Glomerulonephritis for the generalist.

Glomerulonephritis is a common renal disorder, and a leading cause of end-stage renal disease. Glomerulonephritis can present in protean ways, with general features including proteinuria, hematuria, renal failure, and hypertension. Recent advances in our knowledge of glomerulonephritis have indicated that in many cases early therapeutic intervention can lead to improvement in renal function, long-term preservation of renal function, or slowing of the progression to end-stage renal failure. The goal of this review is to describe the method of evaluation of glomerulonephritis, stress the importance of general measures to preserve renal function or slow the rate of progression of disease, and finally to familiarize the reader with distinct categories of disease and their treatment.

Regulation of cytoplasmic calcium levels by two nitric oxide receptors.

We examined the effects of dissolved nitric oxide (NO) gas on cytoplasmic calcium levels ([Ca(2+)](i)) in C6 glioma cells under anoxic conditions. The maximum elevation (27 +/- 3 nM) of [Ca(2+)](i) was reached at 10 microM NO. A second application of NO was ineffective if the first was >0.5 microM. The NO donor diethylamine/NO mimicked the effects of NO. Acute exposure of the cells to low calcium levels was without effect on the NO-evoked response. Thapsigargin (TG) increased [Ca(2+)](i) and was less effective if cells were pretreated with NO. Hemoglobin inhibited the effects of NO at a molar ratio of 10:1. 8-Bromo-cGMP was without effect on the NO-evoked response. If cells were pretreated with TG or exposed chronically to nominal amounts of calcium, NO decreased [Ca(2+)](i). The results suggest that C6 glioma cells have two receptors for NO. One receptor (NO(A)) elevates [Ca(2+)](i) and resides on the endoplasmic reticulum (ER). The other receptor (NO(B)) decreases [Ca(2+)](i) and resides on the plasmalemma or the ER. The latter receptor dominates when the level of calcium within intracellular stores is diminished.

Isovolumetric regulation of rat glial cells during development and correction of hypo-osmolality.

Rat C6 glioma cells undergo regulatory volume decrease (RVD) following sudden exposure to hypo-osmolality, but little or no regulatory volume increase (RVI) is observed when cells cultured in hypo-osmotic media are suddenly returned to isoosmolality. Because C6 glioma cells would rarely be exposed to sudden large changes in osmolality in vivo, we examined the ability of these cells to maintain their volume, termed 'isovolumetric regulation', when exposed to gradual changes in osmolality. When osmolality was gradually reduced by reduction of NaCl concentration from 300 to 250 mOsmol/kg at a rate of 0.4 mOsmol/kg/min or less cells were able to maintain their volume, while at higher rates, the cells swelled. Cells which were cultured in hypo-osmotic (200 mOsmol/kg) media for 3 days exhibited isovolumetric regulation at rates of osmolality increase of 0.5 mOsmol/kg/min or less over the range of 200-250 mOsmol/kg. We conclude that rat C6 glioma cells can sensitively regulate their volume over the osmolality range of pathophysiologic interest at rates of osmolality change which are faster than those generally seen in clinical conditions.

Increased levels of serum hepatocyte growth factor in patients with end-stage renal disease.

Blood levels of hepatocyte growth factor (HGF) have been found to be elevated in patients with chronic renal failure. The cause of the increase in this mitogen is unclear. We determined serum HGF levels in 34 patients on maintenance dialysis and ten healthy volunteers. Predialysis serum HGF levels were elevated in patients with end-stage renal disease as compared to control subjects (1.65 +/- 0.2 ng/mL vs 0.46 +/- 0.04 ng/mL, p<0.01). In addition, serum HGF levels were significantly higher in African-American dialysis patients compared to Caucasian patients (2.18 +/- 0.36ng/mL vs 1.18 +/- 0.12ng/mL, p<0.01). The observed differences could not be accounted for by variations in serum creatinine, serumalbumin, or blood pressure between the African-American and Caucasian patients. Serum HGF levels were elevated in patients with end-stage renal disease, and were higher in African-American than Caucasian patients, but the pathophysiology and significance of this finding remain unclear.

Enzymatic modulation of cell volume in C6 glioma cells.

We monitored the volume of C6 glioma cells in suspension using a Coulter Counter and exposed the cells to micromolar or nanomolar levels of collagenase or clostripain. In 13 experiments, type IV collagenase (310 units ml-1; approximately 3 microM L-1) decreased the volume by 8-12%, 8 min after addition. In 13 of 21 experiments, the volume decrease was followed by a volume regulatory increase (VRI) back to control levels in the continued presence of collagenase. The shrinkage evoked by type IV collagenase was eliminated by heat-inactivation of the enzyme preparation. A highly purified collagenase (type VII) at the same concentration evoked a relatively minor decrease in volume. A well-known contaminating protease present in type IV collagenase, clostripain, which specifically cleaves arginyl peptide bonds, evoked a 7 +/- 2% shrinkage (100 nM L-1, 7 experiments). Clostripain did not evoke a volume regulatory increase. The initial velocity of shrinkage evoked by clostripain (0.0012 pL min-1, 0.0034 pL min-1, 0.0132 pL min-1; 1 pL = 10(-12) liters) scaled with its concentration (1 nM L-1, 10 nM L-1, 100 nM L-1). The effect of clostripain was inhibited by heat-inactivation of the enzyme. Leupeptin, an inhibitor of clostripain, prevented the decrease in volume evoked by clostripain. The activity of stretch-activated ion channels was unaffected by type IV collagenase. Barium, cesium, amiloride, DIDS, or bumetanide failed to block the shrinkage evoked by type IV collagenase. These results demonstrate that clostripain, present in crude collagenase enzyme preparations, causes the shrinkage, and that C6 glioma cells can undergo a volume regulatory increase at virtually constant osmotic pressure. In addition, cleavage of a cell surface moiety, which contains arginine, and possibly proline, causes shrinkage. This moiety may be part of the extracellular or intracellular matrix providing mechanical support to the cells. VRI reflect actions of another substance in the type IV crude collagenase preparations, on a receptor independent of the arg-pro moiety. The enzymatic modulation of glioma cell volume by these two receptors may reflect a new mechanism by which such cells, and possibly other glia, regulate their contact area and interactions with other cells in the central nervous system.

Mycobacterium marinum infection in a renal transplant recipient.

BACKGROUND: Infections with atypical mycobacteria occur more frequently in patients with solid organ transplants than in the normal host. METHODS: We report a case of cutaneous Mycobacterium marinum infection in a renal transplant recipient. The patient presented with nodules on the forearm after returning from a fishing trip and was treated for cellulitis without success. RESULTS: Cultures of a biopsy of the lesion grew M. marinum. The patient was treated with ethambutol and ciprofloxacin with a good response; however, 9 months of treatment were required for complete resolution. CONCLUSION: Immunosuppressive therapy for renal transplantation increases susceptibility to a variety of opportunistic infections. A patient who presents with nodules on the extremities should be questioned regarding contact with fish, aquatic environments, or fish tank water, in which case infection with M. marinum should be considered. The diagnosis and treatment of this infection in transplant recipients is discussed.

Renal papillary necrosis in a patient with sickle cell trait.

A patient with sickle cell trait who presented with gross hematuria and was subsequently found to have renal papillary necrosis is presented. The hematuria resolved with conservative therapy consisting of bed rest and hydration with hypotonic intravenous fluids. The pathophysiology of renal abnormalities associated with sickle cell trait is described. The management of the primary clinical manifestations of this disorder, hematuria and papillary necrosis, are discussed.

Mechanotransducing ion channels in C6 glioma cells.

Mechanotransducing (MS) ion channels and images of the patch membrane were studied in cell-attached patches in C6 glioma cells. MS channel density was approximately 0.08 to 0.5 channels/microns2, channel conductance was approximately 40 pS (at -40 mV), and the reversal potential was +15 mV. Replacement of NaCl with KCl, CsCl, or Na gluconate in the pipette solution was without substantial effect on the current-voltage relationship. Replacement of NaCl with NMDG (N-Methyl-D-Glucamine) Cl or reducing NaCl decreased the amplitude of inward currents at negative membrane potentials and caused the reversal potential to shift in the negative direction. Rapid application of suction to the back of the pipette usually elicited a fast (< 0.1 s) appearance of channel activity. The peak (phasic) in channel activity was followed by a decrease to a constant (tonic) level of activity. The reduction in channel activity--called adaptation--was reduced at depolarizing membrane potentials and disappeared if too much pressure was applied. Positive pressure caused the patch membrane to curve toward the pipette tip, move in the direction of the tip, and evoke MS channel activity. Removal of the positive pressure caused the patch to move back to the original position. Conversely, negative pressure caused the patch membrane to curve away from the pipette tip, move away from the tip, and elicit MS channel activity. Gigohm seal resistances were always maintained during translational movement of the patch membrane. Tonic MS channel activity was not associated with translational movements of the patch membrane. Phasic and tonic channel activity were independent of the sign of curvature of the patch membrane. C6 glioma cells have rapidly adapting voltage-dependent MS ion channels, which are non-selective for monovalent cations, and belong to the stretch-activating class of mechanosensory ion channels. Adaptation in MS channels may allow the cell to limit the influx of cations in response to mechanical input. The selective loss of adaptation suggests that the MS channel's gate receives input from two sources. A minimal viscoelastic mechanical model of adaptation and two alternative models for translational movement of the patch are presented.

Mechanisms of hypoosmotic volume regulation in glioma cells.

Rat C6 glioma cells undergo regulatory volume decrease (RVD) following hypoosmotic exposure. RVD was inhibited by the K+ channel blockers barium (10 mM) and quinine (1 mM). The mechanism of activation of the volume regulatory process was studied. Volume regulation was not observed following incubation of cells in Ca(2+)-free medium. Fluorescent measurement of intracellular free Ca2+ revealed no change following hypoosmotic exposure. Okadaic acid, an inhibitor of protein phosphatase type 1 and 2A inhibited VRD in C6 glioma cells. These results suggest that hypoosmotic RVD in C6 glioma cells involves a loss of K+ (and anion) from the cell. The activation of K+ loss is dependent on the presence of extracellular calcium (but not an increase in intracellular free calcium); and on protein dephosphorylation, either of a transport protein or another protein in the signalling pathway.

Osmotic demyelination syndrome following correction of hyponatremia: association with hypokalemia.

The osmotic demyelination syndrome (ODS) is a neurologic complication associated with rapid correction of hyponatremia. A case is described in which the patient was found to have hypokalemia as well as hyponatremia prior to the development of ODS. The literature was reviewed for cases of ODS in which patients had hyponatremia (serum sodium < or = 126 mmol/L) at presentation followed by correction of the hyponatremia. Of the 74 cases in which serum sodium and serum potassium values were reported at the time of presentation, 66 patients (89%) had hypokalemia. In 20 of these cases, serial measurements of sodium and potassium were reported, and in no instance was the potassium level normalized prior to the time of most rapid correction of the serum sodium. Hypokalemia may predispose patients to develop osmotic demyelination following correction of hyponatremia. The etiology of this complication is unclear. In neurologically stable patients with severe hyponatremia, it may be beneficial to correct hypokalemia prior to correction of the serum sodium. This maneuver may further reduce the incidence of ODS.

Organic osmolytes in acute hyponatremia.

The defense of brain volume during hyponatremia cannot be explained by the losses of brain sodium and potassium. We have examined the brain losses of organic osmolytes in rats after 24 h of severe hyponatremia induced by the administration of vasopressin and 5% dextrose in water. Normonatremic controls and animals with intermediate plasma sodium concentration ([Na]) were produced in vasopressin-treated animals by the administration of isocaloric gavages containing varying amounts of NaCl and free water. The animals were killed at 24 h by decapitation, and one brain hemisphere was quickly frozen in liquid nitrogen for organic osmolyte determinations. When compared with controls (plasma [Na] = 139 +/- 1.5 mM), hyponatremic animals (plasma [Na] = 96 +/- 1 mM) had significantly reduced brain contents for sodium, potassium, chloride, glutamate, myo-inositol, N-acetylaspartate, aspartate, creatine, taurine, gamma-aminobutyric acid, and phosphoethanolamine. Plasma [Na] was highly correlated (P < 0.001) with the brain contents for sodium, potassium, and organic osmolytes. Whereas the observed increase in brain water during hyponatremia was only 4.8%, by calculation, brain swelling without brain organic osmolyte losses would have been 11%, an amount that jeopardizes survival.

Brain osmoregulation during extreme and moderate dehydration in a rat model of severe DKA.

To determine if osmoprotective molecules accumulate in the brain during severe DKA with extreme (DKA-E) and moderate (DKA-M) dehydration, Fischer 344 rats (250-350g) were given STZ 45 mg/kg (i.p.) and allowed food and water ad lib. DKA-M received NaCl 77 mmol/L 60 ml/kg (i.p.) q 4 hrs. on day 2. All rats were anesthetized and sacrificed at 48 hrs. Half of each brain was used to measure water content (BWC) and half to measure Na+, K+, and organic osmoles by HPLC. Just prior to expiration, values for mean concentration of serum glucose (mmol/L) percent weight loss and median blood pH for DKA-E were 33.4, 19%, 6.98; for DKA-M, 16.8, 7.5% and 6.84, respectively. Means +/- SEM were compared by Student's t-test. Percent BWC was 76.3, 77.3 and 77.6 in DKA-E, DKA-M and normal controls, respectively (NS). Brain Na+ and K+ were increased in DKA-M compared to controls (p < .05) but not significantly different in DKA-E compared to controls. Of organic osmoles measured (umol/g wet weight) taurine was significantly increased (p < .01) in DKA-E and DKA-M (8.04 +/- .39 and 9.73 +/- .78, respectively) as compared to controls (5.92 +/- .35) as was myoinositol in DKA-E compared to controls (9.96 +/- .39 vs. 8.87 +/- .28) (p < .05) and urea in DKA-E as compared to controls (14.24 +/- 3.9 vs. 4.14 +/- .52) (p < .01). DKA-M were not significantly different for brain myoinositol or urea as compared to control animals. There was no significant difference in brain glutamine between either study group and controls. Preservation of brain water despite systemic dehydration can be partly explained by increased brain concentrations of osmoprotective molecules. Such adaption in the clinical setting of DKA warrants a cautious repair of dehydration and hyperosmolality.

Minimizing hemorrhagic complications in dialysis patients.

Renal failure is associated with an increased incidence of hemorrhage from a variety of sites, particularly in patients undergoing surgical procedures. The primary factors in the pathogenesis of bleeding in renal failure are platelet biochemical abnormalities and alterations in platelet vessel wall interactions. Hemodialysis improves hemostatic abnormalities in uremia, but the need for heparinization during the procedure may increase the bleeding risk. The risk of bleeding may be minimized by using peritoneal dialysis or alternative means to routine heparinization to prevent clotting in the extracorporeal circulation during hemodialysis. These include use of minimal heparin, prostacyclin, regional citrate anticoagulation, and no anticoagulation. Continuous arteriovenous hemodialysis may also be performed with regional citrate anticoagulation. There are several nondialytic therapies that may be used to prevent or treat hemorrhage in renal failure patients. These include administration of cryoprecipitate, 1-deamino-8-arginine vasopressin, estrogens, red blood cells, and erythropoietin. A clinical strategy to minimize bleeding complications in dialysis patients is presented.

Osmoregulatory betaine uptake by rat renal medullary slices.

Betaine is an osmolyte present in high concentrations in renal medullary cells. Betaine and other organic osmolytes, such as glycerophosphorylcholine, myo-inositol, and sorbitol, have been shown to increase in concentration during antidiuresis when the inner medullary extracellular osmolality rises. Its concentration may increase in renal cells either by betaine uptake or by choline metabolism to betaine. These studies measured the uptake of (14C)betaine into cortical, outer medullary and inner medullary slices from rat kidney. The tissue-to-medium ratio of (14C) betaine increased with increasing osmolality up to 450 mosmol/kg in outer medullary and inner medullary slices, but not in cortical slices. Betaine uptake increased when the osmolality was raised with NaCl or mannitol, but not with urea. When LiCl was substituted for NaCl in a medium of 300 mosmol/kg, there was significant inhibition of betaine uptake, although the tissue-to-medium ratios remained greater then unity. Thus, increases in osmolality stimulate betaine uptake in rat renal medullary slices and this uptake occurs by both sodium-dependent and sodium-independent betaine transport.

Effect of vanadate on renal hypertrophy and sorbitol accumulation in streptozotocin induced diabetes in rats.

Vanadate has been previously shown to normalize blood glucose in streptozotocin-induced diabetic (STZ-DM) rats. The effect of a previously studied dose of vanadate (0.8 mg/ml) in drinking water on blood glucose, renal hypertrophy, and whole kidney polyol accumulation was studied in STZ-DM rats. Rats with diabetes of 5 weeks duration had higher blood glucose, greater urinary output, higher kidney weight, lower body weight, and higher kidney to body weight ratios than controls. Whole kidney sorbitol concentrations were significantly increased in diabetes but myo-inositol levels were unchanged vs control animals. After four weeks of oral vanadate treatment, blood glucose, urine volume, and kidney weights were similar to control values. Kidney to body weight ratios fell below that of the STZ-DM animals, but because body weights remained decreased, the kidney to body weight ratios were not normalized. Renal sorbitol levels returned to control values and renal myo-inositol levels remained unchanged in STZ-DM and normal animals treated with vanadate. These results provide evidence that vanadate therapy may result in regression of the hypertrophy and polyol accumulation characteristic of diabetic nephropathy in STZ-DM rats. This effect is most likely due to normalization of blood glucose by the insulin-mimetic activity of vanadate treatment.

Isovolumetric regulation of renal proximal tubules in hypotonic medium.

Isolated nonperfused proximal tubules maintained their cell volume at a constant level (isovolumetric regulation, IVR), when osmolality of the bathing medium was gradually decreased from 290 to 190 mosm at 1.5 and 5.0 mosm/min. Hypotonic IVR was blocked by inhibiting the Na(+)-K+ pump with ouabain (10(-4) M) when osmolality was decreased at 1.5 or 5 mosm/min. Concentration-dependent inhibition of cell volume maintenance was observed in the presence of the K+ channel blocker barium (10(-3)-10(-2) M) when osmolality decreased at 5 mosm/min. Quinine (10(-3) M), another K+ channel blocker, also inhibited IVR at osmolality decreases of 1.5 and 5 mosm/min. These results suggest that the maintenance of constant cell volume during gradual hypoosmotic exposure involves mechanisms that depend on intact Na-K-ATPase and the controlled loss of intracellular K+.

Volume regulation determinants in isolated proximal tubules in hypertonic medium.

Isolated nonperfused proximal tubules maintained their cell volume at a constant level [isovolumetric regulation (IVR)] when extracellular osmolality was gradually increased above 295 mosmol at 1.5 mosmol/min. Cell volume remained constant between 295 and 361 +/- 7 mosmol in medium containing HCO3- -CO2 as the major buffer. In N-2-hydroxyethyl piperazine-N'-2-ethanesulfonic acid-buffered medium, IVR maintained cell size constant between 295 and 370 +/- 11 mosmol; thus, the volume regulatory process did not require the presence of external HCO3- -CO2. Omission of medium phosphate and sulfate from defined bathing medium had no effect on the volume regulatory process, whereas acetate (5 mM) was required to maintain cell volume constant. Hypertonic IVR was inhibited by acetazolamide (10(-6) M), 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (2.5 x 10(-5) M), and, in medium in which choline replaced all but 25 mM of Na+, amiloride (1 mM). These results suggest the involvement of carbonic anhydrase, Cl-, and HCO3- transport, and Na-H exchange in IVR; and provide indirect support for the view that IVR in hyperosmotic medium depends on the intracellular accumulation of electrolytes resulting from altered rates of membrane ionic exchange mechanisms.

Safety of regional citrate hemodialysis in acute renal failure.

Regional citrate anticoagulation is an alternative to heparin anticoagulation for hemodialysis of patients at increased risk of bleeding. We report the successful use of this technique in 326 dialyses in 49 high bleeding risk patients with acute renal failure. Systemic anticoagulation did not occur as a result of any dialysis procedure, and in no instance was bleeding observed. Dialysis was effective, as judged by removal of creatinine. The safety of this procedure is demonstrated by the lack of bleeding complications and the small incidence of electrolyte and acid-base abnormalities. In addition we document the absence of citrate intoxication by serial measurements of serum citrate levels. Regional citrate anticoagulation is a safe and effective method of performing hemodialysis in patients with acute renal failure at increased risk of bleeding.