Oxidative stress in gastric mucosa of asymptomatic humans infected with Helicobacter pylori: effect of bacterial eradication.

BACKGROUND: Inducible nitric oxide synthase (iNOS) and interleukin 8 (IL-8) are positive in approximately 50% of Helicobacter pylori-related diseases but it is not clear whether oxidative stress is also present in H. pylori asymptomatic humans. Our aim was to study the expression of iNOS, superoxide dismutase, catalase and IL-8 production in H. pylori-infected asymptomatic humans, and to investigate the effect of eradication of H. pylori. MATERIALS AND METHODS: Biopsies of corpus and antrum of asymptomatic H. pylori positive and negative humans served for determination of the gastritis score and H. pylori status; iNOS was measured by reverse transcriptase polymerase chain reaction and immunohistochemistry and superoxide dismutase and catalase by immunohistochemistry. IL-8 in biopsies was assessed by enzyme-linked immunosorbent assay. RESULTS: Immunostaining of iNOS, catalase and superoxide dismutase was significantly associated with H. pylori infection and was localized to inflammatory cells. IL-8 concentrations were greater in the H. pylori positive than H. pylori negative group and decreased after bacterial eradication. A decrease in staining for iNOS and catalase was observed after H. pylori eradication. CONCLUSIONS: INOS and antioxidant enzymes are present in gastric biopsies of asymptomatic H. pylori positive humans. Eradication caused a significant decrease in staining for iNOS and catalase. These results indicate that oxidative stress occurs in asymptomatic patients and can be modulated by H. pylori eradication.

[Self medication by the adolescent]. / Automédication chez l'adolescent.

To evaluate the extent and motivations of self-medication, a survey was conducted among 376 adolescents aged 15 to 20 using both written questionnaires and face-to-face interviews. 84% reported having taken some drug during the preceding 15 days, 57% on their own initiative. The most frequently cited drugs were analgesics, vitamins, homeopathy and anti-inflammatory drugs. Psychotropics had been taken by 7% (as self-medication by 3%). Street drugs, mainly cannabis derivatives, had been taken by 18%. The most usual indications for self-medication were headaches (42%), influenza-like syndromes (31%), school-related stress (21%), fatigue (19%) and mood concerns (15%). Most drugs were obtained from family reserves. A multivariate analysis showed self-medication to be associated with complaints regarding headaches, past drug dependency, concerns about illegal drugs or family interactions, recent respiratory illness, and diurnal somnolence. Self-medication increased with age. There was no relationship between self-medication and gender, citizenship, parental education level, or parental drug taking. Nor was self-medication related to knowledge about pharmaceuticals, assessed by specific questions. These results support the interpretation of self-medication mainly as a learned response to psychic/somatic ill-being. An optimal utility/risk ratio for self-prescribed drugs would require public health action and global involvement of practitioners.

Effects of uricosuric and antiuricosuric agents on urate transport in human brush-border membrane vesicles.

Inhibition of [14C]-urate uptake by uricosuric and antiuricosuric agents was investigated in human brush-border membrane vesicles, urate being transported either by anion exchange mechanisms or by voltage sensitive pathway. The IC50 for drugs on [14C]-urate uptake in vesicles loaded with 1 mM cold urate or with 5 mM lactate was, respectively: 0.7 and 0.3 microM for benzbromarone; 6 and 4 microM for salicylate; 133 and 13 microM for losartan; 520 and 190 microM for sulfinpyrazone and 807 and 150 microM, for probenecid. The IC50 ratio for [14C]-urate uptake in exchange for cold urate or for lactate varied from about 1 for salicylate to 10 for losartan, supporting the hypothesis that two distinct anion exchangers are involved in urate transport. Application of Hill equation revealed that urate/anion exchangers have more than one binding site, possibly two binding sites with high cooperativity, for benzbromarone and sulfinpyrazone, but only one for probenecid, salicylate and losartan. The uricosuric diuretic, tienilic acid was 10 to 50 times more potent than hydrochlorothiazide, chlorothiazide and furosemide, for inhibiting [14C]-urate uptake in exchange for cold urate. This higher potency is the reason of its uricosuric properties. All uricosuric agents, as well as the antiuricosuric agents, pyrazinoate and ethambutol, had a much lower potency for inhibiting [14C]-urate uptake through the voltage sensitive pathway (apical secretory step) than through the urate/anion exchangers. This suggests that antiuricosuria, induced by pyrazinoate and ethambutol, as well as by low concentrations of uricosuric agents, does not result from an inhibition of the apical voltage sensitive pathway.

Determination of trace lithium in biological fluids using graphite furnace atomic absorption spectrophotometry: variability of urine matrices circumvented by cation exchange solid phase extraction.

A graphite furnace atomic absorption spectrometry method has been developed for the quantitative determination of submicromolar endogenous concentration of lithium in human plasma and urine using pyrolitically-coated graphite tubes in combination with ammonium nitrate matrix modification. This latter treatment could not completely abolish the interferences caused by the matrix, notably in urine samples. The variability of the urinary matrices required an additional standardization procedure by solid-phase extraction on strongly acidic cation exchange cartridges. Matrix-matched samples were used for the establishment of calibration curves with the addition-calibration method. Calibration curves were linear up to 0.72 mumol/l (1.0 > r2 > 0.99). The described method enables accurate measurements of trace-lithium in biological samples at concentrations down to 0.03 mumol/l with intra- and inter-day variabilities < 10%. The method was applied to the determination of trace-lithium levels in urine and plasma samples from healthy individuals enabling the calculation of its fractional excretion (FeLi) (median range 17.3%), a value which reflects the functional capacity of the kidney to reabsorb sodium and water at the proximal tubular portion of the nephron. This sensitive method can thus be used as an investigative and diagnostic tool in various renal pathophysiological conditions, in clinical research, and may also be applied to studies on the trace-lithium status of population in connection with psycho-affective disorders.

Effects of neuropeptide Y on intrarenal hemodynamics, plasma renin activity and urinary sodium excretion in rats.

Neuropeptide Y (NPY) is a vasoconstrictor peptide possibly involved in the regulation of renal sodium handling and renin release. This investigation was undertaken to assess in conscious normotensive rats the acute effects of a non-pressor dose of NPY on renal plasma flow, glomerular filtration rate, sodium excretion and plasma renin activity. Experiments were also performed during concomitant beta-adrenoceptor stimulation with isoproterenol. NPY per se had no effect on the studied parameters. Renal plasma flow was increased by isoproterenol and was significantly higher when the beta-adrenoceptor stimulant was infused alone (13.4 +/- 2.1 ml/min, p < 0.05, mean +/- SEM) that when administered together with NPY (7.2 +/- 2.0 ml/min). This was also true for glomerular filtration rate (3.3 +/- 0.3 vs. 1.8 +/- 0.3 ml/min, p < 0.01) and plasma renin activity (6.3 +/- 1.7 vs. 2.1 +/- 0.4 ng Ang I/ml/h, p < 0.05). Our data however do not allow to deduce whether the inhibitory effect of NPY on isoproterenol-induced renin release is mediated by changes in intrarenal hemodynamics or a direct effect on juxtaglomerular cells.

Fractional excretion of trace lithium and uric acid in acute renal failure.

The early distinction between prerenal azotemia, characterized by an avid proximal tubular sodium reabsorption, and ATN, in which proximal tubule function is depressed, remains an important but difficult clinical task. Indices of acute renal failure based on urinary sodium excretion may be helpful but have several limitations, among which is the use of diuretics. The effectiveness of the fractional excretion of uric acid (FEUA) and that of endogenous lithium (FELi) in the diagnosis of acute renal failure has been evaluated in an unselected group of 46 patients, 28 with prerenal azotemia and 18 with ATN. In the entire group, FELi concurred with the clinical diagnosis in 78% of the patients, whereas the fractional excretion of sodium (FENa) and FEUA were in agreement in only 63 and 50%, respectively. FELi was more sensitive to identify hemodynamic renal failure, because 93% of prerenal failure patients had a low FELi, contrasting with a low FEUA in only 68% and a low FENa in 75%. The major reason for the discrepancy between FENa and FELi was the administration of diuretics. In both acute renal failure groups, FENa was higher in the subgroups receiving diuretics. In contrast, diuretic therapy had no effect on FELi in either group. These results suggest that FELi is more accurate than either FENa or FEUA for distinguishing prerenal azotemia from ATN. The superiority of FELi appears especially relevant in patients treated with the usual diuretics.

Cadmium uptake by brush border membrane vesicles from the rabbit renal external cortex.

Brush border membrane vesicles (BBMV) isolated from the rabbit renal external cortex were used to investigate inorganic cadmium (Cd) uptake. BBMV were incubated during 1 to 60 min in a buffered solution containing 10 to 200 mumol/L Cd (CdCl2), and uptake was determined using a rapid filtration technique. Cd uptake by BBMV was time-and concentration-dependent. At the lowest concentration (10 mumol/L), Cd uptake was nearly complete (70% of the plateau value, which was obtained after 10 min) within 1 min. At the highest concentration (200 mumol/L), the percentage of Cd uptake during the first minute was smaller (50%) and a slower component of uptake appeared. From additional experiments where Cd-loaded BBMV were submitted to an osmotic shock or to variations of extravesicular osmolality, it was concluded that the uptake of Cd by BBMV resulted essentially from membrane binding and not from intravesicular accumulation. The change in pH from 7.4 to 5.8 under iso- or hypotonic conditions removed about 40% of Cd bound to the BBMV, indicating that Cd binding to the membrane is pH sensitive. Thus, binding to the brush border membrane constitutes an initial step for inorganic Cd entry into renal epithelial cells.

Dietary calcium restriction enhances cadmium-induced metallothionein synthesis in rats.

Experiments were conducted with adult male rats to investigate the effects of dietary calcium (Ca) restriction upon intake and tissue distribution of cadmium (Cd), and Cd-metallothionein (Mt) synthesis. Four groups of animals were fed either a low-Ca, semisynthetic diet (0.1% Ca) or the same diet supplemented with 0.8% Ca (normal diet). The caloric intake was similar in all groups. Two groups (low-Ca and normal diet) were used as controls, and two groups (low-Ca and normal diet) received 100 mg/l Cd (as CdCl2) in drinking water. Cd levels in liver, kidney, spleen and red cells were measured in all animals after 8 weeks of treatment. Concomitantly, Mt levels in plasma, liver and kidney were evaluated by radioimmunoassay. Ca deficiency entailed marked and significant increases in accumulation of Cd and synthesis of Mt in all assayed tissues. It is concluded that dietary Ca restriction, independent of caloric intake, enhances Cd intestinal absorption and tissue accumulation, which is followed by increased tissue Mt synthesis.

Cadmium uptake and induction of metallothionein synthesis in a renal epithelial cell line (LLC-PK1).

LLC-PK1 cells, an established cell line from pig kidney with proximal tubule properties, were cultivated in vitro at confluence on plastic dishes. They were then exposed (apical side) to inorganic cadmium (CdCl2, 5 microM) for periods ranging between 1 to 24 h. Analysis of the cell supernatant after homogenisation and ultracentrifugation indicated that Cd taken up in the first 3 h was bound to cytosolic high molecular weight proteins, but was redistributed to low molecular weight proteins at later stages. Induction of Cd-metallothionein (Cd-Mt) synthesis, as judged from Cd-Mt binding to a specific anti-Cd-Mt antibody and from the rate of 35S-cys incorporation into a specific protein fraction, was apparent 3-6 h after the addition of Cd to the incubation medium.

Fate of cadmium in rat renal tubules: a micropuncture study.

Free-flow micropuncture was carried out in superficial nephrons of Munich-Wistar type rats infused acutely with Cd acetate (CdA) or Cd-DTPA (141 microM Cd). Fluid obtained from Bowman's space (BS) or end-proximal tubule sites was analyzed for Cd and inulin. The fluid/plasma Cd concentration ratio in BS averaged 0.2 and 1.0 during CdA and Cd-DTPA infusions, respectively. End-proximal tubule fractional excretion of Cd during CdA infusion averaged 0.34. Previous administration of CdA (1.0 mg/kg, 48 hr before micropuncture) increased the level of circulating Cd-metallothioneins, as measured by radioimmunoassay, but did not affect the luminal tubular uptake of Cd during CdA infusion. No net transepithelial movement of Cd-DTPA was measured. It is concluded that Cd ultrafiltered during inorganic Cd administration is taken up to a large extent by the convoluted part of proximal tubules.

Fate of cadmium in rat renal tubules: a microinjection study.

109Cd was injected into the lumen of superficial proximal or distal tubules of rat kidneys, and recovery in the pelvic urine from the ipsilateral kidney was measured. Fractional recovery of labeled inulin always exceeded 90%. About 70% of injected inorganic Cd (CdCl2) was taken up by the epithelium of proximal tubules, while more than 90% of the injected amount was recovered after distal microinjection. The proximal fractional Cd uptake of a 1:1 (molar) Cd-L-cysteine complex was 82%, but was below 60% for a 5-10:1 molar ratio of cysteine:Cd. The chelate Cd-pentetic acid was recovered in final urine nearly quantitatively after proximal or distal microinjection. Fractional uptake of 109Cd from a Cd-metallothionein (Mt) complex, following proximal microinjection, ranged between 17 (Cd-Mt 0.19 mM) and 8% (Cd-Mt 1.5 mM). It is concluded that luminal Cd uptake by the tubular epithelium depends markedly on the chemical form of Cd and, when present, occurs mostly or exclusively in proximal tubules.

Site of the action of a synthetic atrial natriuretic peptide evaluated in humans.

The renal site of the natriuretic effect of human, atrial natriuretic peptide (hANP) was studied using clearance techniques in eight salt-loaded normal volunteers undergoing maximal water diuresis. Lithium was used as a marker of proximal sodium reabsorption. According to a two-way, single blind, crossover design, hANP (Met12-(3-28)-eicosahexapeptide, (2 micrograms/min) or its vehicle (Ve) were infused for two hours, followed by a two-hour recovery period. Blood pressure, heart rate and insulin clearance remained unchanged. During hANP infusion, the filtration fraction increased slightly from 19.6 to 24.3% (P less than 0.001), fractional water excretion rose transiently at the beginning of the infusion. Fractional excretion of sodium increased markedly from 2.2% to 7.4% (P less than 0.001) but remained unchanged with Ve. ANP increased fractional excretion of lithium slightly from 46 to 58% (P less than 0.01), while it remained stable at 47% during Ve. The distal tubular rejection fraction of sodium calculated from sodium and lithium clearances rose markedly from 4.7 to 13% (P less than 0.001) and returned to 6.2% at the end of the recovery period. Thus, under salt loading and water diuresis conditions, hANP infusion did not alter GFR, but reduced proximal reabsorption of sodium, and markedly enhanced the fraction of sodium escaping distal tubular reabsorption, suggesting that hANP-induced natriuresis is due, for an important part, to inhibition of sodium reabsorption in the distal nephron.

Lithium infusion to study sodium handling in unanesthetized hypertensive rats.

To investigate renal tubular handling of sodium in various types of experimental hypertension, sodium, lithium, and inulin clearances were measured simultaneously in unanesthetized rats. Fractional excretion of lithium was used as an index of proximal sodium reabsorption. Eight groups of animals, all of the Wistar-Kyoto strain, were studied. Three were hypertensive: spontaneously hypertensive rats (SHR), rats with two-kidney, one clip renal hypertension, and uninephrectomized rats with deoxycorticosterone-salt hypertension. The five normotensive control groups included animals given normal, low, or high dietary sodium loads and rats with reduced renal mass. Fractional excretion of lithium was not influenced by moderate changes of glomerular filtration rate, but was sharply enhanced by sodium loading. Increased blood pressure was associated with enhanced urinary sodium excretion in uninephrectomized deoxycorticosterone-salt hypertensive and two-kidney, one clip hypertensive rats, as a result of decreased distal tubular reabsorption ("pressure natriuresis"). In contrast, SHR showed reduced sodium excretion and decreased fractional excretion of lithium, which suggests that increased sodium reabsorption in the proximal tubule may contribute significantly to the maintenance of hypertension.

Inhibition of aldosterone-induced antinatriuresis and kaliuresis by actinomycin D.

The effects of actinomycin D on short-term response to aldosterone on sodium and potassium urinary excretion were investigated in adrenalectomized glucocorticoid-substituted anesthetized rats. Aldosterone alone (1 microgram/kg followed by sustained intravenous infusion of 1 microgram X kg-1 X h-1) entailed a simultaneous antinatriuretic and kaliuretic effect after a latent period of 30-60 min. Actinomycin D (300 micrograms/kg) administered intravenously 30 min before aldosterone inhibited both the aldosterone-induced kaliuresis and antinatriuresis and the concomitant changes in plasma potassium concentration. The administration of actinomycin D alone enhanced sodium excretion in the first hour and then induced kaliuresis. These results favor the hypothesis that mineralocorticoid effects of aldosterone on sodium and potassium excretion are closely linked and may be dependent on the same mechanisms.

Renal handling of cadmium: a study by tubular microinjections.

109Cadmium was microinjected, in different chemical forms, into the proximal or distal cortical tubules of adult rats and recovery in the pelvic urine from the ipsilateral kidney was measured. There was marked uptake of inorganic cadmium along the proximal tubules, and only negligible uptake in the distal nephron. The fractional uptake of the complex cadmium-cysteine in the proximal tubule was inversely related to the cysteine concentration. The chelate cadmium-pentetic acid was completely recovered in the pelvic urine.

Effect of aldosterone on the excretion of lithium in the adrenalectomized rat.

The effect of aldosterone (1 microgram/kg X h) on the urinary excretion of lithium (Li) was measured by clearance studies in adrenalectomized rats receiving a glucocorticoid substitution (dexamethasone 6.6 micrograms/kg). Aldosterone induced significant anti-natriuresis and kaliuresis. The fractional excretion of Li remained constant around 28% and was not modified by aldosterone during the experiment (4 h). These results indicate that the tubular reabsorption of Li is not directly dependent on mineralocorticoid hormones. The previously reported effects of long term administration of DOCA or spironolactone of Li excretion are probably secondary to modifications of the sodium balance which, in turn, influences the proximal Li reabsorption rate.

Effects of mineralocorticoids on Na+ and K+ excretion in the adrenalectomized rat.

The short-term effects (within 4 h) of low doses of intravenous aldosterone or deoxycorticosterone on potassium and sodium urinary excretion were studied by clearance techniques in 24-h adrenalectomized, anesthetized male rats. All animals were substituted with a glucocorticoid (dexamethasone; plasma concentration approximately 6 nM) to maintain normal glomerular filtration rate. The mineralocorticoid effects were studied under various conditions of sodium and potassium load. Mineralocorticoid administration uniformly resulted in antinatriuresis, starting within 30-60 min and, at the peak effect, amounting to 1-2% sodium fractional excretion. The level of antinatriuresis was directly related to the control sodium excretion before aldosterone administration. Mineralocorticoids induced a significant kaliuresis in all groups except one, the one receiving the lowest sodium load. The aldosterone-induced kaliuresis was also related to the sodium load and the control fractional sodium excretion level and was simultaneous with the beginning of the reduced sodium excretion. In control, mineralocorticoid-deprived rats, kaliuresis was not enhanced by increasing the sodium load. Control as well as mineralocorticoid-treated rats responded by an increased kaliuresis following an acute potassium load and by a decreased kaliuresis after 3 days of low potassium diet.

[Acute kidney failure due to drugs or toxic substances]. / Insuffisance rénale aiguë d'origine médicamenteuse ou toxique.

The main causes and mechanisms of acute renal failure due to drugs and other chemicals are briefly reviewed. In clinical settings, aminoglycoside antibiotics appear to be the drugs most commonly involved in acute toxic kidney diseases. Beta-lactam antibiotics have been most commonly associated with acute tubulo-interstitial lesions, which are thought to be due to immunological mechanisms. The important role of risk factors in toxic nephropathies is stressed.