Antioxidant and oxidative enzymes were examined in renal glomeruli and proximal tubules of healthy young rats (10‐12 weeks old), and results were related to the superoxide anion generation of these tissues. Activities of superoxide dismutases, catalase, and glutathione peroxidase were 3‐ to 6‐fold higher in proximal tubules than in glomeruli. Similarly, enzyme levels and mRNA levels of superoxide dismutases and catalase were significantly higher in proximal tubules. NADH‐ and NADPH‐dependent oxidase activity and xanthine oxidase activity were not different in glomeruli and proximal tubules. Measurements with lucigenin‐enhanced chemiluminescence in vital tissues indicated 10‐fold higher rates of superoxide anion in glomeruli than in tubules. Compared with the young rats, tubules of 8‐month‐old rats had significantly higher superoxide anion rates and lower superoxide dismutase activity, whereas NADH‐ and NADPH‐dependent oxidase activities were unchanged. We conclude that considerable differences in the antioxidant‐oxidant balance exist between the glomerulus and proximal tubule. Results from experiments using chemiluminescence in vital tissues suggest that changes in the antioxidant‐oxidant balance have an effect on oxygen radical levels. The relevance of the observed differences to glomerular and tubulo‐interstitial disease remains to be determined, but a greater susceptibility of the glomerulus to oxidant stress might be anticipated.

We studied the histo- and immunopathology of the endocrine and exocrine pancreas and a number of other organs in a new insulin-dependent diabetes mellitus (IDDM) rat model (LEW.1AR1/Ztm- iddm rat). The pancreas of the acutely diabetic animals showed an inflammatory infiltrate, involving all islets and ducts. The islet infiltrate was composed mainly of ED1-positive macrophages and T lymphocytes, comprising a large number of CD8(+) lymphocytes and a few CD4(+) lymphocytes. In addition, the islets displayed apoptotic cells, characterized by condensation and fragmentation of nuclear chromatin. These cells were identified as beta cells by insulin immunostaining. Other endocrine and exocrine glands, including adrenals and thyroid, as well as salivary and submandibular glands, were unaffected. Organs from the digestive tract or systemic circulatory system, including small intestine, liver, heart, and lung also showed no involvement. The kidney was intact in acutely diabetic rats. However, 6 months after diabetes manifestation, pathological changes compatible with a diabetic nephropathy had developed, affecting both the glomerula and the proximal tubular segments. It was concluded that the autoimmune process in this new IDDM rat model is restricted to the endocrine pancreas and leads to apoptotic beta cell destruction.

No abstract

Results from several radical scavenger studies indirectly suggested an involvement of reactive oxygen species in the pathogenesis of puromycin aminonucleoside glomerulopathy. In this study, generation of reactive oxygen species was examined directly in glomeruli isolated from rats in the acute phase of puromycin aminonucleoside nephrosis and related to the changes in the glomerular antioxidant defense. Five and nine days after puromycin aminonucleoside injection, gross proteinuria, reduced creatinine clearances, and typical changes of glomerular morphology were present. Levels of reactive oxygen species were increased eightfold in glomeruli isolated 15 min after puromycin aminonucleoside injection, returned to baseline levels on days 1 and 5 after injection, and rose again to 14-fold on day 9 after injection, as determined by chemiluminescence with luminol. Further analysis of increased glomerular radical generation, using the chemiluminescence enhancer lucigenin and different radical scavengers, suggested a predominant involvement of hydroxyl radical and hydrogen peroxide in the initial increase in reactive oxygen species 15 min after puromycin aminonucleoside. Nine days after induction of nephrosis, primarily superoxide anion and hydroxyl radical were found to contribute to increased reactive oxygen species. Despite oxidative stress, antioxidant enzymes were not induced in the course of nephrosis. On the contrary, catalase and glutathione peroxidase activities declined 9 d after puromycin aminonucleoside injection. The results indicate that a transient increase in glomerular reactive oxygen species is sufficient to induce the oxidative glomerular injury observed in this model and that the glomerulus may not necessarily respond to oxidative stress with an induction of antioxidant enzymes.

The water permeability of collecting ducts is greatly increased by the antidiuretic hormone, vasopressin (VP). Freeze-fracture studies were carried out to test if this permeability increase is associated with the appearance of intramembrane particle (IMP) aggregates and whether increased doses of VP lead to an increase in the number and size of particle aggregates in the luminal membrane of principal cells in the isolated cortical collecting duct. Unstimulated cells expressed 17 +/- 6.5 particle aggregates per 100 microns 2. Stimulation with VP at concentrations of 20 or 200 microU/ml increased the number of particle aggregates significantly to 129 +/- 15.8 and 324 +/- 45.8, respectively. The size of the particle aggregates increased from 0.0012 microns 2 under control conditions to 0.025 microns 2 at 20 microU/ml VP and to 0.063 microns 2 at 200 microU/ml VP. In addition, the total area occupied by the IMP increased from 0.02 microns 2/100 microns 2 (controls) to 3.17% and 20.38% (after 20 and 200 microU ADH/ml, respectively). Particle aggregates were also observed in the luminal plasma membrane of isolated collecting ducts fixed immediately after dissection, resembling the in vivo status. These results demonstrate that a dose-dependent relationship exists between the concentration of the applied VP and the number of particle aggregates, as well as the size of the aggregates. Cytoplasmic tubular vesicles in fusion with the apical membrane were observed.