Red-blood-cell transmembrane oxalate flux was measured in a group of patients with idiopathic calcium oxalate nephrolithiasis and in normal controls. The mean transmembrane oxalate flux rate was significantly higher in stone-forming patients than in controls (0·93±SD0·31/min vs 0·29±0·11/min). 80% of stone-forming patients showed raised (>2SD above the mean in controls) transmembrane oxalate flux. Anomalous cellular oxalate transport may be an important pathogenetic factor in calcium oxalate nephrolithiasis.

Morphological analysis of urinary red blood cells by phase-contrast microscopy to identify the source of bleeding was, and still is, widely used also as a starting point for workup. To evaluate the reliability of this approach, we studied 129 outpatients presenting with persistent isolated microhematuria; 31 subjects also had mild proteinuria (1 g/day), while 21 had pathological albumin levels. All patients were followed for a period of 6 years. During this time, 6 patients underwent renal biopsy for the onset of macrohematuria episodes and proteinuria of 2-3 g/day. Glomerular bleeding was identified in only 14.7% of the patients, despite the persistent microhematuria and the presence of proteinuria or microalbuminuria. The renal origin of the urinary erythrocytes correlated with histological findings in only 2 of 6 patients with dysmorphic erythrocytes who developed proteinuria (exceeding 1 g/day), and none with isomorphic erythrocytes showed urological abnormalities. These results challenge the validity and reliability of morphological analysis to identify the source of bleeding along the urinary tract.

We investigated patients affected by Bartter's syndrome in the attempt to localize the intracellular defect mediating the reduced intracellular Ca2+ mobilization that may be responsible for the decreased vascular reactivity characteristic of Bartter's syndrome. Using the formylmethionyl-leucyl-phenylalanine (fMLP) receptor system, which causes, intracellular calcium release, we investigated fMLP-stimulated intracellular inositol 1,4,5-trisphosphate (IP3) production as well as the number and affinity of fMLP receptors in neutrophils from Bartter's syndrome patients and healthy controls. Scatchard plot analysis of radioactive fMLP binding to neutrophils indicated that there were no differences in either cell receptor number and affinity for ligand between healthy controls (n = 5) and patients with Bartter's syndrome (n = 5): 6,151 +/- 1,431 vs. 7,112 +/- 2,566 receptors/cell; K(D): 0.446 +/- 0.14 vs. 0.454 +/- 0.09 pM of fMLP. 5- and 10-second fMLP-stimulated intracellular IP3 production was instead reduced in patients affected by Bartter's syndrome: 2.479 +/- 1.07 vs. 4.073 +/- 1.04 nmol/10(7) cells at 5 s (n = 8; p < 0.01); 1.673 +/- 0.741 vs. 3.766 +/- 1.348 nmol/10(7) cells at 10 s (n = 8; p < 0.005). The results of this study indicate that the anomaly of intracellular calcium mobilization in patients with Bartter's syndrome arises from a defect at the postreceptor level. The anomalous calcium signalling that takes place in Bartter's syndrome may provide a mechanism for the hyporesponsiveness to pressor stimuli characteristic of these patients.

A group od 129 patients with persistent asymptomatic microhematuria was studied for 7 years (1987-1994). At the beginning of the study, 31 patients showed mild proteinuria (less than 1 g/day) and in the rest of 98 patients, 21 showed microalbuminuria. At the end of the study none of the patients developed renal failure, urological disease, hypertension. Six patients out of 31 with mild proteinuria (less than 1 g/day), developed an increase of proteinuria over 2 and 3/day and underwent a renal biopsy while 2 out of 21 patients with altered microalbuminuria completely recovered after the follow-up period. The rest of 77 patients at the end of the study still showed isolated microhematuria. The results of this study support the hypothesis that in a population with age range between 16 and 28 years, the presence of persistent microhematuria, also associated with mild proteinuria, even for a long time, does not seem to lead to changes of renal function or to urological diseases.

Atherosclerotic complications are the leading cause of death in chronic renal failure (CRF) patients. Therefore, we wished to investigate the prevalence of carotid artery lesions (CALs) in these subjects. Two groups were evaluated by high-resolution echo Doppler: group 1 included 103 patients (68 males and 35 females) affected by nonnephrotic CRF and group 2 included 100 control subjects (60 males and 40 females). The prevalence of hypertension was 84% in both groups. The exclusion criteria included diabetes mellitus and symptoms of cerebrovascular disease. In the two groups we evaluated clinical history, physical examination, total cholesterol, triglycerides, fibrinogen, blood cell counts, blood urea nitrogen, creatinine, 24-hour proteinuria, and urine analysis. In group 1 patients the following lipid profile parameters were also evaluated: low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, lipoprotein(a), ApoAI, ApoAII, and ApoB. Group 1 had higher triglycerides and fibrinogen than group 2. A lower body mass index was found in group 1 than in group 2. The prevalence of CALs was significantly higher in the CRF patients than in the control subjects (62% v 47%; P = 0.04). The difference between the two groups was more striking among normotensive patients (62% v 19%; P = 0.03). All CRF patients affected by peripheral arterial disease and 86% of those having coronary artery disease had associated CALs. In CRF patients the severity of CALs was positively correlated to age, white blood cell count, triglycerides, and fibrinogen. Nondiabetic CRF patients have a higher prevalence of carotid artery lesions than control subjects. Several factors besides hypertension, including lipids, blood coagulation, and leukocytes, could contribute to the accelerated atherosclerosis of CRF patients.

Sixteen patients diagnosed with an aneurysm of abdominal aorta or Leriche disease underwent elective aortic surgery involving crossclamping of infrarenal aorta (ICC). These patients were randomized into two equal groups and 8 patients were infused with nifedipine starting from the isolation of aorta until the end of surgery (group A) while another 8 patients were infused with low-dose dopamine (group B) over the same surgical course. Plasma endothelin (ET) was measured before the induction of anesthesia, at the beginning and at the end of the clamp period and at the end of the operation. Intraoperatively, creatinine clearance and urinary excretion of PGE2, 6-keto PGF1 alpha and TxB2 were also determined before, during and after aortic crossclamping. Preoperative GFR as well as preinduction cardiac index (CI) and pulmonary capillary wedge pressure (PCWP) of the two groups did not differ. During cross-clamping plasma ET rose significantly in both groups. However, after clamp removal, plasma ET decreased in group A while it remained elevated in group B. Urinary excretion of TxB2, PGE2 and 6-keto PGF1 alpha increased during clamp in both groups, but the ratio of PGE2 + 6-keto PGF1 alpha/TxB2 during and after clamp was significantly higher in group A than in B. Postclamp creatinine clearance decreased in group B, and increased in group A; postoperative value of GFR was unchanged in group A and decreased significantly in group B. In conclusion, infusion of nifedipine, in contrast to dopamine, prevented the decrease of GFR in patients undergoing aortic surgery. This effect could be mediated by a nifedipine modulation of ET vascular synthesis and/or a preferential renal synthesis of vasodilating prostanoids.

Nitric oxide (NO) is a potent endogenous vasodilator and plays a pivotal role in the control of vascular tone by the formation of cyclic guanosine monophosphate (GMP). Patients affected by Bartter's syndrome have lower than normal vascular reactivity with normohypotension and decreased peripheral resistances in spite of biochemical and hormonal abnormalities typical of hypertension, and it is possible that increased production of NO may be involved in maintaining this reduced vascular response and vasodilatation. We have examined this possibility by studying NO2−/NO3− and cyclic GMP urinary excretions to assess NO production in vivo in seven patients affected by Bartter's syndrome compared with seven healthy controls. A group of five patients with hypokalemia other than Bartter syndrome (pseudo-Bartters) was also included in the study to evaluate the effect of hypokalemia on NO production. NO2−/NO3− urinary excretion (0.45 ± 0.14 v 0.25 ± 0.04 μmol/μmol urinary creatinine [controls], P < 0.005, v 0.28 ± 0.05 [pseudo-Bartters], P < 0.01) and cyclic GMP urinary excretion (0.057 ± 0.028 v 0.022 ± 0.01 μmol/μmol of urinary creatinine [controls], P < 0.009, v 0.024 ± 0.004 [pseudo-Bartters], P < 0.02) were increased in patients with Bartter's syndrome in comparison with controls and pseudo-Bartters, and a linear correlation between these two parameters was also present (P < 0.001). We conclude that in Bartter's syndrome the increased NO2−/NO3− and cyclic GMP urinary excretions point to an increased NO synthesis, which could account for the reduced vascular response of the disease, therefore adding its role in determining the vascular hyporeactivity of Bartter's syndrome.

The oxalate transport system along with protein phosphorylation appears to be deranged in stone formers. This study was undertaken to characterize in LLC-PK1 cells in culture the effect of altering specific intracellular second messenger systems on oxalate uptake. Cellular uptake experiments were performed at 37°C in buffer [265 mM mannitol, 5 mM NaOH, 5 mM KOH, 10 mM Ca-EGTA, 25 mM HEPES/TRIS, pH=7.4 or in Hank's balanced salt solution (HBSS)] containing 200 μM labeled oxalate (1-14C, 0.3 μCi). Cells were preincubated with DAG (final concentration of 100 μM), phorbol myristate acetate (10 μM), forskolin (50 μM), 8-bromo-cyclic AMP (50 μM), trifluoroperazine (20 μM) and low molecular weight heparin (1 mg/ml) for 10 min in the presence and absence of the anion transport inhibitor DIDS (100 μM) and the effect(s) on oxalate uptake at 10, 25 and 45 min incubation were determined. Chemicals (DAG, forskolin, TPA and 8-bromo-cAMP) which stimulate protein kinase A or C activity resulted in an increased uptake of oxalate while inhibitors of these systems (trifluoroperazine and low molecular weight heparin) resulted in decreased oxalate uptake. The results dernonstrate that oxalate uptake in renal tubular cells is modulated by protein kinase C and A dependent mechanisms.

An imbalance between endothelium-derived vasoactive substances such as endothelin and endothelium-derived nitric oxide (NO) might be viewed as a possible determinant of vascular hyporeactivity. To check this possibility the authors evaluated the role of endothelin and NO in the reduced vascular reactivity of Bartter's syndrome. Plasma immunoreactive endothelin (22.07 ±7.06 vs 13.80 ±1.43 pmol/L, P < 0.011), urinary excretion of NO 2 - (0.28 ±0.10 vs 0.15 ±0.02, μmol/μmol of urinary creatinine, P < 0.01) and NO3 - (0.17 ±0.07 vs 0.09 ±0.02 μmol/μmol of urinary crea tinine, P < 0.011), and forearm resting blood flow (FRBF) (6.67 ±1.69 vs 4.30 ±0.38 mL/m'/100 mL, P < 0.005) were increased in patients with Bartter's syndrome in comparison with normal controls (C). No difference in postischemic maximal FBF was found (34.14 ±4.67 vs 31.35 ±2.86 mL/minute/100 mL), while patients showed a slower recovery after peak flow (PF) (77.57 ±61.35 vs 9.42 ±3.69 seconds, P < 0.013). Higher plasma endothelin supports the defect in vascular reactivity of Bartter's syndrome already shown for angiotensin II and norepinephrine and is in keeping with the altered intracellular calcium signaling previously demonstrated by the authors in this syndrome. The increased excretion of NO2 - and NO3 - in this syndrome, together with the higher FRBF and the slower recovery of the FBF after PF, argues in favor of an increased NO synthesis in Bartter's syndrome and of assigning it a role in the vascular hyporeactivity of Bartter's syndrome.

Glycosaminoglycan administration has favourable effects on morphological and functional renal abnormalities in different models. The possibility that exogenous glycosaminoglycans modulate glomerular matrix synthesis was explored in both primary and SV40-MES13 murine mesangial cell cultures. On both cell types, both low-molecular-weight heparin and different glycosaminoglycans showed dose-dependent inhibition of proliferation and increase of (SO42-)-S-35 uptake. After 36 h the cell compartment contained a spectrum of S-35-molecules of less than 200 kDa; under heparin treatment, the two main (SO42-)-S-35 components (high and medium MW) increased by 16 and 37% respectively. Susceptibility to glycosidases revealed that heparin promotes the expression of heparan sulphate and increases that of chondroitin sulphate. Moreover, heparin modifies the expression of decorin and biglycan, involved in adhesion and fibrillogenesis, while not affecting perlecan. The extracellular matrix modulation in renal cells, for which the sulphation type and ratio of heparin are crucial, may thus explain the beneficial renal effects of heparin.

Ingestion of potassium salts typically induces both a kaliuresis and an increase in the systemic plasma potassium concentration. In this study normal healthy adults undergoing water diuresis ingested potassium citrate or sodium citrate (0.5 mmol/kg body weight) or continued without ion ingestion (a time control group). Urine was collected over 20-min intervals and venous blood sampled at midinterval. Intake of potassium citrate led to a significant increase in potassium excretion that began during the first postingestion collection and peaked 60-80 min after intake with a maximal increase in potassium excretion above baseline of 1.60 mumol/min.kg-1. The kaliuresis occurred without changes in plasma potassium concentration, excretion of creatinine or calcium, or urine hypo-osmolality and was associated with a briefer, smaller, and less regular increase in sodium excretion and a pronounced but irregular increase in chloride excretion. Plasma aldosterone was insignificantly elevated above baseline, and the initial increase did not occur until 40-60 min after potassium intake. Intake of sodium citrate did not produce a kaliuresis. The cause of the kaliuresis does not appear to be an increased systemic plasma potassium concentration, an increased plasma level of aldosterone, intake of citrate, or an elevated excretion of sodium. The mechanism inducing the kaliuresis following oral potassium intake in the absence of changes in systemic plasma potassium may involve a reflex initiated at potassium sensors in gut, portal vein, or liver.