Renal blood flow after bilateral ureteral ligation in the rat

Accumulation of free adduct glycation, oxidation, and nitration products follows acute loss of renal function

Glycation, oxidation, and nitration of endogenous proteins occur spontaneously and these modifications are also present in foods. Increased levels of these chemical changes are associated with chronic renal failure; however, little is known about acute kidney failure. We measured these modifications of plasma protein and related free adducts in plasma following bilateral nephrectomy and bilateral ureteral obstruction. Advanced glycation end-product (AGE) residues of plasma protein were increased 3 h post-surgery, and thereafter slowly decreased in all groups, reflecting changes in plasma protein synthesis and transcapillary flow post-surgery. Ureteral ligation increased oxidation and nitration adduct residues. There were, however, marked increases in AGE, dityrosine, or 3-nitrotyrosine free adducts in both nephrectomized and ureter-ligated rats compared to rats that had undergone sham operations. There were lower modified adduct concentrations in the ureter-ligated compared to the nephrectomized rats, reflecting residual glomerular filtration and tubular removal. There was no increase in glycated, oxidized, and nitrated proteins. Glyoxal and methylglyoxal were also increased in both renal failure models. Our study shows that the acute loss of renal function and urinary excretion leads to the accumulation of AGE, oxidation, and nitration free adducts in the plasma.

Kidney pressures after the release of 24 hours of bilateral ureteral ligation in the rat

Kidney function was studied in rats after the release of 24 hours of bilateral ureteral ligation (BUL). After deligation, natriuresis was observed for 1 day while diuresis persisted up to 4 days. The possible defective collecting tubule to reabsorb sodium may improve within 1 day, since the urinary sodium concentration was well below the sham value. During the early phase of deligation, the glomerular filtration rate (GFR) averaged only 15 per cent of the sham value. Heterogeneity of the surface nephrons was apparent. About 17 per cent of the observed surface nephrons had no tubular fluid flow, suggesting possibly that these nephrons may not contribute to the kidney GFR. In the other 83 per cent of the nephrons, the stop-flow pressure, 29.0 mm. Hg, was lower than the sham value, 33.6 mm. Hg, whereas the proximal tubular pressure of 15.1 mm. Hg was significantly above the sham value of 13.2 mm. Hg. Both these factors may have induced a reduction in the effective filtration pressure, from 20.1 to 13.9 mm. Hg, and may have contributed to the reduction in GFR in those functioning nephrons. Four days later, a similar proportion of the surface nephrons still showed a marked reduction in function, whereas others had improved significantly. The proximal tubular pressure, the stop-flow and the effective filtration pressures approached the sham values. These improvements may be associated with an increase in GFR to 42 per cent of the sham value. It is suggested that the prolong suppression of the kidney GFR may not be due to the drastic change in the glomerular capillary pressure of the surface nephrons, at this latter period.