Hans Thysell

The blood serum concentration of cystatin C (γ-trace) as a measure of the glomerular filtration rate

The blood serum concentrations of creatinine and the low molecular weight proteins cystatin C, beta 2-microglobulin and retinol-binding protein were measured in 106 patients whose glomerular filtration rates were assessed by Cr-ethylenediaminetetraacetate (EDTA)-clearance determinations. The reciprocals of the serum concentrations of creatinine, cystatin C and beta 2-microglobulin were closely correlated to the Cr-EDTA-clearance (r = 0.73, 0.75 and 0.70, respectively) in contrast to the corresponding values for retinol-binding protein (r = 0.39). The calculated values of the glomerular elimination rate for creatinine and cystatin C were normally distributed in contrast to those for beta 2-microglobulin. The calculated glomerular elimination rate of cystatin C was not correlated to age, sex, type of disorder or disease activity. The results demonstrate that the serum level of cystatin C is a better measure of the glomerular filtration rate than the serum level of beta 2-microglobulin.

Isolation and characterization of a tumor necrosis factor binding protein from urine

Tumor necrosis factor (TNF)/cachectin can produce both beneficial and harmful manifestations. Mechanisms may operate to counteract potentially harmful effects such as shock and cachexia. The TNF binding protein (TNF‐BP), which is found at increased levels in serum and urine of patients with chronic renal failure, may play such a role. TNF‐BP was purified 1000000–fold to homogeneity from urine of patients with chronic renal failure by use of ion exchange chromatography, affinity chromatography on TNF‐Sepharose and reverese phase chromatography. The purified protein contained only one chain with an apparent Mr on sodium dodecyl sulfate‐polyacrylamide gel electrophoresis of 30000. The aminoterminal amino acid sequence D‐S‐V‐X‐P‐Q‐G‐K‐Y‐I‐H‐P‐Q‐V‐N‐S‐I‐X‐K‐T revealed no significant homologies with previously described protein sequences. TNF‐BP may act as a regulator of the bioactivities of TNF/cachectin.

The effect of reduced glomerular filtration rate on plasma total homocysteine concentration.

The concentration of homocysteine in plasma has been shown to be increased in renal failure, possibly contributing to the accelerated atherosclerosis observed in uraemic patients. The aim of the present study was to document the relationship between plasma total homocysteine (tHcy) concentrations and glomerular filtration rates (GFR) in highly selected patients, with renal function ranging from normal to dialysis dependency. GFR was defined as the plasma clearance of iohexol; a more accurate method than the creatinine-based estimations applied in previous studies. Plasma tHcy concentrations were highly correlated to GFR (r = -0.70, p < 0.0001) and were significantly increased already in moderate renal failure. According to a multiple regression analysis, GFR and red cell folate concentrations independently predicted plasma tHcy concentrations, whereas those of serum creatinine, plasma pyridoxal-5-phosphate, urine albumin and urine alpha-1-microglobulin (a marker of tubular damage) did not. Thus, GFR seems to be a better determinant of plasma tHcy concentration than serum creatinine concentration. Plasma total cysteine and total cysteinylglycine concentrations followed the same pattern as those of tHcy.

Hyperhomocysteinemia in cyclosporine-treated renal transplant recipients.

Moderate hyperhomocysteinemia, an independent cardiovascular risk factor, has been reported in renal transplant recipients. In the present study, plasma concentrations of total homocysteine were significantly increased in 120 renal transplant recipients as compared with 60 healthy controls (19.0 +/- 6.9 vs. 11.6 +/- 2.8 mumol/L, P < 0.0001) and as compared with 53 patients without a transplant but with a comparable degree of renal failure (19.0 +/- 6.9 vs. 16.0 4.9 mumol/L, P < 0.01). There was a significant inverse correlation between glomerular filtration rates and plasma homocysteine concentrations in the renal transplant recipients (r = -0.52, P < 0.0001). Groups of renal transplant recipients, with and without cyclosporine, and renal patients without a transplant were studied; these groups were comparable regarding age, sex distribution, glomerular filtration rate, and folate and vitamin B12 concentrations. Renal transplant recipients on cyclosporine had significantly higher plasma homocysteine concentrations than those not on cyclosporine (19.5 +/- 7.6 vs. 16.2 +/- 4.8 mumol/L, P < 0.05), and the patients without a transplant (19.5 +/- 7.6 vs. 16.0 +/- 4.9 mumol/L, P < 0.01). Thus, the hyperhomocysteinemia of renal transplant recipients not treated with cyclosporine, and that of renal patients without a transplant probably is explained by the same mechanism: renal insufficiency. An additional mechanism seems to operate in renal transplant recipients treated with cyclosporine. The lack of correlation between the concentrations of plasma homocysteine and red cell folate in these patients suggests that cyclosporine interferes with folate-assisted remethylation of homocysteine. Plasma homocysteine concentrations were significantly increased in 24 patients with a history of atherosclerotic complications as compared with the remaining 96 renal transplant recipients (20.8 +/- 4.4 vs. 18.5 +/- 7.3 mumol/L, P < 0.01).

A tumor necrosis factor binding protein is present in human biological fluids

Tumor necrosis factor (TNF) possesses both beneficial and toxic bioactivities. Mechanisms may operate to counteract harmful effects. We have identified a TNF binding protein (TNF‐BP), which shows increased levels in serum and urine of patients on regular hemodialysis treatment (RDT). TNF‐BP inhibited the specific binding of human recombinant TNF (rTNF) to its cell surface receptor. Results from gel chromatography demonstrated the presence in serum and urine of a macromolecule with an apparent molecular weight of 50000, which formed a complex with rTNF. A 62‐fold purification of TNF‐BP from urine of patients on RDT was achieved by ion exchange chromatography and gel chromatography. Partially purified TNF‐BP reduced the growth inhibitory effect of rTNF on a susceptible leukemia cell line. TNF‐BP may act as a regulator of the biological activity of TNF and could have beneficial effects in certain inflammatory conditions.

Plasma Concentration Profiles of Simvastatin 3-Hydroxy-3-Methylglutaryl-Coenzyme A Reductase Inhibitory Activity in Kidney Transplant Recipients with and without Ciclosporin

A few cases of severe rhabdomyolysis have been reported in heart transplant recipients treated simultaneously with ciclosporin (CS) and the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor lovastatin. When measured, plasma lovastatin HMG-CoA reductase inhibitor concentrations in these patients were higher than expected. This prompted us to study the plasma concentration profiles of simvastatin HMG-CoA reductase inhibitory activity after a single dose of simvastatin in kidney transplant recipients. Five patients treated with CS, azathioprine and prednisolone (CS patients) were compared to 5 patients treated with azathioprine and prednisolone (non-CS patients). The concentration curves had similar shapes but the mean area under the curve/24 h was almost 3 times higher (p = 0.047) and the mean peak concentration was twice as high in CS patients (p = 0.028). These results suggest a difference in the disposition of simvastatin in CS patients as compared to non-CS patients. Simvastatin should be administered in a reduced dosage to CS patients.

Cytokines in childhood hemolytic uremic syndrome and thrombotic thrombocytopenic purpura

Serum and urine cytokines were analyzed in children with hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). Interleukin-6 (IL-6) was elevated in the serum of 33 of 35 children with HUS (94%) and in 2 of 2 children with recurrent TTP. Serum IL-6 was higher in children with HUS who developed anuria, extrarenal manifestations during the acute phase of illness and/or chronic renal sequelae. Tumor necrosis factor-α (TNF-α) was detected in the serum of 7 patients with HUS (20%) and 1 patient with TTP. IL-6 and TNF-α were elevated in the urine of 4 of 4 children with HUS and 2 of 2 children with TTP. Urinary levels were higher than serum levels, suggesting local production of cytokines in the urinary tract. Sequential serum and urine samples showed that IL-6 levels varied with disease activity. IL-6 and TNF-α were not detected in the serum (n=25) and urine (n=15) of healthy children. We conclude that IL-6 in urine may be used to monitor disease activity in HUS and TTP.

Stability of albumin, protein HC, immunoglobulin G, K- AND γ-chain immunoreactivity, orosomucoid and a 1-antitrypsin in urine stored at various conditions

Urine samples from 10 randomly selected patients with advanced renal disease were each divided into six aliquots and a preservative solution containing ben-zamidinium chloride, EDTA, tris(hydroxymethyl)-aminomethane and azide was then added to three of the aliquots. Aliquots with and without additive were then stored at room temperature for up to 7 days, at 4oC for up to 30 days and at -20 oC for up to 6 months. The concentrations of albumin, protein HC, IgG, orosomucoid and a 1-antitrypsin as well as the K- AND γ-chain immuno-reactivities in the samples were determined by automated immunoturbidimetry or by single radial immunodiffusion after 1, 3, 7, 14, 30, 90 and 180 days of storage. All investigated proteins, except α1-antitrypsin in native urine, were stable for 7 days in the samples stored at room temperature both in the presence and absence of additives. All investigated proteins, except a 1-antitrypsin in native urine, were stable for 30 days in the samples stored at 4oC both in the presence and a...

Analysis of proteinuria: reference limits for urine excretion of albumin, protein HC, immunoglobulin G, k- and Δ-immunoreactivity, orosomucoid and α1-antitrypsin

Efficient use of assessment of urine protein excretion in nephrological practice requires adequate reference intervals. To determine the upper reference limits of urine albumin, protein HC (α1-microglobulin), immunoglobulin G (IgG), orosomucoid (α1-acid glycoprotein), α1-antitrypsin, and k- and Δ-chain immunoreactivities, the concentrations of these proteins were measured in urine samples from 95 healthy, adult individuals, using rapid, generally available methods and with conditions for urine collection which secured stable protein levels. The obtained values were expressed inmgl−1, as the urine protein-creatinine index and as fractional protein-creatinine clearance.No differences were found between the upper reference limits in the first voided morning urine samples and the randomly collected urine samples, nor between the upper reference limits in urine samples collected from males and females. The urinary excretion of the tested proteins did not correlate to age, positive dipsticks for haematuria nor ...

Long-term Stability of Albumin, Protein HC, Immunoglobulin G, κ- and λ-chain-immunoreactivity, Orosomucoid and α1-antitrypsin in Urine Stored at -20°C

The stability of albumin, protein HC, immunoglobulin G, κ- and λ-chain immunoreactivity, orosomucoid and α1 -antitrypsin in urine stored at -20°C for up to 24 months was investigated. Significant decreases of the median concentration values for protein HC, IgG and α1-antitrypsin were observed for native urine. Addition to urine of a preservative solution containing benzamidinium chloride, EDTA, tris(hydroxymethyl)-aminomethane and azide prevented the decreases of the concentration values for protein HC and IgG but not for α1-antitrypsin. The median concentration values for albumin, orosomucoid and κ-and λ-chain immunoreactivity did not change significantly upon storage of native urine, nor for urine with the preservative solution.