Netrin G1 Is a Novel Target Antigen in Primary Membranous Nephropathy

BACKGROUND

Primary membranous nephropathy (MN) is caused by circulating autoantibodies binding to antigens on the podocyte surface. PLA2R1 is the main target antigen in 70%-80% of cases, but the pathogenesis is unresolved in 10%-15% of patients.

METHODS

We used native western blotting to identify IgG4 autoantibodies, which bind an antigen endogenously expressed on podocyte membranes, in the serum of the index patient with MN. These IgG4 autoantibodies were used to immunoprecipitate the target antigen, and mass spectrometry was used to identify Netrin G1 (NTNG1). Using native western blot and ELISA, NTNG1 autoantibodies were analyzed in cohorts of 888 patients with MN or other glomerular diseases.

RESULTS

NTNG1 was identified as a novel target antigen in MN. It is a membrane protein expressed in healthy podocytes. Immunohistochemistry confirmed granular NTNG1 positivity in subepithelial glomerular immune deposits. In prospective and retrospective MN cohorts, we identified three patients with NTNG1-associated MN who showed IgG4-dominant circulating NTNG1 autoantibodies, enhanced NTNG1 expression in the kidney, and glomerular IgG4 deposits. No NTNG1 autoantibodies were identified in 561 PLA2R1 autoantibodies-positive patients, 27 THSD7A autoantibodies-positive patients, and 77 patients with other glomerular diseases. In two patients with available follow-up of 2 and 4 years, both NTNG1 autoantibodies and proteinuria persisted.

CONCLUSIONS

NTNG1 expands the repertoire of target antigens in patients with MN. The clinical role of NTNG1 autoantibodies remains to be defined.

Prolonged Magnesium Deficiency Causes Osteoporosis in the Rat

BACKGROUND

Peroral magnesium (Mg) administration, used as the only treatment in postmenopausal osteoporosis, has been shown to cause a significant increase of BD.

OBJECTIVES

To gauge the role of magnesium deficiency in the etiology of osteoporosis, we compared rats fed a Mg deficient diet daily with rats fed a Mg adequate diet over a period of one year.

METHODS

Sprague-Dawley female rats (mean weight 110, SD 23 g) were divided into two groups of 8 and randomly assigned to an identical semisynthetic diet, containing either 2000 ppm (group A) or 200 ppm Mg (group B). Urine samples were collected every 3 months and blood samples at end of trial. After sacrifice, L3-L5 vertebrae and the femoral regions were examined for bone density (BD) using dual energy X-ray absorptiometry. The femurs were examined for bone fragility, the tibias by histomorphometry and the mineral contents of the bones was estimated.

RESULTS

The mean BD of L3-L5 vertebral bone (BDL) was significantly higher in group than in the Mg deficient group B (p = 0.035, 1 tail). The BD of the femoral region (BDF) was also significantly higher in group A (p = 0.045, 1 tail). The stiffness of the femur, as determined by resistance to bending, was slightly greater in group A than in group B, but after correction to diminish the influence of the difference in bone dimensions in the two groups, the stiffness (ie loss of elasticity) in group B became significantly greater than that in group A (p = 0.024). The force needed to break the bone (F-max) was significantly higher in group A, than in group B (p = 0.024) and remained so after correction, although no longer significantly. In Group B, the diminution of the trabecular bone volume, in relation to tissue volume (BV/TV) and the increase in the degree of trabecular interconnection (TBPf) indicated osteoporosis, and focal osteoporosis of the metaphyseal spongy bone was seen on microscopy.

CONCLUSION

Experimentally induced prolonged Mg deficiency causes osteoporosis in rats.

Dementia in patients undergoing long-term dialysis: aetiology, differential diagnoses, epidemiology and management

Dementia in patients undergoing long-term dialysis has not been clearly defined; however, four different entities have been described. Uraemic encephalopathy is a complication of uraemia and responds well to dialysis. Dialysis encephalopathy syndrome, the result of acute intoxication of aluminium caused by the use of an aluminium-containing dialysate, was a common occurrence prior to 1980. However, using modern techniques of water purification, such acute intoxication can now be avoided. Dialysis-associated encephalopathy/dementia (DAE) is always associated with elevated serum aluminium levels. Pathognomonic morphological changes in the brain have been described, but the mechanism for the entry of aluminium into the CNS is incompletely understood. The mechanisms involved in the pathogenesis of the neurotoxicity associated with aluminium are numerous. Although only a very small fraction of ingested aluminium is absorbed, the continuous oral aluminium intake from aluminium-based phosphate binders, and also of dietary or environmental origin, is responsible for aluminium overload in dialysis patients. Age-related dementia, especially vascular dementia, occurs in patients undergoing long-term dialysis as frequently as it does in the general population. The differential diagnoses of dialysis-associated dementias should include investigation for metabolic encephalopathies, heavy metal or trace element intoxications, and distinct structural neurological lesions such as subdural haematoma, normal pressure hydrocephalus, stroke and, particularly, hypertensive encephalopathy and multi-infarct dementia. To prevent DAE, dietary training programmes should aim to achieve the lowest phosphate intake and pharmacological tools should be used to keep serum phosphate levels below 2 mmol/L. To prevent vascular dementia, lifestyle modification should be undertaken, including optimal physical activity and fat intake, nicotine abstinence, and targeting optimal blood glucose, cholesterol and triglyceride levels, and blood pressure, to those outlined in current recommendations.

Primary hyperoxaluria type 1 causing end-stage renal disease in a 45-year-old patient

Primary hyperoxaluria type 1 (PH1) is caused by deficiency of peroxisomal alanine-glyoxylate aminotransferase which is in humans exclusively expressed in liver cells. The disease is inherited as an autosomal recessive trait, and initial symptoms usually occur in early childhood. Up to the age of 25 years, 90% of the patients are symptomatic, and many patients develop end-stage renal failure. Pronounced medical care is necessary in PH1 patients to prevent generalized oxalosis with complications due to bone disease and peripheral gangrene. The rather short survival of patients on hemodialysis is caused by sudden arrhythmias and heart block. As no dialysis procedure is able to remove the daily produced oxalate, early transplantation is mandatory. Our 45-year-old patient is remarkable on the basis of the late manifestations of PH1. The diagnosis was delayed by unspecific symptoms of nephrolithiasis with recurrent pyelonephritis. Clinical course and diagnostic cornerstones of primary hyperoxaluria are outlined. The principles of conservative treatment and experiences with dialysis and transplantation are discussed.

[Diagnosing magnesium deficiency. Current recommendations of the Society for Magnesium Research]

The cardiovascular risk increases with decreasing serum levels of magnesium, and this already at concentrations within the previous reference range (0.70-1.10 mmol/L). For this reason, the Society for Magnesium Research has updated its 1986 recommendations for the diagnosis of magnesium deficiency. The diagnosis is based on the patient's history, his clinical symptoms, and the results of clinical-chemical investigations of plasma/serum and urine. Further diagnostic methods used include the determination of ionized serum magnesium and the magnesium retention test. The optimal serum magnesium concentration is > 0.80 mmol/L.

Can one really measure magnesium deficiency using the short-term magnesium loading test?

OBJECTIVE

To compare a 1-h-version of a magnesium-loading-test (MLT) designed for outpatients in healthy controls with the 8-h standard; to establish the test in patients after renal transplantation prone to develop magnesium (Mg) deficiency; to correlate femur Mg-concentration and percentage retention of the given load.

DESIGN

Comparison of mean values from healthy controls with respective from the literature; a prospective, randomized, controlled 4-month study; an intra-individual correlation of Mg-serum values and loading-test data with femur-Mg concentrations.

SETTING

One centre study in a medical university; outpatients from the transplant unit; inpatients from the orthopedic unit.

SUBJECTS

Twenty-four healthy controls aged 36.7 +/- 7.4 years; 34 patients after renal transplantation (46.5 +/- 14.3 years); 41 patients with hip replacement therapy (63.9 +/- 18.6 years).

INTERVENTION

Baseline Mg values were measured by atomic absorption spectroscopy (AAS) in serum and urine. An intravenous Mg load with 0.1 mmol Mg-aspartate hydrochloride per kilogram bodyweight was given during 1 h. In 24 h-urine, the amount of excreted Mg was measured by AAS and the percentage retention of the given load calculated according to the formula: 1 - [Mg 24 h-urine/Mg test dose] x 100. Femur Mg was measured by AAS in a peace of the femur neck. Patients after renal transplantation were randomized after the first Mg load to either obtain daily 5 mmol Mg-aspartate hydrochloride per kilogram bodyweight, or placebo. Four months later a second loading-procedure was performed.

MAIN OUTCOME MEASURE

Serum Mg, percentage retention of the given Mg load (%Ret) and femur Mg concentration.

RESULTS

Mean serum Mg values were within the normal range. In controls, %Ret was -18 +/- 21 and not different from the literature. In the first MLT after renal transplantation, %Ret was 47 +/- 43. In patients under Mg medication it decreased significantly to 16 +/- 26, but was 58 +/- 27 in the placebo group. Femur Mg concentration was 62.6 +/- 20.9 mmol kg-1 dry substance and the corresponding %Ret was 14 +/- 28 with r = - 0.7093.

CONCLUSION

The short-term version of the MLT is as good as the standard and was easily applied in outpatients. The indication from the good correlation between bone-Mg and %Ret and a marked decrease in %Ret in patients after Mg medication was that one can really measure magnesium deficiency.

[Calciphylaxis of the skin as a sequela of terminal kidney failure. Report and discussion of 3 cases]

Calciphylaxis is a rare syndrome mostly affecting patients with secondary hyperparathyroidism and in some cases with functional protein C or protein S deficiency. Skin lesions begin as superficial painful patches that progress to deep necrotic lesions. The findings are often misdiagnosed as livedo vasculitis and the prognosis is poor. Histopathologically, calcification in the media of small arteries and arterioles with intimal hyperplasia is seen. It is unclear if this morphologic hallmark is pathogenetic. Therapeutically, the calcium-phosphate product should be lowered pharmacologically by an intensified and modified dialysis treatment and parathyroidectomy.

[A long-term organic brain syndrome and brain stem symptoms in an undiagnosed dialysis-associated encephalopathy]

HISTORY AND CLINICAL FINDINGS

A 73-year-old woman in renal failure for the past 22 years had been on haemodialysis for 16 years. Because of hyperphosphataemia and peptic ulcers she had been on aluminium-containing antacids with a total intake over time of about 8 kg "pure" aluminium. Over the past 11 years she had biphasic symptoms of death anxieties and depression. She also had amnesic aphasia and some extrapyramidal symptoms as well as generalized convulsive seizures and recurrent falls.

INVESTIGATIONS

Cranial computed tomography merely revealed signs of a microangiopathy and an age-related decrease in brain volume. The EEG showed intermittent changes while the CSF and ECG were unremarkable. There was no benzodiazepine or ethanol in the blood.

TREATMENT AND COURSE

After excluding stroke with secondary epilepsy, uraemic encephalopathy was assumed to be the cause of the severe organic psychiatric syndrome. In the last few days before her death the patient had disturbance of consciousness and of breathing. She died during grotesque tossing movements, thought to be due to a brain stem stroke. Autopsy revealed high-grade myocardial hypertrophy caused by the hypertension, contracted kidney of vascular cause, hyperplasia of the parathyroid and calcification of the renal parenchyma as a sign of secondary parathyroidism. The CNS showed severe dialysis-associated encephalopathy with characteristic argyrophilic, aluminium-induced lysosomal intracytoplasmic inclusions in the choroid plexus epithelium, cortical glia and numerous neuron populations. Laser microprobe mass analysis (LAMMA) confirmed manifold increase in subcellular aluminium content, especially in the neuronal cytoplasm, also demonstrated by atom absorption spectrometry. Additional distinct deposition of beta A4-amyloid, typical of Alzheimer's disease, was probably age-related rather than associated with the dialysis and the aluminium uptake.

CONCLUSION

Dialysis-associated encephalopathy must be taken into account as a possible cause of aetiologically uncertain neuropsychiatric symptoms in patients on chronic haemodialysis.

[Acute renal failure in IgM plasmocytoma with hyperviscosity syndrome]

HISTORY AND CLINICAL FINDINGS

Two days after starting withdrawal treatment for alcohol and drug abuse a 56-year-old woman developed acute renal failure. The patient was in a poor general condition and disoriented as to time and place. She had uraemic oral fetor and leg oedema. She had previously fractured both arms 3 months before.

INVESTIGATIONS

Biochemical tests indicated renal failure: creatine 1791 mumol/l, urea 51.7 mmol/l, potassium 5.3 mmol/l, phosphate 1.86 mmol/l. Serum protein electrophoresis suggested paraproteinaemia with M gradients in the gamma-fraction. Immune fixation electrophoresis demonstrated monoclonal IgM gammopathy of kappa-type (IgM 44.1 g/l). Haemoglobin level was reduced to 66 g/l. Bone marrow biopsy showed replacement of normal haematopoiesis by highly atypical plasma cells (> 30% of cell population). Magnetic resonance imaging revealed diffuse changes in the pelvis and vertebrae suggesting plasmacytoma, confirming the diagnosis of IgM plasmacytoma of kappa-type.

TREATMENT AND COURSE

Focal neurological symptoms (e.g. intermittent anisocoria and visual disturbances) suggested a hyperviscosity syndrome, although the serum protein level was nearly normal. Plasma viscosity was 2.2 mPas (normal range 1.2-1.38 mPas), lowered to 1.5 mPas by plasmapheresis, after which the neuropsychiatric symptoms improved. Chemotherapy for the plasmacytoma in stage IIIB was initiated (VAD scheme) and dialysis became necessary for terminal renal failure.

CONCLUSION

Due to the raised level of IgM protein level and its high molecular size a hyperviscosity syndrome with paraproteinemic coma may occur, even though total plasma protein is nearly normal.

Pentoxifylline, cyclosporine A and taurolidine inhibit endotoxin-stimulated tumor necrosis factor-alpha production in rat mesangial cell cultures

Tumor necrosis factor-alpha (TNF-alpha) is an important mediator in the pathogenesis of glomerular disease. Intrinsic glomerular cells as well as extraglomerular cells have been found as a source of TNF-alpha. Rat glomerular mesangial cells produce TNF-alpha after stimulation with bacterial lipopolysaccharide (0.1, 1.0 and 10 microg/ml) over different times (4, 8, 16 and 24 h). We show that lipopolysaccharide-induced production of TNF-alpha in rat mesangial cell cultures is inhibited by pentoxifylline (50 mg/ml), cyclosporine A (0.1 microg/ml) and taurolidine (100 mg/ml). Inhibition of this production seems to be a promising treatment option for renal disease. Already pentoxifylline and cyclosporine A have been shown to improve different glomerular pathologies. Their in vitro effect on TNF-alpha production shown here might influence this.

Correlation of drug-related aluminum intake and dialysis treatment with deposition of argyrophilic aluminum-containing inclusions in CNS and in organ systems of patients with dialysis-associated encephalopathy

CNS tissue and peripheral organs of 50 autopsy cases with chronic renal failure (CRF) and dialysis treatment were evaluated for aluminum- (Al) containing argyrophilic inclusions using the Howell and Black method modified by Reusche. Morphological alterations were correlated with the duration of hemodialysis (HD) and to the amount of prescribed Al-containing drugs for better control of hyperphosphatemia. Significant correlations were found between the degree of morphological alterations and Al intake up to 2.5 kg (p = 0.0003), as well as for morphology and duration of longterm HD up to 178 months (p = 0.001). Most sensitive structure for CNS deposits were choroid epithelia, followed by glial cells and neurons. Autonomic ganglia, heart, ovary/testis, parathyroid, adrenal, and pituitary demonstrated reliably peripheral deposits. Al-containing drugs, administered preferentially during HD, explain the additional significance of Al uptake and duration of dialysis (R-Qu. = 0.6697). The deposition of Al-containing proteinaceous inclusions is apparently irreversible. After renal transplantation, with termination of drug-related Al intake and normalized renal Al excretion, the Al-induced argyrophilic degradation products remained in the cellular cytoplasm in unchanged fashion up to 10 years.

Renin immunochemistry, sodium excretion and relative heart weight in cyclosporine- or alimentary-induced magnesium deficiency in rats

Rats were given a magnesium-(Mg) depleted (Mgd), or a Mg-standard (Mgst) or a Mg-enriched (Mge) diet, with 20 mg/kg/day cyclosporine (Cy) or olive oil per os for 90 days (6 groups). Anti-renin antibody was applied and the percent of renin-positive glomeruli (RI) was taken. Sodium excretion (NaU), relative heart weight (HW), as a measure of hypertension, and total femur Mg were measured. Compared to dietary controls, femur Mg was reduced under Cy and Mgd or Mgst indicating Mg deficiency. RI was higher in all Cy groups (p < 0.01), and Nau was lower in Mgd + Cy and in Mgst + Cy (p < 0.01). Correspondingly, HW was found to be significantly higher in Mgd + Cy and Mgst + Cy. In animals under Mge + Cy, there were no differences in NaU and HW compared to controls. The results indicate a relation between Cy-related hypertension and Mg status: Mg deficiency seems to enhance the hypertensive effect of Cy via sodium retention.

Magnesium metabolism: basic aspects and implications of ciclosporine toxicity in rats

In rapidly growing male Sprague-Dawley rats with an initial body weight of 100 +/- 10 g, we investigated how alimentary magnesium (Mg) supply, Mg metabolism and ciclosporine (Ci)-associated nephrotoxicity are interrelated. Food with 100 ppm Mg (1Mg) or 1,000 ppm Mg (stMg) or 10,000 ppm Mg (rMg), Ci 20 mg/kg body weight daily or olive oil were applied for 3 months (n = 10/group). Mg concentrations in various compartments were measured by atomic absorption spectrophotometry. Creatinine clearance (Jaffe), urinary N-acetyl-beta-D-glucosaminidase (NAG) activity (fluorometrically), urinary sodium excretion (flame photometry) and osmolality were measured. Histomorphological examination was done and renal renin expression was studied by monoclonal antibodies. Ci reduced the Mg concentration of the femur under 1Mg (72.6 +/- 9.7 vs. 112.6 +/- 14.3 mmol/kg dry substance, p < 0.05) and under stMg (150.6 +/- 16.6 vs. 194.1 +/- 10.2 mmol/kg dry substance, p < 0.05), thus indicating Ci-related Mg deficiency. This was due to a significant increase in Mg excretion in Ci treatment compared to dietary controls. Under rMg, there was no difference between Ci-treated and control animals. Ci treatment lowered creatinine clearance in 1Mg (1.42 +/- 0.05 vs. 3.02 +/- 0.58 ml/min) and in stMg (1.04 +/- 0.45 vs. 2.18 +/- 0.51 ml/min), NAG/creatinine and urinary sodium excretion were negatively affected by Ci under 1Mg and stMg. Histomorphology showed macrocalcifications due to Mg deficiency and Ci-specific findings, which were markedly enhanced in 1Mg and stMg. Animals with plentiful Mg supply had no functional alterations due to Ci and no or weakly expressed histomorphological lesions. Renin-positive stained cells were higher in Ci-treated animals. This seems to be functionally relevant under 1Mg and stMg, since it was associated with sodium retention and elevated relative heart weight, indicating hypertension. Alimentary or drug-induced Mg deficiency plays a relevant role in the pathophysiology of chronic Ci nephrotoxicity. Our data suggest that Mg supplementation is helpful to reduce Ci toxicity, even if there is 'normal' alimentary Mg intake.

[Intestinal vasculitis and glomerulonephritis in hepatitis C- associated cryoglobulinemia]

In a 53-year-old female patient with recurrent, sometimes bloody diarrhea, the long standing diagnosis of an ANA-negative lupus erythematosus with membranoproliferative glomerulonephritis, leucocytoclastic vasculitis and chronic hepatitis was ruled out and the diagnosis of a hepatitis C associated cryoglobulinaemia was established. The origin of the diarrhea was due to intestinal vasculitis as a result of cold food or beverages.

Magnesium metabolism in erythrocytes of patients with chronic renal failure and after renal transplantation

Plasma and erythrocyte Mg2+ concentrations were found to be increased in 14 haemodialysis patients with chronic renal failure and in 7 chronic renal failure patients receiving chronic ambulatory peritoneal dialysis. The rate of Na+/Mg2+ antiport was significantly higher in haemodialysis patients, but not in chronic ambulatory peritoneal dialysis patients (control: 0.15 +/- 0.02, haemodialysis: 0.46 +/- 0.08, chronic ambulatory peritoneal dialysis: 0.21 +/- 0.06; Mg2+, mmol/30 min x 1 cells). High erythrocyte Mg2+ content in chronic renal failure results from the increased plasma Mg2+, which induces elevated Mg2+ uptake during haematopoiesis. An increased rate of Na+/Mg2+ antiport, which only performs Mg2+ efflux, leads to a relatively lower erythrocyte Mg2+ content in haemodialysis patients compared with chronic ambulatory peritoneal dialysis patients. The elevated Na+/Mg2+ antiport in erythrocytes from haemodialysis patients was almost normalised after haemodialysis. Incubation of normal erythrocytes with heat-inactivated plasma from haemodialysis patients led to a doubling of Na+/Mg2+ antiport, indicating the presence of a heat-stable, dialysable plasma factor. This factor does not accumulate in chronic ambulatory peritoneal dialysis patients. After renal transplantation all changed quantities of Mg2+ metabolism returned to normal.

Diagnosis of renal transplant failure by real-time and duplex Doppler sonography

A total of 419 real-time and duplex Doppler ultrasound examinations of renal allografts were carried out in 61 patients. Results were related to the clinical diagnoses based on histomorphological, clinical, and laboratory findings. The results of all sonographic examinations in terms of the diagnostic parameters of normal function, acute tubular necrosis, and interstitial and vascular rejection did not yield reliable criteria for distinguishing between the different forms of transplant dysfunction. The maximum difference was calculated for each ultrasound parameter between a time of normal transplant function and at a time of dysfunction. By means of this 'maximum parenchyma-pyelon index difference' it was possible to discriminate between acute tubular necrosis and vascular rejection (P < 0.05). Acute tubular necrosis could be distinguished from interstitial rejection using the maximum longitudinal renal diameter difference and the maximum parenchyma-pyelon index difference (P < 0.05). To discriminate between interstitial and vascular rejection the maximum pulsatility index difference was very useful (P < 0.05). Combined real-time and duplex Doppler sonography is most valuable in the diagnosis of transplant failure when it is performed not only in the case of dysfunction but also when transplant function appears to be normal.

[Extrathoracic prolapse of the pulmonary parenchyma after a bout of coughing with spontaneous serial rib fractures]

A 54-year-old man with an feverish infection of the lower respiratory tract developed severe pain in the lateral and basal part of the left thorax after a severe coughing bout. A haematoma occurred at the site and it looked as though tissue evaginated at that spot on coughing and pressing. The clinical diagnosis was pneumonia and abnormal mobility of the eighth to tenth rib on the left with crepitations. The chest radiograph demonstrated fractures of these ribs and extrathoracic sickle-shaped collection of air in the left laterobasal area. Computed tomography additionally showed prolapse of pulmonary tissue on pressing. This was thus a case of "cough fracture", complicated by herniation of lung tissue. There was no evidence of incarceration of lung tissue and, as the patient was very obese, surgery was not indicated. Symptoms and signs of infection regressed on symptomatic and antibiotic treatment. The rib fractures healed as pseudoarthroses. Lung tissue prolapse on pressing was still present 3 months later.

Follow-up study of renal transplants by duplex Doppler and gray-scale ultrasound

In the early postoperative period after renal transplantation 388 follow-up ultrasound examinations were performed in 77 patients. Over a period of 18 months standardized duplex indices (resistive index, pulsatility index) and gray-scale parameters (parenchyma/sinus index; medulla/cortex index) were sampled. These data were correlated retrospectively with clinical and pathological diagnoses. To delineate the individual course of duplex and gray-scale indices during different transplant diseases we created a new parameter: the MID (maximal index difference) which is a result of the difference between the highest index during the phase of renal dysfunction and the lowest index during the phase of normal renal function. This MID, calculated for duplex indices and for the parenchyma/sinus index, indicated significant differences in the behavior of renal transplants during the four main diseases: interstitial rejection, vascular rejection, acute tubular necrosis and Cyclosporine A nephrotoxicity. Using the MIDs, a table of cut-off values was established, which enables to differentiate retrospectively these four transplant complications with a sensitivity of 84% and specificity of 81%. In our opinion consequent follow-up examinations with duplex and gray-scale sonography should be performed, enabling sonography to become a helpful diagnostic instrument in the monitoring of renal transplants.

Theophylline and magnesium inhibit the contraction elicited with ciclosporin and angiotensin II in mesangial cell cultures

One serious side effect of ciclosporin (CS) therapy is its acute nephrotoxicity characterized by a marked decrease in glomerular filtration rate (GFR). A main determinant of GFR is the ultrafiltration coefficient which is thought to be regulated by the contractile state of the cells of the mesangium. CS enhances contractions of mesangial cells elicited with angiotensin II. By way of a lowered ultrafiltration coefficient this effect of CS may be partly responsible for its acute nephrotoxicity. We have therefore examined the effect of compounds that may attenuate the enhanced contractile response of the smooth-muscle-like mesangial cells. Prostaglandin E2 (10(-8)-10(-5) mol/l) and dibutyryl cyclic AMP (10(-4) mol/l) reduced the number of contracting cells from more than 50% to about 10%. The clinically used agent theophylline (10(-5) g/ml) decreased the number of contractions of CS-pretreated mesangial cells from 80.0 to 28.4% (p less than 0.001). Additionally, a marked decrease in the percentage of contractions (83.3 to 33.3%; p less than 0.001) was observed when the concentration of magnesium chloride was elevated from 0 to 2 mmol/l. The finding that the enhanced contractile response of CS-pretreated mesangial cells can be overcome by theophylline and/or high magnesium levels may be of clinical interest with a view to acute CS nephrotoxicity.

[Studies on cultured rat mesangial cells using cyclosporin A and magnesium--is magnesium nephroprotective in cyclosporin A therapy?]

One serious side effect of Cyclosporine A therapy is its acute nephrotoxicity characterized by a marked decrease in the glomerular filtration rate. A main determinant of the glomerular filtration rate is the ultrafiltration coefficient which is thought to be regulated by the contractile state of the cells of the mesangium. Cyclosporine A enhances contractions of mesangial cells elicited with angiotensin II. By way of lowered ultrafiltration coefficient this effect of Cyclosporine A may be partly responsible for its acute nephrotoxicity. Hypomagnesaemia is often associated with Cyclosporine A therapy. Profound tubular magnesium wasting by Cyclosporine A has been claimed its cause. We have investigated the effect of low and high magnesium concentration on the contractility of mesangial cells pretreated with Cyclosporine A. Without magnesium 80% of the cells contracted upon addition of angiotensin II. A marked decrease in the contractility was seen when the magnesium concentration was elevated to 2 mmol/l (34%). From these observations we conclude that magnesium serum levels even in the high normal range might be protective against the decrease of the glomerular filtration rate seen with CsA therapy.