Isolation and characterization of dipeptidyl aminopeptidase IV from human kidney cortex.

Intact dipeptidyl aminopeptidase IV (DAP IV) was solubilized by bromelain treatment from human kidney brush border plasma-membranes. Purification of DAP IV was performed by a 3-step method, applying lectin-affinity chromatography on WGA-Sepharose, gel filtration and anion-exchange chromatography. DAP IV from human kidney cortex showed a pH optimum of 8.7 and was totally inhibited by 1 mmol/l Zn2+. Isolated DAP IV revealed a relative molecular mass of 250 kDa as determined by the native-PAGE method and of 220 kDa by the gel filtration method. Analytical isoelectric focussing of DAP IV revealed an isoelectric point of pH 5.3. Ultrastructural analysis of isolated DAP IV fractions, using the negative staining technique, disclosed the presence of numerous globular particles with an average diameter of 5 nm which correspond to the structural substrate of the purified protein.

Potentiation of aminoglycoside nephrotoxicity by vitamin-D-induced hypercalcemia.

The effect of 1,25(OH)2 vitamin D3-induced hypercalcemia on the course of aminoglycoside nephrotoxicity in the rat was studied. Daily gentamicin, 100 mg/kg body weight, was administered subcutaneously concomitant with 1,25(OH)2 vitamin D3, 50 ng s.c. to male Sprague-Dawley rats. This group was compared to rats injected with gentamicin alone, 1,25(OH)2 vitamin D3 alone, and an ethanol vehicle as a control. Structural and functional parameters of acute renal failure were assessed following 4, 6 and 7 days of treatment. Severe morphologic evidence of tubular injury was documented on day 6 in the group injected with gentamicin and 1,25(OH)2 vitamin D3. Correlative functional and metabolic evidence of tubular cell deterioration occurred in this group on day 7 as represented by an elevated blood urea nitrogen (BUN), 198 +/- 14 mg/dl (p less than 0.001 compared to all other groups), a heightened mean renal cortical homogenate calcium, 1,028.3 +/- 304.8 nmol/mg protein (p less than 0.05 or better compared to all other groups), and significantly increased mean cortical mitochondrial calcium content, 796.3 +/- 116.5 nmol/mg protein (p less than 0.01 in relation to all other groups). Elevated total serum calcium to a level of 11.9 +/- 0.2 mg/dl (p less than 0.001 compared to control group) developed in the gentamicin/1,25(OH)2 vitamin D3 group on day 4, 2 days prior to pronounced structural damage, and continued to be elevated through day 7. No difference in serum phosphorus levels, however, developed between control and gentamicin-plus-vitamin-D-treated animals except on day 7 when severe renal failure developed in this group.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for vitamin D dependent gamma-carboxylation in osteocalcin related proteins.

The content of gamma-carboxyglutamic acid (gla) was determined in rat femoral bone and kidney cortex in rachitic and vitamin D treated animals. It was demonstrated that the level of gla is decreased in vitamin D depleted animals both in kidney cortex and femoral bone. Supplementation of vitamin D deprived animals with this vitamin resulted in an increase in the gla concentration to almost normal levels. Also the incorporation of 14C NaHCO3 in renal cortex microsomes from rachitic animals was blocked. It is suggested that the absence of gla resulted from the direct action of vitamin D on mRNA for the Ca-binding protein.

Renal cortex ion composition and Na-K-ATPase activity in gentamicin nephrotoxicity.

Abnormalities of potassium and magnesium homeostasis have been reported following the use of gentamicin, and potassium depletion enhances gentamicin nephrotoxicity. The present study investigates these relationships in the dog by assessing changes in renal cortex ion composition and renal cortex Na-K-ATPase activity occurring during gentamicin nephrotoxicity. Gentamicin (15 mg/kg i.m. twice daily) was administered for 4 to 7 days to potassium-depleted or potassium-supplemented animals. The results show that gentamicin nephrotoxicity was characterized by a significant reduction in renal cortex content of potassium (17%), magnesium (19%), and phosphorus (12%) in all groups of animals given gentamicin. However, only potassium-depleted animals exposed to 7 days of gentamicin experienced a significant rise in plasma creatinine (from 1.3 +/- 0.1 to 4.3 +/- 1.0 mg/dl). Accompanying this increase in plasma creatinine was a significant rise in the renal cortex content of sodium (from 25 +/- 0.5 to 27.9 +/- 1.7 meq/100 g fat-free dry solid wt) and calcium (from 1.2 +/- 0.1 to 2.6 +/- 0.3 mM/100 g fat-free dry solid wt). Na-K-ATPase activity in the renal cortex fell only in potassium-depleted animals after 4 days (from 11.5 +/- 0.9 to 7.8 +/- 0.1 microM Pi.mg protein-1.h-1) and 7 days (5.9 +/- 0.8 microM Pi.mg protein-1.h-1) of gentamicin treatment. Thus, gentamicin nephrotoxicity is characterized by sequential changes in renal cortex ionic composition, sodium pump activity, and renal function.

Selenium in human tissues from New Zealand.

Selenium concentrations were measured in tissue samples obtained at autopsy from 45 New Zealand residents aged 4 months to 74 yr. Materials included liver, kidney cortex, skeletal muscle, heart, lung, and spleen. Samples of liver and brain were obtained from 16 fetuses (gestational ages, 27-42 wk). Except for kidney cortex, which contained high levels, concentrations of selenium were similar to those reported in other low-selenium areas, and lower than values obtained in selenium-adequate localities.

Mesangiocapillary glomerulonephritis in lambs. III. Quantitative and qualitative aspects of immunopathology.

Newborn Finnish Landrace lambs subsequently affected with mesangiocapillary glomerulonephritis (MCGN) were deficient in the third component of complement (C'3), serum levels being approximately 5 per cent. of those in unaffected lambs. Hypocomplementaemia persisted until symptoms of renal failure occurred at around 6-8 wk of age. Immunofluorescence examinations of renal cortex with antisera specific for IgG, IgM, IgA, C'3 and fibrin supported previous morphological evidence of a strong similarity between this disease and MCGN in man. Similar examinations of choroid plexus suggested that immune complexes containing IgG, IgM and C'3 were present in the interstitium.

The urinary concentrating defect in the Gunn strain of rat. Role of bilirubin.

The role of high serum and tissue levels of unconjegated bilirubin in the pathogenesis of the impaired urinary concentrating ability was investigated in homozygous (jj) Gunn rats with the congenital absence of hepatic glucuronyl transferase. Continuous phototherapy with blue fluorescent lights at a wave length of 460 nm or oral cholestyramine feeding or both reduced serum levels of unconjugated hilirubin to levels consistently below 3.0 mg/100 ml for several weeks in both weanling and adult jj Gunn rats. The renal concentrating defect was already present in weanling jj Gunn rats by 21 days of age. In treated weanling jj animals, maximum concentrating ability and the concentration of urea and nonurea solutes in the papilla and medulla, determined after 24 h of fluid deprivation, were normal when compared to unaffected heterozygous (Jj) littermates. Solute-free water reabsorption which is reduced in jaundiced jj Gunn rats was restored to normal in treated weanling jj rats. The tissue concentration of unconjugated bilirubin was reduced throughout the papilla and inner and outer medulla in the treated jj rats in comparison with untreated jj littermates. The defect in urinary concentrating ability was only partially reversible and sometimes irreversible in adult jj rats, probably because of permanent renal parenchymal damage occurring secondary to massive crystalline deposits in the papilla and medulla. It is concluded that unconjugated bilirubin is directly involved in the pathogenesis of the concentrating defect in jaundiced jj Gunn rats.