Characterization of an experimental model of progressive renal disease in rats

ABSTRACT PURPOSE: To characterize an experimental model of progressive renal disease induced by different degrees of nephrectomy in rats. METHODS: Eighty male Wistar rats were divided into four experimental groups (n=20/group): sham surgery (control group), progressive degrees of nephrectomy leading to mild uremia (group 1), moderate uremia (group 2) and severe uremia (group 3). Ten animals of each group were followed for two or four weeks. At the end, blood and 24-hour urine samples were collected to determine renal function parameters. Urine output and water and food intake were daily monitored. RESULTS: In rats of group 1, serum levels of creatinine and urea and microalbuminuria were increased, while reduced creatinine clearance (p<0.05, compared with control group), without changing blood pressure. Animals of group 2 had more accentuated alterations: increases in urinary output, blood pressure, serum concentrations of urea, creatinine, sodium, potassium, and in microalbuminuria, and reduction of creatinine clearance (p<0.05). Group 3 exhibited even more increased serum concentrations of urea, creatinine, sodium and potassium, blood pressure and microalbuminuria, and decreased creatinine clearance (p<0.05) in comparison with control group and unilateral nephrectomy. CONCLUSION: Progressive nephrectomy in rats seems to be useful to study the physiopathology of chronic kidney disease and its mechanisms of progression.

Estresse oxidativo e aumento da apoptose em neutrófilos de cães com azotemia pré-renal / Oxidative stress and increase in apoptosis index of neutrophils from dogs with prerenal azotemia

O presente trabalho tem como objetivo testar a hipótese de que, à semelhança do que ocorre na uremia, cães com azotemia pré-renal sofrem estresse oxidativo, o qual está relacionado com alterações do metabolismo oxidativo e apoptose dos neutrófilos. Para tal, foi determinada a peroxidação lipídica pela quantificação do malondialdeído (MDA) e o status antioxidante total do plasma de 15 cães normais e 10 com azotemia pré-renal, correlacionando-os com a produção de superóxido e o índice apoptótico dos neutrófilos. As determinações do MDA e do status antioxidante total foram estabelecidas empregando-se um conjunto de reagentes comerciais. Por meio de citometria de fluxo capilar, a produção de superóxido e a apoptose de neutrófilos isolados de sangue periférico foram determinadas utilizando-se a sonda hidroetidina e o sistema anexina V-PE, respectivamente. Cães azotêmicos (26,29±5,32g/L) apresentaram menor concentração (p=0,0264) do antioxidante albumina em relação ao grupo-controle (30,36±3,29g/L) e também uma menor (p=0,0027) capacidade antioxidante total (2,36±0,32 versus 2,73±0,24mmol/L), enquanto não houve alteração da peroxidação lipídica plasmática e da produção de superóxido neutrofílica. Concluiu-se que, à semelhança do que ocorre na uremia, condições azotêmicas pré-renais no cão causam estresse oxidativo e aceleração da apoptose dos neutrófilos.

This study aims to test the hypothesis that, similarly to what occurs in uremia, dogs with prerenal azotemia suffer oxidative stress associated with changes in oxidative metabolism and apoptosis in neutrophils. For this purpose, fifteen normal dogs and ten with prerenal azotemia had lipid peroxidation determined by quantifying the malondialdehyde (MDA) and had plasma total antioxidant status evaluated, correlating them with the superoxide production and apoptotic index of neutrophils. MDA and plasma total antioxidant status were determined using commercial reagents. Using capillary flow cytometry, superoxide production and apoptosis were determined from isolated neutrophils of peripheral blood using the hydrithidine and Annexin V-PE probe system, respectively. Azotemic dogs (26.29±5.32g/L) had a lower concentration (p=0.0264) of the plasma antioxidant albumin than the control group (30.36±3.29g/L) and also had lower (p=0.0027) total antioxidant status (2.36±0.32 versus 2.73±0.24mmol/L), while no alterations were observed in plasma lipid peroxidation and superoxide production. It was concluded that, similarly to what occurs in uremia, prerenal azotemia causes oxidative stress and acceleration of neutrophil apoptosis in dogs.

Response of the growth plate of uremic rats to human growth hormone and corticosteroids

Children with chronic renal failure in general present growth retardation that is aggravated by corticosteroids. We describe here the effects of methylprednisolone (MP) and recombinant human growth hormone (rhGH) on the growth plate (GP) of uremic rats. Uremia was induced by subtotal nephrectomy in 30-day-old rats, followed by 20 IU kg-1 day-1 rhGH (N = 7) or 3 mg kg-1 day-1 MP (N = 7) or 20 IU kg-1 day-1 rhGH + 3 mg kg-1 day-1 MP (N = 7) treatment for 10 days. Control rats with intact renal function were sham-operated and treated with 3 mg kg-1 day-1 MP (N = 7) or vehicle (N = 7). Uremic rats (N = 7) were used as untreated control animals. Structural alterations in the GP and the expression of anti-proliferating cell nuclear antigen (PCNA) and anti-insulin-like growth factor I (IGF-I) by epiphyseal chondrocytes were evaluated. Uremic MP rats displayed a reduction in the proliferative zone height (59.08 ± 4.54 vs 68.07 ± 7.5 æm, P < 0.05) and modifications in the microarchitecture of the GP. MP and uremia had an additive inhibitory effect on the proliferative activity of GP chondrocytes, lowering the expression of PCNA (19.48 ± 11.13 vs 68.64 ± 7.9 percent in control, P < 0.0005) and IGF-I (58.53 ± 0.96 vs 84.78 ± 2.93 percent in control, P < 0.0001), that was counteracted by rhGH. These findings suggest that in uremic rats rhGH therapy improves longitudinal growth by increasing IGF-I synthesis in the GP and by stimulating chondrocyte proliferation.

Dialysis water treated by reverse osmosis decreases the levels of C-reactive protein in uremic patients

Atherosclerosis is a major complication of chronic renal failure. Microinflammation is involved in atherogenesis and is associated with uremia and dialysis. The role of dialysate water contamination in inducing inflammation has been debated. Our aim was to study inflammatory markers in patients on chronic dialysis, before and 3 to 6 months after switching the water purification system from deionization to reverse osmosis. Patients had demographic, clinical and nutritional information collected and blood drawn for determination of albumin, ferritin, C-reactive protein (CRP), interleukin-6, and tumor necrosis factor-alpha in both situations. Acceptable levels of water purity were less than 200 colony-forming units of bacteria and less than 1 ng/ml of endotoxin. Sixteen patients died. They had higher median CRP (26.6 vs 11.2 mg/dl, P = 0.007) and lower median albumin levels (3.1 vs 3.9 g/l, P < 0.05) compared to the 31 survivors. Eight patients were excluded because of obvious inflammatory conditions. From the 23 remaining patients (mean age ± SD: 51.3 ± 13.9 years), 18 had a decrease in CRP after the water treatment system was changed. Overall, median CRP was lower with reverse osmosis than with deionization (13.2 vs 4.5 mg/l, P = 0.022, N = 23). There was no difference in albumin, cytokines, subjective global evaluation, or clinical and biochemical parameters. In conclusion, uremic patients presented a clinically significant reduction in CRP levels when dialysate water purification system switched from deionization to reverse osmosis. It is possible that better water treatments induce less inflammation and eventually less atherosclerosis in hemodialysis patients.

Low and normal, protein diets in chronic uremia: nitrogen and potassium balances and albumin and IgG turnover

Las dietas pobres en proteínas se han usado en el manejo conservador de la insuficiencia renal crónica. Seis pacientes con uremia fueron estudiados en la Unidad Metabólica del INNSZ por tres períodos de 15 días en que recibieron dietas isocalóricas que contenían 0.95 (A), 0.53 (B) y 0.17 (C) g/Kg/ddía de proteínas y una ingesta fija en sodio, potasio y agua. Diariamente se recolectaron orina y heces. Se calculó el balance de nitrógeno (NB) potasio y sodio en los tres períodos dietéticos (ABC). El recambio de Alb de IgG también se estimó con I albúmina y I IgG. Con las dietas A y B el balance de nitrógeno fue positivo, con la dieta C el balance fue negativo pero se acompaño de un descenso importante en el nitrógeno sérico de la urea (SUM). La velocidad de síntesis de la albúmina fue baja en todos los pacientes y no se modificó con ninguna de las tres dietas. La correlación positiva entre los balances de nitrógeno y de potasio fue mejor con las dietas A y B. El descenso en la poza metabólica de nitrógeno de la urea (UNMP), SUN, ácido úrico fósforo y potasio fue más substancial con la dieta C que con la dieta B, sin embargo, aún cuando las condiciones clínicas fueron semejantes con ambas dietas, la dieta B fue mejor tolerada, más agradable al paladar y las condiciones nutricionales logradas mejores