Immunosuppressive Therapy of Antibody-Mediated aHUS and TTP

The recent classification of pediatric thrombotic microangiopathies (TMA) takes into consideration mechanisms of disease for guidance to targeted therapies. We present our experience with seven patients with antibody mediated atypical hemolytic uremic syndrome (aHUS) and thrombotic thrombocytopenic purpura (TTP). Five children had aHUS with antibodies against complement factor H (CFH-ab) and two with TTP with antibodies against metalloproteinase ADAMTS13. In the aHUS cases diagnosed and treated before the eculizumab era, CFH-ab was detected using the ELISA assay. Mutational analysis of selected complement genes was performed. TTP was diagnosed if, in addition to microangiopathic hemolytic anemia and thrombocytopenia, ischemic organ involvement and severe deficiency in ADAMTS13 activity were present. Treatment protocol consisted of plasma exchanges (PE) and steroid pulses, followed by the combination of cyclophosphamide and rituximab to achieve long-term immunosuppression. Four patients with CFH-ab and the TTP patients with ADAMTS13 antibodies came into sustained remission. After a median follow-up of 11.7 (range 7.7-12.9) years without maintenance therapy, no disease recurrence was observed; nevertheless, six patients, two had hypertension and two had proteinuria as a late consequence. One patient, with late diagnosis of CFH-ab and additional genetic risk factors who was treated only with PE and plasma substitution, reached end-stage renal disease and was later successfully transplanted using eculizumab prophylaxis. In the cases of antibody-mediated TMAs, PE and early immunosuppressive treatment may result in sustained remission with preserved kidney function. Further data are needed to establish optimal treatment of anti-FH antibody-associated HUS.

De novo inflammatory bowel disease in children after solid organ transplantation

Összefoglaló. A gyulladásos bélbetegség (inflammatory bowel disease, IBD) incidenciája folyamatosan nő, etiológiája egyelőre ismeretlen. Kezelésében gyakran alkalmazunk immunszuppresszív, illetve immunmoduláns szereket. Egyes esetekben azonban szolidszerv-transzplantációt követően, folyamatos immunszuppresszív kezelés mellett is megfigyelhető de novo IBD kialakulása. Célunk az volt, hogy Klinikánk beteganyagából összesítsük azon eseteket, amelyekben szolid szerv (máj, vese, tüdő) transzplantációját követően de novo IBD alakult ki. A transzplantációt megelőzően szklerotizáló cholangitis miatt gondozott betegeket kizártuk. A Klinikánkon gondozott, szolid szerv transzplantációján (179 máj, 197 vese, 29 tüdő) átesett betegek közül 4 (2 máj- és 2 vesetranszplantált) gyermeknél alakult ki de novo IBD. A transzplantációhoz vezető alapbetegségek biliaris atresia, polycystás vese és Denys-Drash-szindróma voltak. A transzplantációt követő immunszuppresszív terápia mind a 4 esetben tartalmazott szisztémásszteroid- és takrolimuszkezelést, emellett 3 esetben mikofenolát-mofetil (MMF)-terápiát is. A kivizsgálást indikáló főbb tünetek a haematochesia, hasmenés, fáradékonyság és fogyás voltak. A családi anamnézis 1 esetben volt pozitív. A de novo IBD diagnózisának felállítását követően mind a 4 betegnél az addigi immunszuppressziós terápia módosításra került. Összességében elmondható, hogy a szolidszerv-transzplantációt követő de novo IBD kialakulása ritka, etiológiája tisztázatlan. Az irodalom felveti az alkalmazott immunszuppresszív szerek (takrolimusz és MMF), illetve infekciók etiológiai szerepét, de az is felmerül, hogy a de novo IBD olyan önálló entitás, mely elkülönül a klasszikus IBD kategóriáitól. Klinikai szempontból fontos a tünetek hátterében álló betegség tisztázása, hiszen a prezentációs tüneteknek megfelelő, a differenciáldiagnosztika során felmerülő egyéb betegségek terápiája merőben eltér. A megfelelő terápia hozzájárulhat a transzplantált betegek morbiditásának és mortalitásának csökkentéséhez. Orv Hetil. 2021; 162(18): 720-726. Summary. The incidence of inflammatory bowel disease (IBD) is increasing, however, the aetiology is still unknown. The therapy consists of immunosuppressants and immunomodulators. In some cases, despite the continuous immunosuppressant therapy, de novo IBD develops. Our aim was to evaluate patients diagnosed with de novo IBD after solid organ (liver, kidney, or lung) transplantation. Patients treated with sclerosing cholangitis prior to liver transplantation were excluded. 4 patients (two kidney and two liver transplants) were diagnosed with de novo IBD. The underlying diseases leading to transplantation were biliary atresia, polycystic kidney, and Denys-Drash syndrome. All patients received systemic steroid and tacrolimus treatment, and 3 patients (2 kidney and 1 liver transplant) also received mycophenolate mofetil (MMF). The main symptoms indicative of de novo IBD were haematochezia, diarrhoea, fatigue, and weight loss. Family history for IBD was positive in 1 case. Following the diagnosis of IBD, immunosuppressive therapy was modified. Overall, the development of de novo IBD following solid organ transplantation is quite rare, and its aetiology is unknown. According to the literature, immunosuppressants (tacrolimus and MMF) and infections play a role in the pathomechanism, but it seems that de novo IBD is a separate entity from the classical IBD categories. From a clinical point of view, it is important to elucidate the underlying disease of the symptoms, as the treatment of other diseases that arise during differential diagnosis according to the presentation symptoms is very different. Appropriate therapy can help reduce morbidity and mortality in transplant patients. Orv Hetil. 2021; 162(18): 720-726.

Ambulatory arterial stiffness index in children after kidney transplantation

Given the increase in CV morbidity after RTx and the scarcity of CV events in pediatrics, surrogate markers should be assessed to characterize CV damage in this population. AASI is a marker of arterial stiffness in adults, predicting cardio- and cerebrovascular morbidity. Our aim was to assess the determinants of AASI in RTx children (n = 54, 15.5 ± 3.5 yr) and to examine its relationship to central PWV. AASI was calculated from 24 h ABPM. PWV was determined by applanation tonometry, body composition by multifrequency bioimpedance measurement. The dipping state, volume overload, and time on dialysis were the main predictors of AASI (p < 0.05). Children with established HT (n = 34) had increased AASI, extracellular body water, and BNP (p < 0.05). In contrast to AASI, PWV did not differ between HT and normotensive RTx patient groups. There was no correlation between AASI and PWV. PWV was increased in children who spent more than one yr on dialysis prior to RTx. In conclusion, increased AASI in HT RTx children better characterizes the actual volume- and pressure-dependent arterial rigidity rather than long-term morphological changes in large arteries as reflected by PWV.

Post-transplant diabetes mellitus in children following renal transplantation

PTDM plays a role in chronic allograft nephropathy and decreases graft and patient survival. Considering the serious outcome of chronic hyperglycemia, the importance of early recognition and the few data in children, in this retrospective analysis we studied the characteristics and risk factors of PTDM in 45 pediatric renal transplant recipients receiving Tac or CyA-based immunosuppression. Fasting blood sampling and OGTT were performed. PTDM has been developed in six patients (13%), while seven children (16%) had IGT, with the overall incidence of a glucose metabolic disorder of 29% in pediatric renal transplants. Patients in the PTDM + IGT group were younger and had higher systolic blood pressure and serum triglyceride level than children with normal glucose tolerance. Multivariate analysis identified Tac treatment, Tac trough level, steroid pulse therapy and family history of diabetes to be associated with the onset of PTDM. In pediatric renal transplants, OGTT and frequent assessment of blood glucose levels might be essential not only in the post-transplant management, but also prior to transplantation, particularly with family history of diabetes. Careful monitoring and modified protocols help to minimize the side effects of Tac and corticosteroids.

Effect of propranolol on heart rate variability in patients with end-stage renal disease: a double-blind, placebo-controlled, randomized crossover pilot trial

BACKGROUND

Low heart rate variability (HRV) is an independent risk factor of cardiac mortality in patients with end-stage renal disease (ESRD). It has been explained by uremic parasympathetic neuropathy. Sympathetic overactivity can also reduce HRV. Our aim was to determine whether there is vagal activity in ESRD patients that is masked by sympathetic activity.

METHODS

The effect of propranolol on HRV was examined in 13 patients with ESRD, aged 20.1 +/- 7.6 years without diabetes. All patients were given intravenous propranolol (0.05 mg/kg) once and placebo once in a randomized, double-blind way, with an interval of 6.6 days (mean, range: 2-9). Propranolol was administered before hemodialysis treatment, after 40 minutes supine resting period. HRV was registered for 10 minutes, during supine, before and after the injection. Patients' HRV data were compared to that of 29 age-matched healthy controls.

RESULTS

Initially, both high-(HFV) and low-frequency (LFV) bands of heart rate variability were lower in ESRD patients compared to controls (p < 0.001 for both). Propranolol resulted in a significant increase of HFV (propranolol: AlgHFV = 0.182 (0.027 - 0.337), placebo: deltalgHFV = -0.029 (-0.128 - +0.070); p = 0.032). Elevation of LFV was not significant. Six patients had an elevated plasma norepinephrine and/or epinephrine level. Plasma dopamine level was elevated in all but 1 patient (mean: 432 pmol/l, 95% CI: 320-543) and showed an inverse relationship with the increase of IgHFV secondary to propranolol (r = -0.66, p = 0.014).

CONCLUSIONS

Low HFV of ESRD patients can be improved by beta-adrenergic blockade. It demonstrates that there is some vagal activity in ESRD that is masked by sympathetic activity. Therefore, altered sympathovagal balance of ESRD patients should be taken into consideration in the assessment of vagal uremic neuropathy.

Autonomic dysfunction in uremia assessed by heart rate variability

Decreased heart rate variability is an independent risk factor for cardiac mortality in hemodialysis patients. Our aim was to determine whether it is already present in uremic children and young adults on hemodialysis and following renal transplantation. Twenty-two hemodialysis patients [age 17.2 years (median, quartiles 13.0-22.6)], 22 transplant patients [18.4 years (14.4-21.2)], and 29 healthy controls [16.4 years (15.7-21.1)] were examined. Heart rate and its high (HF) and low (LF) frequency variability were measured in the supine position for 10 min. High and low frequency variability was significantly reduced, whereas heart rate and LF/HF ratio was significantly elevated in both patient groups compared with controls. There was a clear-cut difference between the dialyzed and the transplanted groups based on the HF variability, with the lowest values in the dialysis group ( P<0.01). LF and LF/HF data did not allow us to distinguish between the patient groups. In conclusion, heart rate variability in the HF range is a sensitive tool for detecting cardiovascular autonomic dysfunction that is already present in children and adolescents with impaired kidney function.

Signs of autonomic neuropathy in childhood uremia

To evaluate the presence of autonomic neuropathy in childhood uremia, cardiovascular autonomic reflexes were examined in children with chronic renal failure. Cardiovascular autonomic reflexes of 10 uremic patients on chronic dialysis and 10 transplanted patients were compared to assess the effect of transplantation on autonomic neuropathy. Resting heart rate, heart rate changes induced by deep breathing, by Valsalva maneuver, and following standing up, and blood pressure change induced by handgrip test were examined. Of the 10 uremic children, 4 showed early involvement and 2 had definite involvement of autonomic neuropathy. Only 1 of the 10 transplanted patients showed early signs of autonomic neuropathy. Autonomic tests demonstrated predominantly parasympathetic dysfunction. In conclusion, cardiovascular autonomic neuropathy is not rare in children and adolescents and young adults with chronic renal failure. In contrast, the prevalence is very low in transplanted patients with similar uremic precedents. Efforts should be made to prevent or delay this uremia-related complication.

Monitoring cardiovascular changes during hemodialysis in children

Hemodialysis (HD) causes rapid volume shifts and circulatory changes. In chronic renal failure (CRF) Na+/K+ATP-ase is depressed, whereas endogenous digoxin-like factor (EDLF) is elevated. Our aim was to characterize HD-induced cardiovascular adaptation and its possible links to Na+/K+ATP-ase and EDLF. Eleven children with CRF on HD (aged 14.7 +/- 3.7 years) and 11 healthy children were investigated for basic circulatory parameters. Thoracic impedance (Zo) and circulatory parameters were monitored by impedance cardiography (ICG) during HD. Erythrocyte Na+/K+ATP-ase and EDLF were measured before and after HD. Up to the loss of 6% of total body weight, Zo rose linearly with fluid removal, above this no further increase occurred. Heart rate and mean arterial pressure (MAP) were inversely related (r = -0.97); MAP rose in the first and decreased in the second part of HD. Systemic vascular resistance paralleled MAP, whereas stroke volume rapidly decreased, but stabilized in the second part of HD. The ratio of preejection period/ventricular ejection time (PEP/VET) correlated positively with HD duration (r = 0.92), suggesting diminished cardiac filling. Cardiac index (CI) remained stable. EDLF was high in uremia accompanied by depressed Na+/K+ATP-ase (P < 0.05 and P < 0.01, respectively). Following HD Na+/K+ATP-ase normalized. Correlation between Na+/K+ATP-ase activity and MAP was linear (r = 0.85). In conclusion, ICG during HD provides detailed information concerning circulatory adaptation resulting in stable CI, suggesting that the dialysis-induced hypovolemia is compensated by the centralization of the blood volume. Changes of Na+/K+ATP-ase indicate that dialyzable blood pressure-regulating substance(s) inhibit(s) the pump. However, lack of further correlation between Na+/K+ATP-ase, EDLF, and cardiovascular parameters indicates the complexity of the regulatory processes.

Bone metabolism and mineral density following renal transplantation

AIM

To study bone turnover following renal transplantation using a panel of biochemical markers and to correlate the results with both areal and volumetric bone mineral density (BMD).

PATIENTS

A total of 31 patients aged 18.1 years were transplanted 5.4 years before this study. Control patients (n = 31) were age and gender matched.

METHODS

In addition to measurement of biochemical markers, BMD was measured by single photon absorptiometry and peripheral quantitative computed tomography on the non-dominant radius.

RESULTS

Patients had reduced glomerular filtration rate, raised concentrations of serum phosphate, serum procollagene type I carboxy terminal propeptide, osteocalcin, and serum procollagene type I cross linked carboxy terminal telopeptide. The differences were still significant if only patients with normal intact parathyroid hormone were considered. BMD single photon absorptiometry Z score for age was significantly decreased. Following standardisation for height the differences were no longer present. With volumetric techniques patients had normal trabecular but decreased cortical and total BMD compared to age matched controls, but there was no difference from height matched controls.

CONCLUSION

Markers of bone turnover are increased following renal transplantation. However, the biochemical analysis did not allow conclusions to be drawn on the bone mineral content. BMD single photon absorptiometry Z score corrected for height and BMD measured by quantitative computed tomography compared to height matched controls were normal in paediatric renal transplantation patients. Height matched controls should be used in both areal and volumetric BMD measurements in states of growth failure.

Sodium-lithium countertransport in children with nephrotic syndrome

The mechanisms of sodium retention in edema-forming minimal change nephrotic syndrome (MCNS) have not been completely evaluated. The aim of this study was to characterize the transmembrane sodium transport in nephrotic syndrome by measuring the erythrocyte sodium-lithium countertransport (SLC) in vitro. Eighteen children with MCNS were studied in the edema-forming state, and subsequently at the beginning of remission. Nephrotic children with edema retained sodium (10+/-12 micromol/day) and had a higher SLC [426+/-118 vs. 281+/-60 micromol/l red blood cells (RBC) per hour, P=0.003). The intracellular sodium concentration of nephrotics was 6.1+/-2.1 mmol/l RBC, which did not differ from that of controls (6.42+/-2.24, n=13). In remission sodium balance became negative (-30+/-21 mmol/day), and the SLC decreased but still differed significantly from control values (P=0.009). The intracellular sodium content decreased to 4.4+/-0.9 mmol/l RBC (P=0.002). There was a negative correlation between erythrocyte SLC and plasma albumin concentration (r=0.48, P=0.003), and urinary sodium excretion rate (r=0.66, P=0.001). In conclusion, erythrocyte SLC is high in the edema-forming state of childhood nephrotic syndrome and decreases with the onset of remission. A role for the SLC in the altered sodium homeostasis of nephrotic syndrome is suggested.

[Hepatitis G virus infection in hemodialyzed children and adults following kidney transplantation]

Recently, a new human virus hepatitis G virus was identified. The aim of the present study was to use a combination of the reverse transcription-polymerase chain reaction and a new test for antibodies to the viral envelope protein E2 to assess the prevalence of hepatitis G virus infection in sera of children and adults treated with hemodialysis or peritoneal dialysis as well as in sera of those who underwent renal transplantation. Hepatitis G virus RNA prevalence was higher in the shole group of patients with renal failure than in control group. The difference between hepatitis RNA prevalence in transplanted group and in control group was found to be significant. Anti-E2, which are is considered as an indicator of a past hepatitis G virus infection, were detected in the similar rate in the treated and control subjects. Time on hemodialysis was significantly longer in hepatitis G virus infected patients as compared to uninfected patients and all patients with hepatitis G virus RNA have a history of blood transfusions. Patients with renal failure treated with dialysis or subjected to renal transplantation are at increased risk of acquiring the hepatitis G virus infection. Higher rates of the hepatitis G virus RNA and similar prevalence of anti-E2 in patients with renal failure as compared to controls suggest that the rate of hepatitis G virus infection resolution in immunosuppressed patients with renal failure might be lower than in immunocompetent subjects.

In vitro effect of human recombinant growth hormone on lymphocyte and granulocyte function of healthy and uremic children

The recombinant human growth hormone (rhGH), currently used in supraphysiological doses to promote growth acceleration in chronic renal failure children (CRF), also has the ability to influence their impaired immune functions. The effect of human growth hormone on the lymphoproliferative response in vitro was analyzed in the peripheral blood lymphocytes of 25 healthy and 11 uremic children. In 72% of the uremic cases and in 60% of the healthy individual children the hormone increased the lymphoproliferation alone, and/or when used in combination with phytohaemagglutinine. The range of the effective hormone concentrations differed individually. Using semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) a great variation in the gene expression of growth hormone- (GH)-receptor in peripheral lymphocytes was detected. The respiratory burst activity of peripheral polymorphonuclear leukocytes (PMN) in vitro, in response to GH alone and when combined with suboptimal dose of phorbolester (PMA), was assessed by measuring luminol enhanced chemiluminescence in ten uremic and 18 healthy children. In six out of the ten of the CRF patients and in eight out of 18 of the healthy children the GH enhanced the oxidative burst activity of granulocytes provoked by a suboptimal dose of PMA. However, the effective doses (10, 50 and 300 ng/ml) and incubation times (0, 45 and 90 min) showed individual variations. Our data suggest that rhGH treatment in uremic children could be advantageous considering this population's enhanced susceptibility to bacterial, viral and fungal infections.

Changes of urinary enzyme activity after endoscopic treatment of vesico-ureteric reflux

The urinary enzymes Gamma Glutamyl Transferase (GGT), Alkaline Phosphatase (ALP), Leucine-Arylamidase (LAS), and Dipeptidyl-Peptidase-IV (DPP-IV) were measured before and after endoscopic treatment of vesico-ureteric reflux (VUR) in two groups of twenty children. Ten patients had undergone successful endoscopic corrective surgery for VUR, another 10 patients had unsuccessful endoscopic intervention. After successful treatment the activity of LAS in the urine did not change, but GGT, ALP and DPP-IV activity in the urine was 2-5 times higher than before treatment (P < 0.03 for all three enzymes). Considerable changes of urinary enzyme activity were not observed following unsuccessful endoscopic treatment. Our data and the literature are contradictory. However, this contradiction might be explained by the differences in urine sampling methods. Our patients received the same chemoprophylactic drug at the time of both urine samplings, a point not considered by other researchers. The extent of increase of enzyme activity after endoscopic treatment of VUR did not reach the level that would permit the use of investigated enzymes for screening, because the observed changes did not exceed the limits of the normal range.

[Changes in urinary enzyme activity following silicon therapy of vesico-ureteral reflux]

The urinary enzymes Gamma Glutamyl Transferase (GGT), Alkaline Phosphatase (ALP), Leucine-Arylamidase (LAS) and Dipeptidyl-Peptidase-IV (DPP-IV) were measured before and after endoscopic treatment of vesico-ureteric reflux (VUR) in two groups of twenty children's. Ten patients had undergone successful endoscopic corrective surgery for VUR, another 10 patients had unsuccessful endoscopic intervention. After successful treatment the activity of LAS in the urine did not change, but that of GGT, ALP and DDP-IV activity in the urine was 2-5 times higher than before treatment (P < 0.03 for all three enzymes). Considerable changes of urinary enzymes' activity were not observed following unsuccessful endoscopic treatment. Our data and the literature are contradictory. However this contradiction might be explained by the differences in urine sampling methods. Our patients received the same chemoprofilactic drug at the time of both urine sampling, a point not considered by other researchers. The extent of increase of enzyme activity after endoscopic treatment of VUR did not reach the level that would permit the use of investigated enzymes for screening, because the observed changes did not exceed the limits of the normal range.

[Molecular biological studies on patients with nephrogenic diabetes insipidus]

Nephrogenic diabetes insipidus is a rare, mostly X-linked recessive disorder characterised by renal tubular resistance to the antidiuretic effect of arginine vasopressin. The gene responsible for the X-linked nephrogenic diabetes insipidus, the G-protein-coupled vasopressin V2-receptor, has been localised on the Xq28 region. In this study four patients were investigated with molecular genetic methods. Diagnosis was based on clinical symptoms and lack of increase of urinary osmolality after administration of the arginine vasopressin, or the synthetic vasopressin analogue DDAVP. Three different mutations (C112R, N317K, W323S) were found in three patients, while no mutation was detected in the fourth patient. Since earlier histiocytosis X has been diagnosed in this patient, this patient has probably central diabetes insipidus. Although the main symptoms of the disease can be found in all patients, there are significant differences in the seriousness of the symptoms as well as in some other symptoms. The explanations might be the different mutations in the V2-receptor gene and the various other genetic and environmental factors; these findings provide further evidence that X-linked nephrogen diabetes insipidus results from defects in the V2-receptor gene.

Hepatitis G virus infection in children on dialysis and after renal transplantation

The aim of the present study was to use a combination of the reverse transcription-polymerase chain reaction and a new diagnostic test for antibodies against the viral envelope protein E2 to assess the prevalence of hepatitis G virus (GBV-C/HGV) infection in sera of Hungarian children on hemodialysis (HD) or peritoneal dialysis (CAPD), as well as in sera of renal transplant patients (RTx). The GBV-C/HGV RNA prevalence was significantly higher in the whole group of children with renal failure (18.5%) than in the control group (children with urinary tract infection, 2.5%). The difference between the GBV-C/HGV RNA prevalence in the RTx group (33.3%) and in the control group (2.5%) was significant (P = 0.007). Anti-E2, which is considered an indicator of a past GBV-C/ HGV infection, was detected in 10% (1/10) of HD patients, in 33.3% (4/12) of RTx patients, but in none of the children on CAPD. These differences were not significant. Children receiving a renal graft are at an increased risk of developing GBV-C/HGV infection, which may be attributed to the immunosuppressive drugs necessary to maintain the grafts.

Sodium transport and bone mineral density in hypercalciuria with thiazide treatment

Erythrocyte sodium-potassium (Na+/K+)-ATPase and sodium-lithium (Na+/Li+) countertransport activities were measured in 18 children (aged 9.6 years, range 6-16 years) with idiopathic hypercalciuria (IHU) to evaluate cellular Na handling. The effect of chronic thiazide administration on these parameters and on bone mineral density was also evaluated. Patients with IHU had significantly lower erythrocyte Na+/K+-ATPase activity than 23 age-matched healthy controls (mean +/- SEM 2,156 +/- 110 micromol P/l erythrocyte per hour vs. 3,165 +/- 175, P < 0.01). Thiazide treatment significantly lowered urinary calcium excretion; this was followed by a slight suppression of intact parathyroid hormone (iPTH). The urinary calcium/creatinine ratio before and during treatment was 0.90 +/- 0.07 mmol/mmol versus 0.51 +/- 0.06 respectively, P < 0.01. The corresponding iPTH levels were 5.9 +/- 0.6 pmol/l and 5.1 +/- 0.7, P < 0.05. The Na+/K+-ATPase activity increased significantly (2,769 +/- 169 micromol P/l erythrocyte per hour vs. 2,156 +/- 110 in the control period, P < 0.01) and the Na+/Li+ countertransport decreased (268 +/- 28 micromol Li/l erythrocyte per hour vs. 328+26 in the control period, P < 0.03). The bone mineral density Z score rose from -1.3 +/- 0.26 to -0.8 +/- 0.22 (P < 0.03). We conclude that IHU is accompanied by abnormalities of erythrocyte Na+/K+-ATPase and Na+/Li+ countertransport which are corrected by chronic hydrochlorothiazide administration. These changes could model alterations in renal tubular transport mechanisms still to be elucidated. Chronic thiazide treatment also has a positive effect on bone mineral density.

[Effect of dialysis on Na+/K+-ATP-ase activity in uremic children]

The enzyme Na+/K(+)-ATPase plays a central role in the regulation of transmembrane ionic transports. According to previous reports its activity decreased in uremic state. The activity of Na+/K(+)-ATPase in detergent pretreated erythrocytes was studied in seven uremic children prior to and following the hemodialysis (HD) session. Additionally, the level of endogenous digoxin like factors in the plasma (EDLF) was determined. Before the HD session the Na+/K(+)-ATPase activity decreased compared to the control value (mean +/- SD: 2078 +/- 527 vs 3245 +/- 362 nmol P/ml RBC/h, p < 0.01). Following HD it became normal (3366 +/- 952 nmol P/ml RBC/h, n.s.). Prior to the HD the EDLF level was higher, while after the HD no difference was noted from the control value (0.29 +/- 0.04, p < 0.05; 0.24 +/- 0.04 n. s. vs control; 0.21 +/- 0.04 ng/ml). Before the HD blood pressure was significantly elevated compared to the control (117 +/- 20/92 +/- 18 vs 95 +/- 2/64 +/- 2 Hgmm, p < 0.05). By the end of the HD it became normal (100 +/- 14/79 +/- 11, n.s.). Although no correlation was found between the EDLF level and Na+/K(+)-ATPase activity, a positive significant correlation was found between the changes of enzyme activity and the changes in the systolic (r = 0.83, p < 0.05) and diastolic (r = 0.82, p < 0.05) blood pressure during the HD. Our results indicate, that in uremic children the Na+/K+ pump is inhibited by a dialysable, blood-pressure regulator substance and so the enzyme activity elevates following the HD session. However, decreased blood pressure activates counterregulatory mechanisms, which-to lower extent-inhibit the activity of the pump.

Altered Na(+)-K+ ATPase activity in uraemic adolescents

The Na(+)-K+ ATPase enzyme plays an essential role in the regulation of cell composition and volume. Enzyme activity itself is regulated by substrate availability and several hormones. In adult uraemic patients red blood cell Na(+)-K+ ATPase activity is decreased. However, it is unknown if children with uraemia exhibit the same phenomenon. Therefore, in the present study we examined whether endogenous digoxin-like factors (EDLF) and physicochemical membrane properties play a role in the regulation of erythrocyte Na(+)-K+ ATPase activity in uraemic children and adolescents. Healthy age-matched children were used as controls. Enzyme activity was measured in detergent-pretreated red blood cells and erythrocyte ghosts. Na(+)-K+ ATPase activity (2204 +/- 538 nmol Pi ml erythrocyte-1 h-1 in detergent pretreated erythrocytes; 204 +/- 56 nmol Pi mg protein-1 h-1 in ghosts) in adolescents with uraemia was lower compared to controls (3245 +/- 362 nmol Pi ml erythrocyte-1 h-1; 266 +/- 37 nmol Pi mg protein-1 h-1, p < 0.001, p < 0.05, respectively). Plasma levels of EDLF were elevated in uraemic patients (0.30 +/- 0.05 versus 0.21 +/- 0.04 ng ml-1, p < 0.01). Furthermore, the membrane lipid component was decreased in patients with uraemia, while the cholesterol/phospholipid ratio and membrane fluidity were similar in both groups. No correlation was found between the decrease in Na(+)-K+ ATPase and the increase in EDLF concentration and altered membrane lipid components. Our results demonstrate, that similar to the findings of adults, the activity of Na(+)-K+ ATPase is diminished in uraemic adolescent patients, and that uraemia-associated elevation in EDLF and altered membrane components do not play a role in the down-regulation of Na(+)-K+ ATPase. Therefore other factors (presence of other inhibitors and/or reduced number of enzyme molecules) should contribute to the lower activity of the Na(+)-K+ pump.

[Normal values of calcium and oxalate excretion in children]

Aim of the study was to establish normal values for calcium/creatinine (Ca/cr) and oxalate/creatinine (Ox/cr) ratio in infants and children. Urine probes of 416 healthy children (25 infants aged 1-7 days and 391 children aged 1 month-14.5 years) were analysed. Oxalate was measured by ion-chromatography. Urinary Ca2+/cr was normally distributed, Ox/cr had log-normal distribution. Ca/cr was the lowest in the first days of life, the highest between 7 month-1.5 years (mean +/- SD = 0.39 +/- 0.28 mmol/mmol), a slight decrease could be observed until 14 years (0.34 +/- 0.18). The highest Ox/cr values were measured during the first month of life (geometric mean/range/ = 133 /61-280 mmol/mmol/), followed by gradual decrease until 14 years (25/6-73/). The measurement of Ca2+/cr and Ox/cr in first morning urine samples is suitable for screening of hypercalciuria and hyperoxaluria. The interpretation of the values requires age specific reference values. Both calcium and oxalate determinations should be the part of the evaluation of patients with hematuria, hypercalciuria or nephrolithiasis.

Urinary calcium and oxalate excretion in children

We have established normal values for calcium/creatinine (Ca/Cr) and oxalate/creatinine (Ox/Cr) ratios in 25 infants (aged 1-7 days) and 391 children (aged 1 month to 14.5 years) and compared these with values obtained in 137 children with post-glomerular haematuria and 27 with nephrolithiasis. Oxalate was measured by ion chromatography. Nomograms of Marshall and Robertson were used to calculate urine saturation to calcium oxalate. The Ca/Cr ratio was normally distributed whereas the Ox/Cr ratio had a log-normal distribution. The molar ratio of Ca/Cr was the lowest in the first days of life and the highest between 7 month and 1.5 years (mean +/- SD = 0.39 +/- 0.28 mmol/mmol). Following a slight decrease it stabilised by the age of 6 years (0.34 +/- 0.19 mmol/mmol). The highest Ox/Cr values were measured during the 1st month of life [geometric mean 133 (range 61-280) mumol/mmol], followed by a gradual decrease until 11 years of age [mean 24 (range 6-82) mumol/mmol]. Thirty-six haematuric children had hypercalciuria (26%), 23 had absorptive hypercalciuria, 13 renal type. Children with absorptive hypercalciuria on a calcium-restricted diet had significantly higher oxalate excretion than those with renal hypercalciuria and the control group [38 (range 28-49) vs. 22 (range 16-29) and 23 (range 22-27) mumol/mol respectively, P < 0.01]. Calcium oxalate urine saturation of stone patients was higher than that of patients with haematuria and the normal population (1.18 +/- 0.05 vs. 1.06 +/- 0.03, P < 0.03 and 0.84 +/- 0.03, P < 0.001 respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma amino acid concentration under human growth hormone treatment in uremic children

The plasma amino acid concentrations were investigated before and after 3 and 30 months of human recombinant growth hormone treatment in 7 children with chronic renal failure. The concentrations of amino acids in plasma showed characteristic changes (pretreatment vs. after 3 and 30 months of treatment): Lys 113 +/- 33 vs. 162 +/- 27 and 109 +/- 38 mumol/l, Met 21 +/- 8 vs. 31 +/- 4 and 16 +/- 5, Thr 105 +/- 23 vs. 148 +/- 60 and 118 +/- 30, Ala 455 +/- 109 vs. 536 +/- 93 and 314 +/- 60, Gln 298 +/- 66 vs. 277 +/- 52 and 544 +/- 65, Glu 168 +/- 46 vs. 209 +/- 57 and 96 +/- 24, Gly 345 +/- 137 vs. 479 +/- 169 and 342 +/- 95, Pro 378 +/- 148 vs. 422 +/- 28 and 527 +/- 229, OH-Pro 33 +/- 17 vs. 105 +/- 23 and 97 +/- 35, Se 133 +/- 39 vs. 178 +/- 55 and 131 +/- 12 mumol/l. Long-term treatment with human recombinant growth hormone normalized plasma alanine, glutamine, and glutamic acid levels, increased the OH-Pro concentration, and did not alter the amino acid ratios of Gly/Val, Phe/Tyr, Ser/Gly, and Asn/Asp, but the Gln/Glu ratio approached the normal value.

24 hour blood pressure monitoring in healthy and hypertensive children

24 Hour ambulatory blood pressure monitoring (ABPM) was performed to provide data on the normal daily blood pressure of healthy schoolchildren and on patients with hypertension. The subjects studied were 123 healthy schoolchildren with a mean (SD) age of 12.5 (1.6) years (range 9.5-14.5 years), 24 children with borderline or mild hypertension, 17 with renal hypertension and normal renal function, 10 with chronic renal failure, and six with a renal allograft. In eight children with definite renal disease a second measurement was performed after treatment modification. The monitor used for ABPM was validated with a mercury column manometer. The mean (SD) of the signed differences of the blood pressure measured by the two methods was -0.19 (1.75) mmHg for the systolic and -0.21 (2.11) mmHg for the diastolic blood pressure (n = 60). Normal values for daytime and night time blood pressure were determined for those aged 10-14 years. The mean (SD) blood pressure of the 123 children was 109 (7)/66 (8) mmHg (systolic/diastolic) for the daytime and 96 (8)/52 (7) mmHg at night time. Of the 24 children with borderline or mild hypertension 14 had a raised blood pressure on ABPM. The circadian rhythm was disturbed in three children of this group. Even children with normal daytime blood pressure had significantly higher systolic blood pressure in the night when compared with the controls. The incidence of disturbed circadian rhythm was higher in the groups with renal hypertension (4/17 in the subgroup with normal renal function, 5/16 in the group with renal failure and/or transplantation). All children undergoing a second ABPM measurement had a lower average blood pressure after treatment adjustment. ABPM measurements were reproducible and accurate. The method provided new data on the physiological circadian variation of blood pressure in healthy children. It proved to be a helpful tool in the diagnosis of hypertension, particularly in the detection of cases of disturbance of the circadian rhythm of blood pressure pattern and individual adjustment of treatment.

[Selective vitamin B12 absorption disorder (Imerslund-Gräsbeck syndrome)]

The authors present a case of Imerslund-Gräsbeck syndrome, i. e. a familial megaloblastic anemia with proteinuria. The disease is due to congenital, selective malabsorption of vitamin B12. The subnormal absorption of vitamin B12 is not altered by orally given intrinsic factor, but parenteral vitamin B12 therapy results in complete recovery. Approximately 150 cases have been described in literature, the authors' case is the first in Hungary.