fig. 24.3b; arrows). By immunostaining for albumin , its immunolocalization of the normal kidneys was mainly detected in GBMs and blood vessel s in the interstitium between proximal or distal convoluted tubules (Fig. 24.3c, d). At higher magnification of a glomerulus (Fig. 24.3d, e), it was rarely detected in the outside of GBMs. In addition, the albumin immunolocalization was also detected at intercellular digitation or basal striations (Fig. 24.3f) and the apical cytoplasm of epithelial cell s in some proximal tubule s (PTs) at higher magnification of PTs (Fig. 24.3f). Immunolocalizations of IgG1 in normal rats were detected in GBMs and blood vessels of the interstitium (Fig. 24.3g, h). At higher magnification of a glomerulus (Fig. 24.3h, i), it was rarely detected in the outside of GBMs in the similar pattern of albumin. At higher magnification of PTs (Fig. 24.3j), it was rarely immunolocalized at basal striations unlike albumin. By the double-fluorescence staining with PAS and for albumin observed with confocal laser scanning microscopy , the albumin immunolocalizations were detected in the inside of GBMs (Fig. 24.3k–n) and in the apical cytoplasm of epithelial cells of PTs (Fig. 24.3o–r; arrows).

At day 3 (Fig. 24.4), little histological changes were detected by HE staining at a light microscopic level (Fig. 24.4a, b), as compared to those of the normal rats. On the other hand, albumin was immunolocalized in GBMs and blood vessel s in the interstitium between proximal or distal convoluted tubules (Fig. 24.4c), which were almost similar to those of normal kidneys. At day 3, when an increase of the urinary protein excretion was confirmed by the urine test (Fig. 24.2), albumin was clearly immunolocalized in the outside of GBMs (Fig. 24.4d; arrows). At higher magnification of a glomerulus (Fig. 24.4e; arrows), it appeared to be detected in podocytes , probably indicating their absorption of albumin. The similar albumin absorption into podocytes was detected in all nephrons (data not shown). At higher magnification of PTs (Fig. 24.4f), granular immunoreaction products were detected at the apical cytoplasm of proximal tubular epithelial cells, indicating abundant reabsorption of excreted albumin (Fig. 24.4f; arrowheads). A number of proximal tubule s with such reabsorption were significantly increased, as compared to those in control rats. At day 3, IgG1 was also immunolocalized in the outside of GBMs (Fig. 24.4h; arrows). At higher magnification of a glomerulus, granular appearances of the immunoreaction products in podocytes were larger and clearer than those of the albumin (Fig. 24.4i; arrows). At higher magnification of PTs (Fig. 24.4j, arrowheads), granular immunoreaction products in the apical cytoplasm of epithelial cells were clearly detected. By double-fluorescence staining with PAS and albumin, albumin immunolocalizations were detected along GBMs (Fig. 24.4k–n), in podocytes at outer side of GBM (Fig. 24.4k–n; arrows), and at apical cytoplasm of proximal epithelial cell s in PTs (Fig. 24.4o–r; arrowheads).