Sex Differences in Renal Proximal Tubular Cell Homeostasis.

Studies in human patients and animals have revealed sex-specific differences in susceptibility to renal diseases. Because actions of female sex hormones on normal renal tissue might protect against damage, we searched for potential influences of the female hormone cycle on basic renal functions by studying excretion of urinary marker proteins in healthy human probands. We collected second morning spot urine samples of unmedicated naturally ovulating women, postmenopausal women, and men daily and determined urinary excretion of the renal tubular enzymes fructose-1,6-bisphosphatase and glutathione-S-transferase-α Additionally, we quantified urinary excretion of blood plasma proteins α1-microglobulin, albumin, and IgG. Naturally cycling women showed prominent peaks in the temporal pattern of urinary fructose-1,6-bisphosphatase and glutathione-S-transferase-α release exclusively within 7 days after ovulation or onset of menses. In contrast, postmenopausal women and men showed consistently low levels of urinary fructose-1,6-bisphosphatase excretion over comparable periods. We did not detect changes in urinary α1-microglobulin, albumin, or IgG excretion. Results of this study indicate that proximal tubular tissue architecture, representing a nonreproductive organ-derived epithelium, undergoes periodical adaptations phased by the female reproductive hormone cycle. The temporally delimited higher rate of enzymuria in ovulating women might be a sign of recurring increases of tubular cell turnover that potentially provide enhanced repair capacity and thus, higher resistance to renal damage.

Stabilizing the urinary activity of fructose-1,6-bisphosphatase with EDTA and mercaptoethanol.

OBJECTIVES: The study aim was to establish conditions for stabilization the activity of fructose-1,6-bisphosphatase (FBP-1) in stored urine. DESIGN AND METHODS: The FBP-1 was determined by the method Kepka et. al in a collected fraction of purified urine. RESULTS: EDTA and mercaptoethanol stabilized FBP-1 activity in stored urine. CONCLUSION: At optimal conditions urine may be stored up to 7 days at a temperature of 4 degrees C.

Urinary fructose-1,6-bisphosphatase activity as a marker of the damage to the renal proximal tubules in children with idiopathic nephrotic syndrome.

BACKGROUND: Disturbances in the function of renal proximal tubules increase the activity of several enzymes in urine. Among them is fructose-1,6-bisphosphatase (FBP-1), the key enzyme of gluconeogenesis normally present in the renal convoluted, and to smaller degree, proximal renal tubular cells cytosol. FBP-1 activity in urine and serum was used for evaluation of the degree of graft ischemia during human kidney transplantation. The aim of our present research was to determine FBP-1 activity in urine as an indicator of damage to renal proximal tubules in children with idiopathic nephrotic syndrome (INS). METHODS: We evaluated the excretion of FBP-1 into urine of 21 children (10 girls and 11 boys) with INS, aged from 10 to 15 years and 30 healthy children (14 girls and 16 boys), aged from 2 to 15 years. FBP-1 activity was determined by the Latzko and Gibbs method. Creatinine (mg%) in urine and blood serum was measured by the Jaffe method in Larsen modification. Protein in blood serum was determined by the biuret method (g/L), and albumin (mg%) by the Young method. Proteinuria in the urine collected over 24 h was measured with the Exton turbidimetric method by Tomaszewski with modification and expressed in mg/kg body weight/24 h. RESULTS: In the urine of 30 healthy children, FBP-1 activity was in the range from 0-1.74 micromol FPB/h/mmol of creatinine. In 43% of the healthy children, FBP-1 activity in urine was not detectable. In the period of intensive proteinuria during the INS in children, FBP-1 activity and protein concentrations in urine were significantly higher than in the control group (p<0.0008 and p<0.0001, respectively). In the urine of children with active INS, we observed a very weak negative linear correlation between protein concentration and FBP-1 activity (r=-0.5018, p=0.067). After treatment with Encorton (prednisone), FBP-1 activity and protein concentration in urine dropped to values of the control group. CONCLUSIONS: "The overload" of proximal renal tubules by proteins in children with INS releases FBP-1 into urine. FBP-1 activity in urine may therefore be considered as a marker of damage to the proximal renal tubules in children with INS.

[Fructose-1,6-bisphosphatase--marker of damage to proximal renal tubules]. / Fruktozo-1,6-bisfosfataza--marker uszkodzenia cewek nerkowych blizszych.

Pathological processes disturbing function of renal proximal tubules, increase activity of fructose-1,6-bisphosphatase (FBP-1) in urine. FBP-1 is cytosolic enzyme which occured mainly in cells of proximal renal tubules, and to small extent in cells of pars recta. After damage to the cell membrane FBP-1 is more rapidly excreted to the urine, than enzymes residing in other cell organelles. Fructose-1,6-bisphosphatase was isolated from rabbit muscle in 1943 by Gomori, and from spinach in 1958 by Racker i Schröder. Highest activity of FBP-1 was found in liver and kidneys, lesser in ileum, leucocytes, muscles and brain. Fructose-1,6-bisphosphatase is one of four key enzymes of gluconeogenesis performing synthesis of glucose from non sugar substrates. FBP-1 catalyses hydrolysis of fructose-1,6-bisphosphate in cytoplasm of the cell. There are many reports on properties and significance of FBP-1 in plant and animal tissues, but only few reports on activity of this enzyme in urine. Reason for little interest in determination of FBP-1 activity in urine, is relative instability of this enzyme in urine.

[Assessment of fructose-1,6-biphosphatase in urine of children with acute pyelonephritis]. / Ocena aktywnosci fruktozo-1,6 dwufosfatazy w moczu dzieci chorych na ostre odmiedniczkowe zapalenie nerek.

UNLABELLED: We assessed the excretion of fructose-1,6-bisphosphatase (FBP) and N-acetyl-beta-D-glucosaminidase (NAG) in 52 children (aged 4.1 +/- 2.3): group I--26 children with acute pyelonephritis (APN), in whom the examination were carried out twice: A--before treatment, B--after 14-21 days of antibacterial treatment, group II--21 healthy children. Activity of FBP in urine was found in 80% children from group I and II, and activity of NAG was found in all children from both groups. In examination A mean excretion of FBP and NAG was higher than in healthy children (p < 0.05). After antibacterial treatment excretion of both enzymes decreased to values, which did not differ from control group (p > 0.05). High correlation between FBP and NAG (r = 0.9355; p = 0.00001) was shown only in 14 children, in whom the course of acute pyelonephritis was serious (CRP > 20 mg%, leucocytosis > 10 x 10(9), and renal swelling in ultrasonography). CONCLUSION: Increased excretion of FBP in urine is found mainly in children with severe course of acute pyelonephritis, in whom the correlation between NAG and FBP is observed.

Rapid, simplified and sensitive method for screening fructose-1,6-diphosphatase deficiency by analyzing urinary metabolites in urease/direct preparations and gas chromatography-mass spectrometry in the selected-ion monitoring mode.

Children with fructose-1,6-diphosphatase (FDPase) deficiency often experience life threatening episodes such as ketotic hypoglycemia. We report here a rapid, simplified and sensitive method to analyze glycerol-3-phosphate (G3P) and glycerol in urine, that can be used to detect FDPase deficiency. We used the urease/direct preparation and gas chromatography-mass spectrometry in the selected-ion monitoring mode, enabling detection of G3P and glycerol level in normal controls. Using this approach, FDPase deficiency can be more easily diagnosed and differentiated from glycerol kinase deficiency or glycerol infusion patients. To date, diagnosis has been essentially based on the assay of enzymes in the liver. The proposed non-invasive method provides a clinically significant diagnostic tool that may help prevent episodic attacks.

Graft ischemia correlates with urinary excretion of the proximal marker enzyme fructose-1,6-bisphosphatase in human kidney transplantation.

This study was undertaken to test the hypothesis that ischemia prior to transplantation causes tubular damage without clinical evidence of graft dysfunction. The urinary excretion of fructose-1,6-bisphosphatase (EC 3.1.3.11, FBPase), a cytosolic enzyme located exclusively in the proximal tubules, and the lysosomal enzyme N-acetyl-beta-D-glucosaminidase (EC 3.2.1.30) were measured daily between postoperative days 1 and 4 in 25 renal cadaveric graft recipients who enjoyed an entirely uncomplicated first postoperative month. During the first 4 posttransplant days urinary FBPase excretion was 0.9 +/- 0.5 U/g (0.1 +/- 0.06 U/mmol) urinary creatinine [+/-SD; range 0.2-2.1 U/g (0.02-0.24 U/mmol)]. Cold ischemia time was 20.6 +/- 8.4 h (median 22 h, range: 3-32 h). Multiple regression revealed a significant correlation between cold ischemia time and posttransplant urinary FBPase excretion (multiple R = 0.65, p < 0.001). There were no confounding effects of recipient's age and gender, number of previous transplants, cyclosporin A levels, warm ischemia time, anastomosis time, donor age and gender. Urinary FBPase excretion was significantly lower in grafts stored for a shorter time than the median cold ischemia time of 22 hours (0.69 +/- 0.42 U/g, n = 13) as compared to those stored for a longer period of time (1.13 +/- 0.56 U/g; n = 12; p = 0.035). These results indicate that graft injuries occur even in the absence of graft dysfunction and that the duration of cold ischemia itself correlates with a degree of tubular cell damage as defined by urinary FBPase excretion.

Clinical value of fructose 1,6 bisphosphatase in monitoring renal proximal tubular injury.

The usefulness of the gluconeogenic key enzyme fructose 1,6 bisphosphatase (FBPase), which is localized exclusively in the proximal nephron segment, as a marker compound to monitor injury of the proximal nephron segment during nephrotoxic therapy, was tested in a collective model of male patients treated for testicular cancer. These patients with normal kidney function were submitted to therapy with the nephrotoxic chemotherapeutics carboplatinum and a combination of cisplatinum, etoposide, bleomycin and ifosfamide. The release of FBPase activities into the urine was monitored during the initial two treatments over a period of eight days. The urinary enzyme activities measured were compared to the excretion of the "proximal tubular injury markers" N-acetyl-beta-D-glucosaminidase (NAG) and alpha 1-microglobulin (alpha 1m). The presence of glomerular damage was determined by measurement of urinary excretion rates of albumin (ALB) and IgG. In addition, protein excretion patterns following chemotherapy were monitored. The combined administration of cisplatin, etoposide and ifosfamide resulted in a pronounced proximal tubular injury as shown by the release of FBPase into the urine. This is substantiated by simultaneously increased excretion rates for NAG and alpha 1m. Proximal tubular toxicity was found to be less severe when cisplatin was combined with etoposide and bleomycin and was nearly absent following carboplatinum monotherapy. Carboplatinum only affected glomerular function and resulted in an elevated ALB and IgG excretion. From this model investigation it can be delineated that determination of urinary FBPase activities ensures a sensitive and reliable identification of proximal nephron damage.

Urinary enzyme analysis in renal allograft transplantation.

The urinary excretion of four enzymes (fructose-1,6-bisphosphatase, glutathione S-transferase, N-acetyl-beta-D-glucosaminidase and pyruvate kinase) was assayed daily in 59 patients following renal cadaveric allografting. 51 patients were given cyclosporin A (CyA group) as an immunosuppressive, 8 patients were treated conventionally with azathioprine and prednisolone (CON-group). Urinary enzyme output was evaluated by two different mathematical models. Model A follows single enzyme excretion, whereas model B also analyzes enzyme patterns. The best results were obtained by a combined analysis of all four enzymes with model B. In the CON-group the sensitivity was 1.00, the specificity 0.85, the predictive values of positive test 0.45 and all 12 graft rejections were diagnosed correctly. In the CyA group the sensitivity was 0.40, the specificity 0.99, the predictive value of positive test 0.33, and 6 out of 9 rejections were recognized. The evaluation of the single enzymes did not produce similarly good results with either model.

[Urinary enzymes in the non-invasive diagnosis of kidney epithelial lesions in acute kidney failure]. / Harnenzyme zur nichtinvasiven Diagnostik von Nierenepithelschäden im akuten Nierenversagen.

The present investigation describes the urinary output of four different enzymes localized within nephron cells in two models of experimental acute renal failure. The activities of fructose-1,6-diphosphatase (FDP), glutathione-S-transferase (GST), N-acetyl-beta-D-glucosaminidase (NAG) and pyruvate kinase (PK) were determined in the urine of rats after maleate or HgCl2 intoxication. 2 hours after maleate intoxication the urinary output of FDP, GST and NAG was significantly increased above control values. 6 hours after HgCl2 poisoning FDP, GST and NAG showed increased urinary enzyme activities. The urinary activity of each enzyme was significantly increased 24 hours after intoxication. These results are in good accordance with the damage observed on light and electron microscopic investigations carried out with both experimental models. Furthermore, general problems of urinary enzyme measurements are discussed in this paper.