Normal urinary protein composition in the female Wistar rat and its relationship to the proteinuria induced by intraperitoneal bovine albumin

Changes in lysosome populations in the rat kidney cortex induced by experimental proteinuria

1. Experimental proteinuria (262.9 mg protein/24 hr urine) was induced in rats by repeated intraperitoneal injections of BSA. 2. Hypertrophy of the kidney cortex was significant 8 days after the start of the BSA injections, and the activities of lysosomal enzymes in kidney cortex and urine were significantly higher in proteinuric compared to nonproteinuric rats. 3. Lysosome populations in the kidney cortex were examined by rate sedimentation of the homogenate and by rate zonal and isopycnic centrifugation of the lysosome-rich ML fraction. 4. The activity of lysosomal enzymes in the kidney cortex increased slightly, essentially in the large, fragile lysosomes mainly recovered from the proximal tubule. 5. Proteinuria induced a shift/reduction in the density of small lysosomes from 1.235 and 1.20 g/ml to 1.225 and 1.185 g/ml, respectively. 6. Proteinuria induced a new population of small lysosomes (density 1.185 g/ml) enriched in cathepsin D.

Ultrastructural localization of anionic and cationic ferritin in the rat glomerular basement membrane in protein-overload proteinuria

The penetration into the glomerular basement membrane of anionic and cationic ferritin has been studied in rats made proteinuric by intraperitoneal administration of bovine serum albumin. In comparison with control animals anionic ferritin penetrated the glomerular basement membrane to a much greater extent in proteinuric rats. Some ferritin particles were observed in small invaginations of the epithelial cell membrane adjacent to the glomerular basement membrane and incorporated in pinocytotic vesicles within the epithelial cell cytoplasm. This was not seen in control animals. Cationic ferritin distribution in the glomerular basement membrane was similar in control and proteinuric rats suggesting that the increased anionic ferritin penetration observed occurs without any reduction in fixed anionic charge.

A morphometric, biochemical and histochemical comparison of puromycin aminonucleoside and hyperalbuminaemic induced proteinurias in the female Wistar rat

Biochemical, immunological, histochemical and electron microscope morphometric techniques were used to monitor the changes in urinary protein composition, albumin clearance and glomerular ultrastructure induced in female Wistar rats following i.p. injection of puromycin aminonucleoside (PAN) or bovine albumin (BSA). BSA injected rats maintained a high degree of selectivity with albumin constituting 90 per cent. of the total protein excreted even when mean protein excretion was in the order of 500 mg/24 hr. A similar degree of selectivity was only evident in PAN nephrotic rats at low levels of proteinuria. Levels of 500 mg/24 hr only 57 per cent. of the total protein was albumin. These differences correlated well with the increased number of glomeruli from PAN nephrotics compared with hyperalbuminaemic rats which, at these high levels of proteinuria, had bare areas of glomerular basement membrane caused by epithelial cell detachment (88 and 7 per cent. respectively). Detailed electron microscope morphometric and immunohistochemical studies showed that there were also important quantitative differences in a number of superficially similar glomerular structural alterations. In PAN nephrotic rats all glomeruli showed very marked epithelial cell foot process loss and reduced staining with colloidal iron. In glomeruli from hyperalbuminaemic rats there was a wide variation in the extent of epithelial cell foot process loss and reduced colloidal iron staining was only demonstrable in those glomeruli which had swollen epithelial containing large numbers of vacuoles and protein droplets. Similarly, while protein droplets were smaller and less numerous in glomeruli from PAN-injected rats, they were present in most glomeruli whereas their distribution was much more variable in glomeruli from BSA-injected rats. All the data collected therefore indicated that there were important differences in the types of proteinuria and glomerular ultrastructural damage present in PAN nephrotic and hyperalbuminaemic rats and suggested that their induction may have involved entirely different mechanisms. Evidence gathered from one experimental model should thus only be used with extreme caution to aid in interpretation of data obtained from the other.