Critical study of the value of renal clearances measured by the single shot technic

A critical approach to the problem of establishing new methods of measurement of kidney function is presented. Variability of the reference clearances inulin and PAH is large, thus reference method ratios close to 1 are not sufficient to ascertain the value of the method under investigation. EDTA 51Cr and hippuran 125I, single shot technics illustrate the need for more accurate criteria required for validating a new technic.

Inhibition of SRC corrects GM-CSF hypersensitivity that underlies juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is an aggressive myeloproliferative neoplasm in children characterized by the overproduction of monocytic cells that infiltrate the spleen, lung, and liver. JMML remains a disease for which few curative therapies are available other than myeloablative hematopoietic stem cell transplant (HSCT); however, relapse remains a major cause of treatment failure and the long-term morbidities of HSCT for survivors are substantial. A hallmark feature of JMML is acquired hypersensitivity by clonal myeloid progenitor cells to granulocyte macrophage-colony stimulating factor (GM-CSF) via a largely unknown mechanism. Here, we identify c-Cbl (henceforth referred to as Cbl) as a GM-CSF receptor (GMR) adaptor protein that targets Src for ubiquitin-mediated destruction upon GM-CSF stimulation and show that a loss of negative regulation of Src is pivotal in the hyperactivation of GMR signaling in Cbl-mutated JMML cells. Notably, dasatinib, an U.S. Food and Drug Administration-approved multikinase inhibitor that also targets Src family, dramatically attenuated the spontaneous and GM-CSF-induced hypersensitive growth phenotype of mononuclear cells from peripheral blood and bone marrow collected from JMML patients harboring Cbl or other known JMML-associated mutations. These findings reveal Src kinase as a critical oncogenic driver underlying JMML.

[How to assess the impact of morbimortality conferences on healthcare quality and safety in ICU ?]

OBJECTIVE

To estimate the morbidity and mortality conferences (MMC) impact in intensive care unit (ICU) setting on quality of care and patients' safety.

DATA SOURCES

A review of English and French articles in Medline database (1990-2011) related to MMC in the ICU. Keywords used: "morbidity (and) mortality conference(s)", "intensive care unit", "intensive/critical care medicine". Additional studies identified by hand search in French national guidelines about MMCs and in the Annales Françaises d'Anesthésie Réanimation and Réanimation journals index. Identification and preliminary analysis performed using title and abstract, for every study related to MMC in the ICU.

STUDY SELECTION

Only original studies about MMC in the ICU setting that reported an assessment were included. Papers reporting guidelines and methods for MMC implementation were excluded.

DATA EXTRACTION

Extraction used predefined data fields, including study design, MMC characteristics, assessment methods and results.

DATA SYNTHESIS

Studies about MMC in the ICU are recent and scarce. Results comparison and synthesis are impaired by discrepancies in study designs. Although the effectiveness of MMC is not evidence-based, data are consistent for their positive impact on quality of care and patient safety in the ICU.

CONCLUSION

Further studies are required to assess the impact of MMC in the ICU. Based on this literature review, a 4-level evaluation scheme can be suggested: 1) evaluation of MMC implementation in care units and facilities; 2) evaluation of MMC organization; 3) evaluation of MMC on quality of care; 4) evaluation of MMC impact on patients' mortality and morbidity.

Identification, characterization and rescue of a novel vasopressin-2 receptor mutation causing nephrogenic diabetes insipidus

OBJECTIVE

X-linked nephrogenic diabetes insipidus (XNDI), caused by mutations in the V2 vasopressin receptor (V2R), is clinically distinguished from central diabetes insipidus (CDI) by elevated serum vasopressin (AVP) levels and unresponsiveness to 1-desamino-8-d-arginine vasopressin (DDAVP). We report two infants with XNDI, and present the characterization and functional rescue of a novel V2R mutation.

PATIENTS

Two male infants presented with poor growth and hypernatraemia. Both patients had measurable pretreatment serum AVP and polyuria that did not respond to DDAVP, suggesting NDI. However, both also had absent posterior pituitary bright spot on MRI, which is a finding more typical of CDI.

METHODS

The AVPR2 gene encoding V2R was sequenced. The identified novel missense mutation was re-created by site-directed mutagenesis and expressed in HEK293 cells. V2R activity was assessed by the ability of transfected cells to produce cAMP in response to stimulation with DDAVP. Membrane localization of V2R was assessed by fluorescence microscopy.

RESULTS

Patient 1 had a deletion of AVPR2; patient 2 had the novel mutation L57R. In transiently transfected HEK293 cells, DDAVP induced detectable but severely impaired L57R V2R activity compared to cells expressing wild-type V2R. Fluorescence microscopy showed that myc-tagged wild-type V2R localized to the cell membrane while L57R V2R remained intracellular. A nonpeptide V2R chaperone, SR121463, partially rescued L57R V2R function by allowing it to reach the cell membrane.

CONCLUSIONS

L57R V2R has impaired in vitro activity that can be partially improved by treatment with a V2R chaperone. The posterior pituitary hyperintensity may be absent in infants with XNDI.

A conserved lysine in the estrogen receptor DNA binding domain regulates ligand activation profiles at AP-1 sites, possibly by controlling interactions with a modulating repressor

Background

Estrogen receptors alpha and beta (ERα and ERβ) differentially activate genes with AP-1 elements. ERα activates AP-1 targets via activation functions with estrogens (the AF-dependent pathway), whereas ERβ, and a short version of ERα (ERα DBD-LBD) activate only with anti-estrogens (AF-independent pathway). The DNA binding domain (DBD) plays an important role in both pathways, even though neither pathway requires ERE recognition.

Results

Mutations of a highly conserved DBD lysine (ERα.K206A/G), lead to super-activation of AP-1 through activation function dependent pathways, up to 200 fold. This super-activity can be elicited either through ER AFs 1 or 2, or that of a heterologous activation function (VP16). The homologous substitution in ERβ, K170A, or in ERα DBD-LBD leads to estrogen-dependent AP-1 activation and loss of the usually potent anti-estrogen effects. Each of numerous K206 substitutions in ERα, except K206R, eliminates anti-estrogen activation and this loss correlates perfectly with a loss of ability to titrate a repressive function from the RU486 bound progesterone receptor.

Conclusion

We conclude that ER DBDs contain a complex regulatory function that influences ligand activation profiles at AP-1. This function, which requires the integrity of the conserved lysine, both allows for activation at AP-1 with anti-estrogens (with ERβ and ERα DBD-LBD), and prevents ERα from becoming superactive at AP-1 with estrogens. We discuss the possibility that a repressor interaction with the DBD both mediates the AF-independent pathway and dampens the AF dependent pathway. Mutations in the conserved lysine might, by this model, disrupt the binding or function of the repressor.

Is phosphorylation of the alpha1 subunit at Ser-16 involved in the control of Na,K-ATPase activity by phorbol ester-activated protein kinase C?

The alpha1 subunit of Na,K-ATPase is phosphorylated at Ser-16 by phorbol ester-sensitive protein kinase(s) C (PKC). The role of Ser-16 phosphorylation was analyzed in COS-7 cells stably expressing wild-type or mutant (T15A/S16A and S16D-E) ouabain-resistant Bufo alpha1 subunits. In cells incubated at 37 degrees C, phorbol 12, 13-dibutyrate (PDBu) inhibited the transport activity and decreased the cell surface expression of wild-type and mutant Na,K-pumps equally ( approximately 20-30%). This effect of PDBu was mimicked by arachidonic acid and was dependent on PKC, phospholipase A(2), and cytochrome P450-dependent monooxygenase. In contrast, incubation of cells at 18 degrees C suppressed the down-regulation of Na,K-pumps and revealed a phosphorylation-dependent stimulation of the transport activity of Na,K-ATPase. Na,K-ATPase from cells expressing alpha1-mutants mimicking Ser-16 phosphorylation (S16D or S16E) exhibited an increase in the apparent Na affinity. This finding was confirmed by the PDBu-induced increase in Na sensitivity of the activity of Na,K-ATPase measured in permeabilized nontransfected COS-7 cells. These results illustrate the complexity of the regulation of Na,K-ATPase alpha1 isozymes by phorbol ester-sensitive PKCs and reveal 1) a phosphorylation-independent decrease in cell surface expression and 2) a phosphorylation-dependent stimulation of the transport activity attributable to an increase in the apparent Na affinity.

Identification of plasma proteins adsorbed on hemodialysis tubing that promote Staphylococcus aureus adhesion

Risk factors for Staphylococcus aureus infections in patients undergoing hemodialysis include underlying disease, material-induced host defects, and the presence of vascular access catheters. To determine the specific contribution of various potentially adsorbed plasma components in promoting S aureus adhesion to shunt tubing during chronic hemodialysis, we quantified their respective amounts by Western immunoblotting and densitometry and estimated their individual adhesion-promoting activities with specific adhesion-modified bacterial mutants. Fibrinogen, which was the only component consistently present in tubing protein extracts from all patients, was adsorbed in significantly higher amounts on predialyzer than on postdialyzer tubing segments. In contrast, fibronectin and von Willebrand factor were irregularly present in patients' tubing, whereas vitronectin or thrombospondin remained undetectable in all samples. The contribution of fibrinogen in promoting S aureus attachment to hemodialysis tubing was demonstrated by (1) the significantly lower adhesion of a cIfA mutant of strain Newman compared with its parent; (2) the increased attachment of strain 8325-4 after complementation with the cloned cIfA gene on the multicopy plasmid pCF4; and (3) the general tendency for strains Newman and 8325-4(pCF4) to express higher attachment on predialyzer compared with postdialyzer tubing segments in relationship with the higher content of fibrinogen on the former material. However, the specific S aureus attachment-promoting activity of both prefilter and postfilter tubing-adsorbed fibrinogen were much lower than that of the native in vitro-adsorbed protein and may reflect masking or inactivation of the in vivo-adsorbed protein by unknown mechanisms.

Cell shrinkage triggers the activation of mitogen-activated protein kinases by hypertonicity in the rat kidney medullary thick ascending limb of the Henle's loop. Requirement of p38 kinase for the regulatory volume increase response

The kidney medulla is exposed to very high interstitial osmolarity leading to the activation of mitogen-activated protein kinases (MAPK). However, the respective roles of increased intracellular osmolality and of cell shrinkage in MAPK activation are not known. Similarly, the participation of MAPK in the regulatory volume increase (RVI) following cell shrinkage remains to be investigated. In the rat medullary thick ascending limb of Henle (MTAL), extracellular hypertonicity produced by addition of NaCl or sucrose increased the phosphorylation level of extracellular signal-regulated kinase (ERK) and p38 kinase and to a lesser extent c-Jun NH(2)-terminal kinase with sucrose only. Both hypertonic solutions decreased the MTAL cellular volume in a dose- and time-dependent manner. In contrast, hypertonic urea had no effect. The extent of MAPK activation was correlated with the extent of MTAL cellular volume decrease. Increasing intracellular osmolality without modifying cellular volume did not activate MAPK, whereas cell shrinkage without variation in osmolality activated both ERK and p38. In the presence of 600 mosmol/liter NaCl, the maximal cell shrinkage was observed after 10 min at 37 degrees C and the MTAL cellular volume was reduced to 70% of its initial value. Then, RVI occurred and the cellular volume progressively recovered to reach about 90% of its initial value after 30 min. SB203580, a specific inhibitor of p38, almost completely inhibited the cellular volume recovery, whereas inhibition of ERK did not alter RVI. In conclusion, in rat MTAL: 1) cell shrinkage, but not intracellular hyperosmolality, triggers the activation of both ERK and p38 kinase in response to extracellular hypertonicity; and 2) RVI is dependent on p38 kinase activation.

From the molecular biology of prolactin and its receptor to the lessons learned from knockout mice models

Prolactin (PRL), a polypeptide hormone secreted mainly by the pituitary and, to a lesser extent, by peripheral tissues, affects more physiological processes than all other pituitary hormones combined since it is involved in > 300 separate functions in vertebrates. Its main actions are related to lactation and reproduction. The initial step of PRL action is the binding to a specific membrane receptor, the PRLR, which belongs to the class 1 cytokine receptor superfamily. PRL-binding sites have been identified in a number of tissues and cell types in adult animals. Signal transduction by this receptor is mediated, at least in part, by two families of signaling molecules: Janus tyrosine kinases and signal transducers and activators of transcription (STATs). Disruption of the PRLR gene has provided a new mouse model with which to identify actions directly associated with PRL or any other PRLR ligands, such as placental lactogens. To date, several different phenotypes have been analyzed and are briefly described in this review. Coupled with the SAGE technique, this PRLR knockout model is being used to qualitatively and quantitatively evaluate the expression pattern of hepatic genes in two physiological situations: transcriptomes corresponding to livers from both wild type and PRLR KO mice are being compared, and following statistical analyses, candidate genes presenting a differential profile will be further characterized. Such a new approach will undoubtedly open future avenues of research for PRL targets. To date, no pathology linked to any mutation in the genes encoding PRL or its receptor have been identified. The development of genetic models provides new opportunities to understand how PRL can participate to the development of pathologies throughout life, as for example the initiation and progression of breast cancer.

Glomerulonephritis and sodium retention: enhancement of Na+/K+-ATPase activity in the collecting duct is shared by rats with puromycin induced nephrotic syndrome and mice with spontaneous lupus-like glomerulonephritis

BACKGROUND

In rats with puromycin aminoglucoside-induced (PAN) nephrotic syndrome, micropuncture studies have localized the site of sodium retention to the collecting duct. We have confirmed this finding by demonstrating a two-fold increase in Na+/K+-ATPase activity specifically limited to the cortical collecting duct in PAN rats. To further define whether this phenomenon was dependent on the chemical induction of the nephrotic syndrome or was a general phenomenon observed in glomerulonephritis, we measured Na+/K+-ATPase activity in nephron segments from mice with spontaneous lupus-like nephritis.

METHODS

Hydrolytic activity of Na+/K+-ATPase was measured in three isolated nephron segments: proximal convoluted tubule, thick ascending limb and cortical collecting duct. The Na+/K+-ATPase activities were measured in PAN rats, sham-injected controls, and in (MRL x BXSB) F1 male mice which develop a well established spontaneous lupus-like glomerulonephritis by 4 months of age and their controls. Control mice have the same genetic background, but lack the Yaa mutant gene responsible for autoimmune acceleration and are free of glomerular lesions at 4 months of age.

RESULTS

In (MRL x BXSB) F1 male mice, Na+/K+-ATPase was similar to control mice in the proximal convoluted tubule and the thick ascending limb. In contrast, cortical collecting duct Na+/K+-ATPase activity was two times higher in (MRL x BXSB) F1 mice than controls. These results were identical to those observed in PAN rats compared to their sham-injected controls studied 7 days after an intraperitoneal injection of puromycin or isotonic saline, respectively.

CONCLUSIONS

Enhancement of Na+/K+-ATPase activity localized to the cortical collecting duct is a general characteristic of glomerulonephritis independent of its mode of induction, i.e. chemical versus autoimmune. Therefore, the experimental model of PAN is suitable to study the underlying mechanisms leading to Na+/K+-ATPase dysfunction.

Insulin-induced stimulation of Na+,K(+)-ATPase activity in kidney proximal tubule cells depends on phosphorylation of the alpha-subunit at Tyr-10

Phosphorylation of the alpha-subunit of Na+,K(+)-ATPase plays an important role in the regulation of this pump. Recent studies suggest that insulin, known to increase solute and fluid reabsorption in mammalian proximal convoluted tubule (PCT), is stimulating Na+,K(+)-ATPase activity through the tyrosine phosphorylation process. This study was therefore undertaken to evaluate the role of tyrosine phosphorylation of the Na+,K(+)-ATPase alpha-subunit in the action of insulin. In rat PCT, insulin and orthovanadate (a tyrosine phosphatase inhibitor) increased tyrosine phosphorylation level of the alpha-subunit more than twofold. Their effects were not additive, suggesting a common mechanism of action. Insulin-induced tyrosine phosphorylation was prevented by genistein, a tyrosine kinase inhibitor. The site of tyrosine phosphorylation was identified on Tyr-10 by controlled trypsinolysis in rat PCTs and by site-directed mutagenesis in opossum kidney cells transfected with rat alpha-subunit. The functional relevance of Tyr-10 phosphorylation was assessed by 1) the abolition of insulin-induced stimulation of the ouabain-sensitive (86)Rb uptake in opossum kidney cells expressing mutant rat alpha1-subunits wherein tyrosine was replaced by alanine or glutamine; and 2) the similarity of the time course and dose dependency of the insulin-induced increase in ouabain-sensitive (86)Rb uptake and tyrosine phosphorylation. These findings indicate that phosphorylation of the Na+,K(+)-ATPase alpha-subunit at Tyr-10 likely participates in the physiological control of sodium reabsorption in PCT.

Inhibition and restoration of prolactin signal transduction by suppressors of cytokine signaling

Prolactin (PRL) has been shown to activate the cytoplasmic tyrosine kinase Janus kinase 2 (Jak2) and the subsequent recruitment of various signaling molecules including members of the signal transducer and activator of transcription family of transcription factors. Recently, an expanding family of cytokine-inducible inhibitors of signaling has been identified that initially included four members: suppressor of cytokine signaling (SOCS)-1, SOCS-2, SOCS-3, and cytokine-inducible src homology domain 2 (SH-2) proteins. The present study analyzes the role of these members in PRL signaling. Constitutive expression of SOCS-1 and SOCS-3 suppressed PRL-induced signal transducer and activator of transcription 5-dependent gene transcription, and Jak2 tyrosine kinase activity was greatly reduced in the presence of SOCS-1 or SOCS-3. SOCS-1 was shown to associate with Jak2, whereas SOCS-2 was associated with the prolactin receptor. Co-transfection studies were conducted to further analyze the interactions of SOCS proteins. SOCS-2 was shown to suppress the inhibitory effect of SOCS-1 by restoring Jak2 kinase activity but did not affect the inhibitory effect of SOCS-3 on PRL signaling. Northern blot analysis revealed that SOCS-3 and SOCS-1 genes were transiently expressed in response to PRL, both in vivo and in vitro, whereas the expression of SOCS-2 and CIS genes was still elevated 24 h after hormonal stimulation. We thus propose that the early expressed SOCS genes (SOCS-1 and SOCS-3) switch off PRL signaling and that the later expressed SOCS-2 gene can restore the sensitivity of cells to PRL, partly by suppressing the SOCS-1 inhibitory effect.

Improvement of drug-induced chronic renal failure in lung transplantation

BACKGROUND

Nephrotoxicity is a frequently encountered adverse effect of calcineurin inhibitors (cyclosporine and tacrolimus)-combined immunosuppressive regimens.

METHODS

We have compared the glomerular filtration rate in 14 patients who underwent lung transplantation, before and after replacement of azathioprine by mycophenolate mofetil and reduction of associated calcineurin inhibitors doses.

RESULTS

After a mean follow-up of 16+/-4 months with the modified immunosuppressive regimen, the mean glomerular filtration rate increased by 20% with no change in lung function.

CONCLUSION

By its strong immunosuppressive effect, mycophenolate mofetil allows the decrease of associated calcineurin inhibitor doses, with subsequent improvement of renal function without jeopardizing the transplanted lung.

Dual effects of suppressor of cytokine signaling (SOCS-2) on growth hormone signal transduction

A family of suppressors of cytokine signaling (SOCS) has recently been identified of which two members have been shown to block growth hormone (GH) signaling. Dose-response experiments were conducted in 293 cells and SOCS-1 and SOCS-3 were shown to inhibit the transcriptional activation of a GH-responsive element and suppressed Jak2 tyrosine kinase activity. SOCS-2 had two opposite effects: at low concentrations it inhibited GH-induced STAT5-dependent gene transcription, but restoration of GH signaling was observed at higher concentrations. In cotransfection studies, SOCS-2 was able to block the inhibitory effect of SOCS-1 but not that of SOCS-3 on GH signaling. These findings suggest that a major function for SOCS-2 is to restore the sensitivity to GH by overcoming the initial inhibitory effects of other endogenous SOCS molecules.

Effect of cAMP on the activity and the phosphorylation of Na+,K(+)-ATPase in rat thick ascending limb of Henle

BACKGROUND

In rat kidney medullary thick ascending limb of Henle's loop (MTAL), activation of protein kinase A (PKA) was previously reported to inhibit Na+,K(+)-ATPase activity. This is paradoxical with the known stimulatory effect of cAMP on sodium reabsorption. Because this inhibition was mediated by phospholipase A2 (PLA2) activation, a pathway stimulated by hypoxia, we evaluated the influence of oxygen supply on cAMP action on Na+,K(+)-ATPase in MTAL.

METHODS

Ouabain-sensitive 86Rb uptake and Na+,K(+)-ATPase activity were measured in isolated MTALs. Cellular ATP content and the phosphorylation level of Na+,K(+)-ATPase were determined in suspensions of outer medullary tubules. Experiments were carried out under nonoxygenated or oxygenated conditions in the absence or presence of PKA activators.

RESULTS

cAMP analogues or forskolin associated with 3-isobutyl-1-methylxanthine (IBMX) inhibited ouabain-sensitive 86Rb uptake in nonoxygenated MTALs. In contrast, when oxygen supply was increased, cAMP stimulated ouabain-sensitive 86Rb uptake and Na+,K(+)-ATPase activity. Improved oxygen supply was associated with increased intracellular ATP content. The phosphorylation level of the Na+,K(+)-ATPase alpha subunit was increased by cAMP analogues or forskolin associated with IBMX in oxygenated as well as in nonoxygenated tubules. Under nonoxygenated conditions, the inhibition of Na+,K(+)-ATPase was dissociated from its cAMP-dependent phosphorylation, whereas under oxygenated conditions, the stimulatory effect of cAMP analogues on ouabain-sensitive 86Rb uptake was linearly related and cosaturated with the level of phosphorylation of the Na+,K(+)-ATPase alpha subunit.

CONCLUSION

In oxygenated MTALs, PKA-mediated stimulation of Na+,K(+)-ATPase likely participates in the cAMP-dependent stimulation of sodium reabsorption. Under nonoxygenated conditions, this stimulatory pathway is likely overridden by the PLA2-mediated inhibitory pathway, a possible adaptation to protect the cells against hypoxic damage.

Protein kinase A induces recruitment of active Na+,K+-ATPase units to the plasma membrane of rat proximal convoluted tubule cells

1. The aim of this study was to investigate the mechanism of control of Na+,K+-ATPase activity by the cAMP-protein kinase A (PKA) pathway in rat proximal convoluted tubules. For this purpose, we studied the in vitro action of exogenous cAMP (10-3 M dibutyryl-cAMP (db-cAMP) or 8-bromo-cAMP) and endogenous cAMP (direct activation of adenylyl cyclases by 10-5 M forskolin) on Na+,K+-ATPase activity and membrane trafficking. 2. PKA activation stimulated both the cation transport and hydrolytic activity of Na+,K+-ATPase by about 40%. Transport activity stimulation was specific to the PKA signalling pathway since (1) db-cAMP stimulated the ouabain-sensitive 86Rb+ uptake in a time- and dose-dependent fashion; (2) this effect was abolished by addition of H-89 or Rp-cAMPS, two structurally different PKA inhibitors; and (3) this stimulation was not affected by inhibition of protein kinase C (PKC) by GF109203X. The stimulatory effect of db-cAMP on the hydrolytic activity of Na+,K+-ATPase was accounted for by an increased maximal ATPase rate (Vmax) without alteration of the efficiency of the pump, suggesting that cAMP-PKA pathway was implicated in membrane redistribution control. 3. To test this hypothesis, we used two different approaches: (1) cell surface protein biotinylation and (2) subcellular fractionation. Both approaches confirmed that the cAMP-PKA pathway was implicated in membrane trafficking regulation. The stimulation of Na+,K+-ATPase activity by db-cAMP was associated with an increase (+40%) in Na+, K+-ATPase units expressed at the cell surface which was assessed by Western blotting after streptavidin precipitation of biotinylated cell surface proteins. Subcellular fractionation confirmed the increased expression in pump units at the cell surface which was accompanied by a decrease (-30%) in pump units located in the subcellular fraction corresponding to early endosomes. 4. In conclusion, PKA stimulates Na+,K+-ATPase activity, at least in part, by increasing the number of Na+-K+ pumps in the plasma membrane in proximal convoluted tubule cells.

Haemodynamic and endocrinological effects of noninvasive mechanical ventilation in respiratory failure

The aim of this study was to investigate the haemodynamic and endocrinological effects of noninvasive positive pressure ventilation (NIPPV). Eleven patients with oedema and recent hypercapnic and hypoxaemic worsening of a chronic respiratory insufficiency were included. Echocardiography, cardiac radionuclide assessment, blood catecholamines, salt and water handling hormones were measured at admission and discharge (long study (LS)). To discriminate between the action of NIPPV and other treatments, measurements were performed on the fourth day, for 4 h without NIPPV and 4 h with NIPPV (short study (SS)). NIPPV entailed a correction of P(a,CO2) and an increase of P(a,O2) in LS and SS. Oedema disappeared. Body weight decreased (from 85+/-42 to 81+/-40 kg) during LS. Systolic and mean pulmonary arterial pressure decreased in LS and SS. Right ventricular ejection fraction increased in LS. Left ventricular ejection fraction did not change. Cardiac index was normal on admission and then decreased. Natriuretic peptides and catecholamines were increased on admission, whereas plasma renin activity, aldosterone and vasopressin were normal. We suggest that in these patients, oedema can occur independently of renin-angiotensin-aldosterone-vasopressin and with a normal cardiac output. Noninvasive positive pressure ventilation allowed a correction of blood gases, associated with the resolution of oedema, a decrease in pulmonary arterial pressures and an increase in right ventricular ejection fraction.

[Choice of renal replacement therapy]

Renal replacement therapies (RRT) for acute renal failure patients consist of continuous or intermittent methods. Continuous renal replacement therapies (CRRT) are used in 54% of centers. Determinant for the choice of the continuous versus intermittent method is the clinical status of the patients. Those who are hemodynamically unstable, who receive a large fluid intake, who are anuric, who present with severe and persistent metabolic disorders such as acidosis or hyperkaliemia, and who are in respiratory failure, are preferably treated with CRRT. Once the patient has improved, he can be switched to intermittent RRT (IRRT). Thus CRRT and IRRT are complementary approaches. Dialysis material should be biocompatible; the RRT method used should guarantee stable hemodynamics. Coping with these two requirements reduces the time duration of renal recovery, diminishes the need for catecholamines and may improve the survival rate.

Mitochondrial anomalies in a Swiss family with autosomal dominant myoglobinuria

We report on a Swiss family in which 10 individuals of both sexes in 4 successive generations suffered from myoglobinuria, precipitated by febrile illness. It is the second family described with autosomal dominant inheritance of myoglobinuria. Four individuals suffered acute renal failure, which in two was reversible only after dialysis. In a recent case, a mitochondrial disorder was suspected because of an abnormal increase in lactate levels during an exercise test and because of a subsarcolemmal accumulation of mitochondria in a muscle biopsy, associated with a lack of cytochrome C oxidase in some muscle fibers. No mutation in the mitochondrial DNA was identified. Along with the inheritance pattern, these findings suggest that the myoglobinuria in this family is caused by a nuclear-encoded mutation affecting the respiratory chain.

Modulation of Na+,K(+)-ATPase activity by a tyrosine phosphorylation process in rat proximal convoluted tubule

1. In the rat kidney proximal convoluted tubule, epidermal growth factor and insulin have been reported to stimulate Na+ reabsorption. Because most of the effects of these growth factors are mediated by a process of tyrosine phosphorylation and Na+,K(+)-ATPase drives Na+ reabsorption, the influence of tyrosine kinases and tyrosine phosphatases on Na+,K(+)-ATPase activity located in the proximal convoluted tubule was evaluated. 2. Activation of receptor tyrosine kinases by epidermal growth factor and insulin stimulated ouabain-sensitive 86Rb+ uptake. The effects of epidermal growth factor and insulin were prevented by genistein, a tyrosine kinase inhibitor, but were unaffected by GF109203X, a protein kinase C inhibitor. 3. Inhibition of tyrosine phosphatases by orthovanadate (10(-7) and 10(-6)M) mimicked the effects of activation of receptor tyrosine kinases: stimulation of the ouabain-sensitive 86Rb+ uptake and of the hydrolytic activity of Na+,K(+)-ATPase under rate-limiting Na+ concentration, and absence of modification of the maximal activity (Vmax) of the enzyme. The effects of orthovanadate and insulin on the ouabain-sensitive 86Rb+ uptake were not additive. 4. The present results show that both activation of receptor tyrosine kinases and inhibition of tyrosine phosphatases stimulate the Na+,K(+)-ATPase activity through a common mechanism. Thus, a tyrosine phosphorylation process directly controls the Na+,K(+)-ATPase activity and contributes to the physiological control of water and solute reabsorption in the proximal convoluted tubule.

Stimulation of ouabain-sensitive 86Rb+ uptake and Na+,K+-ATPase alpha-subunit phosphorylation by a cAMP-dependent signalling pathway in intact cells from rat kidney cortex

We investigated in intact cortical kidney tubules the role of PKA-mediated phosphorylation in the short-term control of Na+,K+-ATPase activity. The phosphorylation level of Na+,K+-ATPase was evaluated after immunoprecipitation of the enzyme from 32P-labelled cortical tubules and the cation transport activity of Na+,K+-ATPase was measured by ouabain-sensitive 86Rb+ uptake. Incubation of cells with cAMP analogues (8-bromo-cAMP, dibutyryl-cAMP) or with forskolin plus 3-isobutyl-1-methylxanthine increased the phosphorylation level of the Na+,K+-ATPase alpha-subunit and stimulated ouabain-sensitive 86Rb+ uptake. Inhibition of PKA by H-89 blocked the effects of dibutyryl-cAMP on both phosphorylation and 86Rb+ uptake processes. The results suggest that phosphorylation by PKA stimulates the Na+,K+-ATPase activity.

Kinetics of cellular viability in warm versus cold ischemia conditions of kidney preservation. A biometric study

We have determined the kinetics of the cellular viability ratio (CVR), defined as the number of living cells over the total cell count, in pig kidneys using propidium iodide and fluorescein diacetate staining, as a function of time and preservation conditions. The kidneys were preserved in warm or cold ischemia in order to mimic the conditions of transplantation from non-heart-beating donors or multiple removal with optimal preservation of the graft, respectively. To determine the CVR, the cells were obtained by a fine-needle aspiration biopsy, which minimizes the damage to the graft. A biometric analysis by regression enabled the determination of the time dependence for warm ischemia (CVR(t) = 80.0 x e(-0.733-t)(+2.7/-0.36)) and for cold ischemia (CVR(t) = 80.0 x e(-0.022-t)(+1.57/-0.64)) with a confidence interval of 95%. These master curves allow us to predict, under the described conditions, the CVR after a given ischemia time. The half-life of the cells can be deduced from the time-dependent CVR(t), and is 0.64 hr (38 min) for warm ischemia and 21.4 hr for cold ischemia. Further, the CVR for a given kidney can be used to assess its condition at removal: if the CVR is below 48% at 2 hr after removal, one can conclude that the organ has suffered a period of warm ischemia.

Protein kinase C-dependent phosphorylation of Na(+)-K(+)-ATPase alpha-subunit in rat kidney cortical tubules

We have previously shown that, in oxygenated rat kidney proximal convoluted tubules (PCT), activation of protein kinase C (PKC) by phorbol 12,13-dibutyrate (PDBu) directly stimulates Na(+)-K(+)-adenosinetriphosphatase (ATPase) activity. PKC modulation of Na(+)-K(+)-ATPase activity by phosphorylation of its alpha-subunit was the postulated mechanism. The present study was therefore designed to investigate the relationship between PKC-mediated phosphorylation of the catalytic alpha-subunit and the cation transport activity of the Na(+)-K(+)-ATPase. In a suspension of rat kidney cortical tubules, activation of PKC by 10(-7) M PDBu increased the level of phosphorylation of the Na(+)-K(+)-ATPase alpha-subunit and stimulated the ouabain-sensitive 86Rb uptake by 47 and 42%, respectively. Time and dose dependence of the PDBu-induced increase in Na(+)-K(+)-ATPase activity and phosphorylation was strongly linearly correlated. The effects of PDBu on phosphorylation and activity of Na(+)-K(+)-ATPase were prevented by GF-109203X, a specific PKC inhibitor, whereas H-89, a specific PKA inhibitor, was ineffective. These results demonstrate that PKC activation induces phosphorylation of the catalytic alpha-subunit of Na(+)-K(+)-ATPase, which may participate in the stimulation of its cation transport activity in the rat PCT.

Preoperative inhibition of angiotensin-converting enzyme improves systemic and renal haemodynamic changes during aortic abdominal surgery

We studied 22 patients undergoing aortic surgery, allocated randomly to receive, before induction of anaesthesia, a single i.v. dose of enalapril 50 micrograms kg-1 or saline. During infrarenal aortic cross-clamping, we observed similar reductions in oxygen uptake in the two groups, despite greater systemic oxygen delivery in enalapril-treated patients; angiotensin-converting enzyme inhibition prevented the reduction in cardiac output and attenuated the decrease in glomerular filtration. Changes in glomerular filtration secondary to aortic clamping were related positively to changes in renal plasma flow (r = 0.83 (saline group) and r = 0.65 (enalapril group)). Creatinine clearance on the first day after operation was significantly higher in the enalapril compared with the saline group. We conclude that enalapril pretreatment is effective in improving systemic oxygen delivery, renal plasma flow and glomerular filtration during aortic abdominal surgery.

Complement depletion during haemofiltration with polyacrilonitrile membranes

BACKGROUND

Polyacrylonitrile (PAN, AN69) dialysis membranes have been shown to improve the outcome of critically ill patients. Factor D is an essential enzyme of the alternative pathway of complement and is increased during renal failure. On the other hand the contact of blood with biomaterials activates the complement cascade through the alternative pathway. PAN filters adsorb factor D which looses its enzymatic activity whilst bound to the membrane [1]; the complement alternative pathway function of serum exposed to PAN filters is greatly diminished and restored after addition of purified factor D [1]. The aim of our study was to measure the time course of factor D adsorption and its blood concentration during CVVH in critically ill patients with acute renal failure.

METHODS

We studied seven critically ill patients with ARF before, during and after continuous veno-venous haemofiltration (CVVH) with AN69.

RESULTS

There was a rapid decrease of factor D levels to 62(+/-6%) of the pre-CVVH value during the first 2 h, which continued to 51(+/-7.3%) after 12 h; at 24 h there was a slight rise to 62 +/- 12%. Sequential use of Polyacrylonitrile (AN69) filters lowered factor D levels below the normal plasma concentration in three patients, thus producing a state of factor D depletion.

CONCLUSION

The significant reduction of factor D levels during CVVH with PAN filters suggests that frequent changes of PAN filters may reduce alternative pathway function by lowering factor D levels. CVVH (as opposed to intermittent dialysis) with PAN membranes may further improve the outcome of critically ill patients.

Effect of insulin on Na+,K(+)-ATPase in rat collecting duct

1. The collecting duct is involved in the whole antinatriuretic effect of insulin, as indicated in vitro by the stimulatory effect of the hormone on ouabain-sensitive 86Rb+ uptake. Since Na+,K(+)-ATPase drives Na+ reabsorption, the contribution of the Na+ pump to the effect of insulin was investigated in rat isolated cortical and outer medullary collecting duct. 2. Insulin enhanced ouabain-sensitive 86Rb+ uptake in the absence, as well as in the presence, of either 5 x 10(-4) M amiloride or 10(-3) M hydrochlorothiazide (HCT). Maximal ouabain-sensitive 86Rb+ uptake, measured in Na(+)-loaded tubules, was also enhanced by insulin. The insulin effect persisted both in the absence of external Na+, when the Na+,K(+)-ATPase operates in a Rb(+)-Rb+ exchange mode, and in tubules depolarized by a high external concentration (20 mM) of Rb+ or by addition of 3 mM Ba2+. 3. Insulin treatment did not alter the intracellular Na and K concentrations, the specific binding of [3H]ouabain measured in intact tubules, or the hydrolytic activity of Na+,K(+)-ATPase measured after permeabilization of the tubule cells. 4. In conclusion, in the rat collecting duct, insulin increased Na+,K(+)-ATPase-mediated cation transport independently of Na+ availability, membrane potential and recruitment of pump units. The effect of insulin was lost after cell permeabilization, suggesting the presence of a cytosolic factor which controls the turnover of Na+,K(+)-ATPase.

[Acute kidney failure in tubular necrosis]

Tubular necrosis is the most frequent hospital-acquired cause of acute renal failure from renal origin. The two main factors leading to tubular necrosis are hemodynamic perturbations and use of nephrotoxic agents. There is recently a growing number of reports on tubular necrosis associated with a non traumatic rhabdomyolysis. In 60-70% of the cases, more than one contributing factor can be identified. In the majority of the patients who developed a transient postoperative acute renal failure, co-morbid factors such as diabetes, hypertension or major cardiovascular problems, are present. Acute renal failure increases the mortality by factors from 2-7. Therefore prevention and (or) early correction of the factors leading to tubular necrosis are of great importance.

Presence of two isoforms of Na, K-ATPase with different pharmacological and immunological properties in the rat kidney

Previous studies have demonstrated the presence of two populations of Na,K-ATPase with distinct kinetic, pharmacological and immunological characteristics along the rabbit nephron, indicating that the proximal segments of the nephron express exclusively the alpha 1 isoform of the catalytic subunit, whereas the collecting duct expresses an alpha 3-like isoform. Because pharmacological studies have shown the existence of two populations of Na,K-ATPase with different sensitivities to ouabain in the rat cortical collecting duct, which may result from the presence in the same nephron segment of the two isoforms demonstrated in the different segments of the rabbit nephron, the present study was undertaken to characterize the properties of Na,K-ATPase along the rat nephron. Results indicate that each segment of the rat nephron contains two subpopulations of Na,K-ATPase: a component highly sensitive to ouabain (IC50 approximately 5.10(-6) M) which is recognized by an anti-alpha 3 antibody and another moiety of lower affinity for ouabain (IC50 approximately 5.10(-4) M) which is recognized by an anti-alpha 1 antibody. Whether these two subpopulations correspond to different isoforms of the alpha subunit of Na,K-ATPase (alpha 1 and alpha 3-like) remains to be determined.

Protein kinase C-dependent stimulation of Na(+)-K(+)-ATP epsilon in rat proximal convoluted tubules

In rat proximal convoluted tubule (PCT), activation of protein kinase C (PKC) by phorbol 12,13-dibutyrate (PDBu) was previously reported to inhibit Na(+)-K(+)-ATPase, a paradoxical finding in view of the known stimulatory effect of PKC on Na+ reabsorption. Because this inhibition occurs via phospholipase A2 activation, a pathway stimulated by hypoxia, we evaluated the influence of oxygen supply on PKC action on Na(+)-K(+)-ATPase. Results confirmed that PDBu inhibited PCT Na(+)-K(+)-ATPase activity under usual conditions. In contrast, when oxygen supply was increased, PDBu had no effect on Na(+)-K(+)-ATPase hydrolytic activity, but it dose-dependently stimulated ouabain-sensitive 86Rb+ uptake. This latter effect, which was abolished by PKC inhibitors, resulted from an increment of the Na+ sensitivity of Na(+)-K(+)-ATPase. Thus, in oxygenated rat PCTs, activation of PKC primarily stimulated Na(+)-K(+)-ATPase. This likely contributes to increase solute reabsorption. Inhibition of Na(+)-K(+)-ATPase was observed only under hypoxic conditions. It may represent an adaptation to protect PCTs against deleterious effects of hypoxia.

Insulin unresponsiveness of tubular monovalent cation transport during fructose-induced hypertension in rats

1. Hyperinsulinaemia is considered to be a pathogenic factor for human and experimental hypertension. Thus, the contribution of the known insulin-stimulated tubular sodium reabsorption to this aetiological process has to be discussed. 2. Rats fed a fructose-enriched diet develop hyperinsulinaemia and hypertension, providing a model for studying the regulation of the tubular sodium handling and its possible relationship to hypertension. For this purpose, the sodium transport capacity of isolated nephron segments from control rats and from rats fed a fructose-enriched diet was investigated by measurement of ouabain-sensitive 86Rb uptake and of the hydrolytic activity of Na,K-ATPase. The number and affinity of insulin receptors were estimated from the specific [125I]insulin binding. 3. In rats fed a fructose-enriched diet, mild hypertension developed during the 14-day fructose diet. There were no differences, along the nephron, in basal 86Rb uptakes and ATPase activities between control rats and fructose-induced hypertensive rats. In control rats, insulin stimulated 86Rb uptake in the proximal convoluted tubule and cortical collecting duct, but exhibited an inhibitory action in the medullary thick ascending limb. In contrast, in fructose-induced hypertensive rats, 86Rb influx remained unresponsive to insulin concentrations ranging from 10(-11) to 10(-7) mol/l in the proximal convoluted tubule and cortical collecting duct. In the medullary thick ascending limb, the threshold of inhibition was displaced from 10(-11) mol/l up to 10(-7) mol/l. Insulin binding to the proximal convoluted tubule, medullary thick ascending limb and collecting duct were similar in control rats and in rats fed a fructose-enriched diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Anticoagulation in patients treated by continuous venovenous hemofiltration: a retrospective study

The most adequate anticoagulation regimen during extracorporeal renal replacement therapy can be difficult to define. Two hundred fifty-five critically ill patients with a mean age (+/- SD) of 58.2 +/- 16.3 years were treated by continuous venovenous hemofiltration (CVVH) between 1986 and 1992 in our intensive care units. Blood was circulated through hemofilters, either polyacrylonitrile (AN 69; Hospal, Lyon, France) or polyamide (FH 66; Gambro, Lund, Sweden), using a roller pump and an air safety system. The patients were classified into three subgroups according to the amount of heparin needed to achieve an adequate anticoagulation (ie, prevention of extracorporeal circuit clotting without inducing a patient's bleeding tendency): group 1, 37 patients who received no heparin (14.5%); group 2, 189 patients who received 100 to 700 IU/hr of heparin (74.1%); and group 3: 29 patients who received more than 700 IU/hr of heparin (11.4%). We analyzed the filter survival, the routine coagulation parameters, and the evolution of the patients for each group. Median duration of treatment was 144 hours (range, 4 to 1,152 hours). There were no differences in requirement of heparin among the two types of membrane: AN 69 (mean +/- SD), 393 +/- 106 IU/hr v FH 66, 374 +/- 35.3 IU/hr (range, 0 to 2,000 IU/hr). There were no relationships between the amount of heparin the patients received and the mean survival of the filters (group 1, 22.1 +/- 14.8 hr; group 2, 24.7 +/- 13.2 hr; group 3, 23 +/- 9.6 hr).(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin enhances sodium sensitivity of Na-K-ATPase in isolated rat proximal convoluted tubule

Insulin has been shown to stimulate the rate of ouabain-sensitive 86Rb influx in the isolated rat proximal convoluted tubule (PCT). To study the mechanism of this activation of Na-K-adenosinetriphosphatase (Na-K-ATPase), we determined the actions of insulin on 1) the maximal activity (Vmax) of Na-K-ATPase hydrolytic activity; 2) the maximal rate of ouabain-sensitive 86Rb influx (after intracellular Na loading); 3) the rate of ouabain-sensitive 86Rb influx under conditions where intracellular Na concentration is rate limiting, either in the presence or in the absence of 5 x 10(-4) M amiloride and/or low extracellular Na concentration (3 mM); and 4) the Na sensitivity of the Na-K-ATPase hydrolytic activity. The maximal rates of Na-K-ATPase hydrolytic activity and of ouabain-sensitive 86Rb uptake were unchanged by insulin. In contrast, we confirmed that insulin enhanced 86Rb uptake (in peq.mm-1.min-1) in the absence of inhibitor of the Na/H exchanger [18.2 +/- 1.7 to 24.1 +/- 1.3 (SE), P < 0.03] and, in addition, demonstrated a similar stimulation in the presence of either 5 x 10(-4) M amiloride (7.2 +/- 0.6 to 10.7 +/- 0.9, P < 0.01), 3 mM extracellular Na (4.1 +/- 0.4 to 5.6 +/- 0.2, P < 0.05), and both amiloride and 3 mM extracellular Na (2.1 +/- 0.7 to 4.5 +/- 0.4, P < 0.03). Finally, insulin increased the sensitivity of Na-K-ATPase to Na as the apparent dissociation constant decreased from 46.5 +/- 5.3 to 27.6 +/- 3.0 mM (P < 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Fenoldopam improves renal hemodynamics impaired by positive end-expiratory pressure

BACKGROUND

Mechanical ventilation with positive end-expiratory pressure (PEEP) can impair renal hemodynamics. Fenoldopam, a dopamine receptor agonist, has been shown, in animal experiments, to improve renal perfusion. The purpose of the current study was to examine the effects of this agent on altered renal hemodynamics secondary to positive pressure ventilation.

METHODS

Twelve patients requiring mechanical ventilation of their lungs and PEEP for the treatment of hypoxemia after multiple trauma or visceral surgery were studied. Hemodynamic variables, renal vascular resistance, urine flow, creatinine, inulin and PAH clearance, and excretion of sodium and potassium (NaE and KE) were measured before and after introduction of a level of PEEP high enough to decrease urine flow rate by 25% or more, and after administration of intravenous fenoldopam.

RESULTS

No hemodynamic effect resulted from 0.1 microgram.kg-1.min-1, but 0.2 micrograms.kg-1.min-1 fenoldopam decreased both diastolic and mean arterial blood pressure from 66 +/- 37 (mean +/- SEM) to 57 +/- 21 mmHg, and from 83 +/- 3 to 74 +/- 4 mmHg, respectively. Renal vascular resistance was reduced from 54 +/- 12 to 19 +/- 5 dynes.s.cm-5 at 0.2 micrograms.kg-1.min-1. Fenoldopam produced a dose-related increase in renal blood flow and PAH clearance. With 0.2 micrograms.kg-1.min-1 fenoldopam, urine flow increased from 81 +/- 25 to 116 +/- 29 ml/h, NaE from 28 +/- 7 to 85 +/- 70 microM/min, and KE from 65 +/- 12 to 109 +/- 16 microM/min.

CONCLUSIONS

The results of the current study indicate that intravenous fenoldopam at a dose of 0.2 micrograms.kg-1.min-1 improves renal hemodynamics and increases Na and K excretion in patients requiring mechanical ventilation of their lungs and PEEP. These effects are probably caused by an increased kidney perfusion secondary to renal artery vasodilation.

Mechanism of enhanced Na-K-ATPase activity in cortical collecting duct from rats with nephrotic syndrome

The maximal hydrolytic activity of Na-K-ATPase is specifically increased in the cortical collecting duct (CCD) of rats with puromycin-induced nephrotic syndrome (NS). This stimulation is independent of aldosterone and of endogenous ouabain-like substance. To investigate the mechanism responsible for this change, we compared the maximal Na-K-ATPase hydrolytic activity, the ouabain sensitive 86Rb influx, the specific [3H]ouabain binding, and the sensitivity of Na-K-ATPase to ouabain in the CCD of control rats and of rats given an intraperitoneal injection of puromycin 7 d before study. Both Na-K-ATPase activity and ouabain-sensitive 86Rb influx increased two-fold in rats with NS (ATPase activity: 34.1 +/- 2.1 vs. 18.0 +/- 0.7 pmol.mm-1 x min-1 +/- SE, n = 6, P < 0.001; Rb influx: 14.4 +/- 0.7 vs. 7.4 +/- 0.4 peq.min-1 +/- SE, n = 6, P < 0.001) whereas specific [3H]ouabain binding decreased in rats with NS (6.9 +/- 0.7 vs. 9.0 +/- 0.6 fmol.mm-1 +/- SE, n = 6, P < 0.005). Therefore, the maximal turnover rate of Na-K-ATPase increased over twofold in rats with NS (5,053 +/- 361 vs. 2,043 +/- 124 cycles.min-1 +/- SE, n = 6, P < 0.001). Analysis of the curves of inhibition of Na-K-ATPase by ouabain showed the presence of two Na-K-ATPase populations in both control and NS rats: a highly sensitive population (apparent Ki: 1.4 x 10(-6) M and 0.9 x 10(-6) M) and a less sensitive moiety (apparent Ki: 2.6 x 10(-4) M and 1.1 x 10(-4) M). The enhancement of Na-K-ATPase activity observed in the CCD of rats with NS was entirely due to the stimulation of the population of Na-K-ATPase with low ouabain sensitivity. These results suggest that a dysregulation of this subclass of Na-K-ATPase might be the primary cause of sodium retention in this model of nephrotic syndrome.

Natriuretic and vasoactive hormones and glomerular hyperfiltration in hyperglycaemic type 2 diabetic patients: effect of insulin treatment

Evidence that an increase in plasma atrial natriuretic peptide (ANP) concentrations mediates, at least in part, glomerular hyperfiltration in diabetic rats prompted us to study the relationship between ANP and renal haemodynamics in hyperfiltering type 2 diabetic patients in association with other hormones implicated in the control of glomerular filtration rate (GFR) (catecholamines, vasopressin, renin) and in sodium tubular transport (aldosterone, ouabain-displacing factor, ODF). Since hyperglycaemia is also associated to hyperfiltration, diabetic patients who presented with secondary drug failure were studied both in hyperglycaemic and in normoglycaemic condition. For this purpose, 11 normotensive non-macroproteinuric hyperfiltering patients with type 2 diabetes were treated with an 8-day continuous insulin infusion (days 0-7). Dehydration was prevented or corrected and natriuresis was on day 0 above 100 mmol/day. The following parameters were determined on days 0 and 7: GFR and renal plasma flow (RPF) by 99mTc-DTPA and 131I-hippuran clearances; the extracellular volume, assimilated to the DTPA diffusion volume; urinary ODF by receptor-binding assay and urinary as well as plasma catecholamines by HPLC after extraction on alumin. Plasma ANP and antidiuretic hormone (ADH) were measured by radioimmunoassay after extraction on phenyl-silylsilica (ANP) and with ether (ADH). Unextracted plasma was used for radioimmunological measurement of plasma renin activity and aldosterone. When correcting hyperglycaemia to normoglycaemia GFR decreased from high to normal mean value (138 +/- 27 and 115 +/- 6 ml/min, p < 0.001), RPF followed the same trend, and the DTPA diffusion volume did not change.(ABSTRACT TRUNCATED AT 250 WORDS)