Complement alternative pathway genetic variation and Dengue infection in the Thai population.

Dengue disease is a mosquito-borne infection caused by Dengue virus. Infection may be asymptomatic or variably manifest as mild Dengue fever (DF) to the most severe form, Dengue haemorrhagic fever (DHF). Mechanisms that influence disease severity are not understood. Complement, an integral component of the immune system, is activated during Dengue infection and the degree of activation increases with disease severity. Activation of the complement alternative pathway is influenced by polymorphisms within activation (factor B rs12614/rs641153, C3 rs2230199) and regulatory [complement factor H (CFH) rs800292] proteins, collectively termed a complotype. Here, we tested the hypothesis that the complotype influences disease severity during secondary Dengue infection. In addition to the complotype, we also assessed two other disease-associated CFH polymorphisms (rs1061170, rs3753394) and a structural polymorphism within the CFH protein family. We did not detect any significant association between the examined polymorphisms and Dengue infection severity in the Thai population. However, the minor allele frequencies of the factor B and C3 polymorphisms were less than 10%, so our study was not sufficiently powered to detect an association at these loci. We were also unable to detect a direct interaction between CFH and Dengue NS1 using both recombinant NS1 and DV2-infected culture supernatants. We conclude that the complotype does not influence secondary Dengue infection severity in the Thai population.

Construction of infectious dengue 2 virus cDNA clones using high copy number plasmid.

Procedures for cloning entire dengue serotype 2 virus genome in the multiple cloning site of a commercially available high copy number plasmid are described. The 10.7 kb viral RNA genome was reverse transcribed, amplified as three overlapping DNA fragments and successively ligated into pBluescript II KS, which contains the colE1 origin of replication. When propagated at room temperature (20-25 degrees C) under low level of antibiotic selection, the full-length recombinant plasmid was stable upon serial passages in two common Escherichia coli strains employed. Under the same culture conditions the whole dengue cDNA sequence was transferred successfully to another high copy number plasmid, pGem 3Z. Following in vitro transcription and lipofectin-mediated transfection, capped RNA transcripts derived from the plasmid initiated virus replication in C6/36 mosquito cells and BHK-21 cells within 3-4 days of transfection. Upon subsequent expansion in C6/36 cells, dengue viruses derived from the first- and eighth-plasmid passages achieved similar titers as the parent virus. They were also indistinguishable from the parent virus by the criteria of replication kinetics in mosquito and mammalian cell lines, and size and reactivity of selected viral proteins as detected with polyclonal and monoclonal antibodies. The cloning scheme and resultant recombinant plasmids based on high copy number cloning vectors allows greater flexibility in manipulation of dengue viral genome when compared with previous attempts employing low-copy number counterparts.

Autosomal recessive distal renal tubular acidosis associated with Southeast Asian ovalocytosis.

BACKGROUND: A defect in the anion exchanger 1 (AE1) of the basolateral membrane of type A intercalated cells in the renal collecting duct may result in a failure to maintain a cell-to-lumen H+ gradient, leading to distal renal tubular acidosis (dRTA). Thus, dRTA may occur in Southeast Asian ovalocytosis (SAO), a common AE1 gene abnormality observed in Southeast Asia and Melanesia. Our study investigated whether or not this renal acidification defect exists in individuals with SAO. METHODS: Short and three-day NH4Cl loading tests were performed in 20 individuals with SAO and in two subjects, including their families, with both SAO and dRTA. Mutations of AE1 gene in individuals with SAO and members of the two families were also studied. RESULTS: Renal acidification in the 20 individuals with SAO and in the parents of the two families was normal. However, the two clinically affected individuals with SAO and dRTA had compound heterozygosity of 27 bp deletion in exon 11 and missense mutation G701D resulting from a CGG-->CAG substitution in exon 17 of the AE1 gene. Red cells of the two subjects with dRTA and SAO and the family members with SAO showed an approximate 40% reduction in sulfate influx with normal 4,4'-di-isothiocyanato-stilbene-2,2'-disulfonic acid sensitivity and pH dependence. CONCLUSION: These findings suggest that compound heterozygosity of abnormal AE1 genes causes autosomal recessive dRTA in SAO.

Distal renal tubular acidosis and high urine carbon dioxide tension in a patient with southeast Asian ovalocytosis.

Southeast Asian ovalocytosis (SAO) is the best-documented disease in which mutation in the anion exchanger-1 (AE1) causes decreased anion (chloride [Cl-]/bicarbonate [HCO3-]) transport. Because AE1 is also found in the basolateral membrane of type A intercalated cells of the kidney, distal renal tubular acidosis (dRTA) might develop if the function of AE1 is critical for the net excretion of acid. Studies were performed in a 33-year-old woman with SAO who presented with proximal muscle weakness, hypokalemia (potassium, 2.7 mmol/L), a normal anion gap type of metabolic acidosis (venous plasma pH, 7. 32; bicarbonate, 17 mmol/L; anion gap, 11 mEq/L), and a low rate of ammonium (NH4+) excretion in the face of metabolic acidosis (26 micromol/min). However, the capacity to produce NH4+ did not appear to be low because during a furosemide-induced diuresis, NH4+ excretion increased almost threefold to a near-normal value (75 micromol/L/min). Nevertheless, her minimum urine pH (6.3) did not decrease appreciably with this diuresis. The basis of the renal acidification defect was most likely a low distal H+ secretion rate, the result of an alkalinized type A intercalated cell in the distal nephron. Unexpectedly, when her urine pH increased to 7.7 after sodium bicarbonate administration, her urine minus blood carbon dioxide tension difference (U-B Pco2) was 27 mm Hg. We speculate that the increase in U-B Pco2 might arise from a misdirection of AE1 to the apical membrane of type A intercalated cells.

Dengue virus infection of human endothelial cells leads to chemokine production, complement activation, and apoptosis.

Dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS) are severe complications of secondary dengue virus (DV) infection. Vascular leakage, hemorrhagic diathesis and complement activation are the hallmarks of the disease. The short-lived nature of the plasma leakage syndrome has led to the conclusion that altered permeability is most likely effected by a soluble mediator. In the present study, we show that infection of human endothelial cells with DV induces the transcriptional up-regulation and secretion of RANTES and IL-8 and, in the presence of anti-dengue Abs, the formation of nonlytic complement complexes. Extremely high levels of IL-8 were detected in plasma and pleural fluid samples from patients with DSS. Furthermore, DV infection of endothelial cells in vitro caused apoptosis. Complement activation, chemokine induction, and apoptotic cell death may act in concert to cause the fulminant but short-lived vascular leakage that is characteristic of DHF/DSS.

Renal tubular function in beta-thalassemia.

Studies of the renal involvement in thalassemic syndromes have been varied and few. This study was designed to define the renal abnormalities associated with beta-thalassemia and to correlate the renal findings with clinical parameters. One hundred and four beta-thalassemic children with various disease severity were studied. The patients were divided into three groups: 48 with severe anemia [hematocrit (Hct) < 25%], 31 on a hypertransfusion program and desferrioxamine treatment, and 25 with moderate anemia (Hct > 25%). The results were compared with 15 normal children. Significantly higher levels of proteinuria and low molecular weight proteinuria were found in all patients compared with normal children. Aminoaciduria was detected in one-third of patients. Thalassemic patients had significantly lower morning urine osmolarity, higher urine N-acetyl-beta-D-glucoseminidase and malondialdehyde (MDA, an indicator of lipid peroxidation). Patients with severe anemia had significantly higher low-molecular weight proteinuria and MDA, and lower urine osmolarity than those with moderate anemia. Our data confirmed the high frequency of renal abnormalities in beta-thalassemia patients and indicated some degree of proximal tubular dysfunction. Severity of the abnormalities correlated with the degree of anemia and were least severe in patients on hypertransfusion and desferrioxamine therapy. This suggested that the damage might be caused by anemia and increased oxidation induced by excess iron deposits.

Renal function in adult beta-thalassemia/Hb E disease.

Beta-Thalassemia hemoglobin E (beta-thal/Hb E) is the commonest form of hemoglobinopathy in Thailand. Shortened red cell life span, rapid iron turnover and tissue deposition of excess iron are major factors responsible for functional and physiological abnormalities found in various forms of thalassemia. Increased deposition of iron had been found in renal parenchyma of thalassemic patients, but no systematic study of the effect of the deposits on renal functions has been available. The purpose of this study is to describe the functional abnormalities of the kidney in patients with beta-thal/Hb E and provide evidence that increased oxidative stress might be one of the factors responsible for the damage. Urine and serum samples from 95 patients with beta-thal/Hb E were studied comparing with 27 age-matched healthy controls. No difference in the creatinine clearance was observed. beta-thal/Hb E patients excreted significantly more urinary protein (0.8+/-0.5 vs. 0.3+/-0.1 g/day, p < 0.001). Aminoaciduria was found in 16 % of the patients. Analysis of urinary protein by SDS-PAGE electrophoresis and silver staining revealed abnormal pattern of protein with increased small molecular weight (<45 kD) bands. Morning urine analysis showed significant lower urine osmolality (578.3+/-164.6 vs. 762.4+/-169.9 mosm/kg, p < 0.001) in patients. Patients excreted more NAG (N-acetyl beta-D-glucosaminidase, 26.3+/-41.3 vs. 8.4+/-3.9 U/g Cr, p < 0.0001) and beta2-microglobulin, 124.3+/-167 vs. 71+/-65.5 microg/g Cr, p = 0.001. Plasma and urine MDA (malonyldialdehyde) levels were both raised (p < 0.0001). Nine patients were selected for renal acidification study. All were found to be normal, but showed poor response to DDAVP challenge (urine osmolality 533+/-71). This is the first report of renal tubular defects found associated with beta-thal/Hb E disease. The mechanism leading to the damage is not known but it might be related to increased oxidative stress secondary to tissue deposition of iron, as indicated by the raised levels of serum and urine MDA. It is not known whether these functional defects would have any long-term effects on the patients. Further studies are warranted and means of prevention of these defects should urgently be sought.

Arrhythmogenic marker for the sudden unexplained death syndrome in Thai men.

BACKGROUND: Between 1981 and 1988, the Centers for Disease Control and Prevention reported a very high incidence of sudden death among young male Southeast Asians who died unexpectedly during sleep. The pattern of death has long been prevalent in Southeast Asia. We carried out a study to identify the clinical markers for patients at high risk of developing sudden unexplained death syndrome (SUDS) and long-term outcomes. METHODS AND RESULTS: We studied 27 Thai men (mean age, 39.7+/-11 years) referred because they had cardiac arrest due to ventricular fibrillation, usually occurring at night while asleep (n=17), or were suspected to have had symptoms similar to the clinical presentation of SUDS (n=10). We performed cardiac testing, including EPS and cardiac catheterization. The patients were then followed at approximately 3-month intervals; our primary end points were death, ventricular fibrillation, or cardiac arrest. A distinct ECG abnormality divided our patients who had no structural heart disease (except 3 patients with mild left ventricular hypertrophy) into two groups: group 1 (n=16) patients had right bundle-branch block and ST-segment elevation in V1 through V3, and group 2 (n=11) had a normal ECG. Group 1 patients had well-defined electrophysiological abnormalities: group 1 had an abnormally prolonged His-Purkinje conduction time (HV interval, 63+/-11 versus 49+/-6 ms; P=.007). Group 1 had a higher incidence of inducible ventricular fibrillation (93% for group 1 versus 11% for group 2; P=.0002) and a positive signal-averaged ECG (92% for group 1 versus 11% for group 2; P=.002), which was associated with a higher incidence of ventricular fibrillation or death (P=.047). The life-table analysis showed that the group 1 patients had a much greater risk of dying suddenly (P=.05). CONCLUSIONS: Right bundle-branch block and precordial injury pattern in V1 through V3 is common in SUDS patients and represents an arrhythmogenic marker that identifies patients who face an inordinate risk of ventricular fibrillation or sudden death.

Presence of immunoglobulins, C3 and cytolytic C5b-9 complement components on the surface of erythrocytes from patients with beta-thalassaemia/HbE disease.

The occurrence of IgG, IgM, IgA, C3 and C5b-9 complement complexes on erythrocytes from 43 patients with beta-thalassaemia HbE disease was investigated. Indirect immunoradiometric assays using radioiodinated protein A were employed to quantify the individual components. We confirmed that circulating erythrocytes from thalassaemic patients contained elevated amounts of IgG, and small but significant amounts of C3. In addition, small but significant amounts of C5b-9 were detected. Levels of cell-bound IgG, C3 and C5b-9 were higher in splenectomized versus non-splenectomized patients. The presence of C5b-9 on circulating cells from five splenectomized patients was confirmed by an ELISA employing a monoclonal antibody specific for a C5b-9 neoantigen. When C5b-9 positive cells from two patients were solubilized with detergent and subjected to sucrose density gradient centrifugation, the terminal complexes sedimented as 25-40S macromolecules, thus behaving as membrane C5b-9 complexes. The presence of C8 and C9 in these high molecular weight fractions was directly demonstrated by Western blotting. These results constitute the first demonstration that circulating diseased erythrocytes may carry low numbers of potentially cytolytic C5b-9 complement complexes which may be partly responsible for the known ionic disturbances found in thalassaemic cells. Both bound C3 and C5b-9 could promote removal of diseased cells in the reticuloendothelial system.

Rapid detection and identification of dengue viruses by polymerase chain reaction (PCR).

A polymerase chain reaction (PCR) method using sets of newly designed primers for rapid detection and simultaneous identification of dengue virus serotypes was developed and tested. The test is based on two sets of primers specific within the envelope (E) and non-structural (NS1) regions of the dengue-virus genome. Two sets of universal primers that bind to two target sequences which are shared by all the four serotypes of the virus within the E and NS1 regions are used. The resulting products are further amplified by another pair of inner or nested universal primers, which also bind to another set of shared sequences within the E and NS1 regions, respectively. The nested PCR of both the E and NS1 regions can detect dengue virus of all the four serotypes at a sensitivity of 1 plaque forming unit (pfu) or less. For the identification of serotypes, a mixture of four pairs of serotype-specific primers, specific to the E region, was used. The primers have been designed to bind to serotype specific sequences within the regions flanked by the outer universal primers, and giving the amplified products of different sizes, each corresponds to one particular serotype (405 bp for Den1, 346 bp for Den2, 196 bp for Den3, and 143 bp for Den4). A protocol has been developed and successfully applied to detect dengue virus in cell-culture supernatants and patients sera. The technique is simple and rapid, capable of not only detecting the dengue virus but also identifying the serotypes of the virus in clinical specimens.

The spectrum of endemic renal tubular acidosis in the northeast of Thailand.

We have previously reported a high prevalence of endemic renal tubular acidosis (EnRTA) in the northeast of Thailand, and our subsequent studies provided evidence that K deficiency exists in the same region. Since tubulointerstitial damage is associated with K deficiency, we postulate that this might be implicated in the pathogenesis of EnRTA and, if so, that a spectrum of tubulointerstitial abnormalities can be anticipated. In this study we evaluated renal acidification ability in 4 patients and in 11 of their relatives. We used a 3-day acid load (NH4Cl 0.1 g/kg/day) followed by 20 mg oral furosemide and monitored the maximal renal concentrating ability using water deprivation and intranasal 1-deamino-D-arginine vasopressin. The results showed that the subjects could be divided into three groups; normal relatives of the patients, those with suspected renal tubular acidosis, and patients with overt EnRTA who had chronic metabolic acidosis and a low rate of excretion of NH4+. The rate of excretion of K was very low (20 +/- 4 mmol/day) in patients with EnRTA and in their relatives with suspected EnRTA. The transtubular K concentration gradient was also very low in their relatives, especially in patients with suspected EnRTA (2.8 +/- 0.2). With a 3-day NH4Cl load, the rate of excretion of NH4+ was very low in patients with EnRTA (32 +/- 9 mmol/day), and the relatives with suspected EnRTA also had a decreased capacity to excrete NH+4 (50 +/- 14 mmol/day). In contrast, the normal relatives excreted 92 +/- 12 mmol of NH+4/day. The patients with EnRTA could lower their urine pH to less than 5.5 after the acid loading (6.2 +/- 0.3). After furosemide (20 mg), the NH4+ excretion in the patients with EnRTA was lower than in the normal relatives. Moreover, the minimum urine pH in patients with EnRTA did not fall (6.1 +/- 0.2), but there was a fall to 4.8 +/- 0.1 in the patients with suspected EnRTA after furosemide treatment. In conclusion, there was a spectrum of tubulointerstitial abnormalities ranging from suspected to overt distal RTA in a geographic area known to have a high prevalence of K deficiency. K deficiency might be the important pathogenetic factor of EnRTA in the northeast of Thailand.

Prevalence of endemic distal renal tubular acidosis and renal stone in the northeast of Thailand.

We have previously reported a large group of patients with endemic distal renal tubular acidosis (EdRTA) admitted to the hospitals in the northeast of Thailand. Since large number of patients were identified in a relatively short period of time, and in an area whose population is homogeneous, we were led to investigate the prevalence of the condition in the area. A survey was conducted in five villages (total population of 3,606) within the northeast of Thailand. 3,013 villagers were examined for urinary citrate concentration and short acid loading test was performed in those with low urinary citrate. 2.8% of the population (2.2-3.4%, 95% confidence interval) failed to lower their urine pH after acid loading; within this group, 0.8% of the population had serum potassium less than or equal to 3.5 mEq/l. In addition a large number of villagers were found to have low urinary citrate concentration and there was concurrent high prevalence of renal stone. The prevalence of EdRTA and renal stone was higher in villagers with poorer socioeconomic status, suggesting that environmental factors play a major role in their pathogenesis. Villagers with acidification defect have 2.4 times the chance of having renal stone and/or nephrocalcinosis. EdRTA is therefore one of the important factors responsible for the high prevalence of renal stone in the area. In conclusion we have confirmed the high prevalence of EdRTA in the northeast of Thailand and provided data showing high prevalence of renal stone and hypocitraturia in the same population.

Anti-dengue IgG detection by an indirect ELISA.

Protein-free culture media were originally developed for hybridomas to simplify downstream processing and purification. For the same reasons, we have used these protein-free media for passaging dengue 2 virus in C6/36 cells. This provided us with an infected supernatant (DenPF) which could then be used as coating antigens for an indirect enzyme-linked immunosorbent assay (ELISA) to determine dengue IgG levels. Using this preparation, the main immunogenic band as seen by immunoblot appeared to be viral envelope protein (E). Without the high concentrations of "competing" proteins from fetal calf serum (FCS), the Den2PF could be directly coated onto 96-well ELISA plates. The amount of viral proteins in Den2PF appeared to be sufficient so that there was no need for further purification steps, eg polyethylene glycol (PEG) precipitation, which made this preparation cost effective. It compared favorably with the dengue dot enzyme immunoassay (DEIA; sensitivity of 95.7% and specificity of 95.2%).

Lupus nephritis in Thailand: clinicopathologic findings and outcome in 569 patients.

The prognosis of lupus nephritis patients in Thailand has been reported to be poorer than that in Western countries since 1978. After a great evolution in management, we re-evaluate the long-term outcome in patients who were treated and followed up at Siriraj Hospital in Bangkok from 1984 to 1991. Clinical and pathologic records were collected from 569 patients (515 females and 54 men) who were followed up for a mean period of 38.7 +/- 34.6 months. The mean age was 28 +/- 10 years and the median duration of symptoms prior to admission was 7 months. Hypertension was diagnosed in 32.4% of patients and 41.3% had serum creatinine greater than 1.5 mg/dL. Nephrotic-range proteinuria was found in 43.6% of patients and creatinine clearance less than 50 mL/min was found in 58.0%. Of the 314 patients who underwent renal biopsy, the most common histologic finding was diffuse proliferative glomerulonephritis (61.5%). The overall probability of survival was 76.5% at 60 and 90 months after diagnosis. Initial presence of hypertension, renal insufficiency (creatinine clearance < 25 mL/min), and World Health Organization histology class IV and III in the biopsied patients were the three independent factors significantly associated with lower survival probability. Neither gender nor amount of proteinuria was the predictive factor for poor outcome. During the follow-up period, 89 patients died and two patients entered a chronic dialysis program. The two leading causes of death were infection (50.5%) and uremia (28.6%).(ABSTRACT TRUNCATED AT 250 WORDS)

Glomerulonephritis in beta-thalassemia Hb-E disease: clinical manifestations, histopathologic studies and outcome.

We presented 8 patients with beta-thal/Hb E with glomerular diseases. Diverse glomerular lesions were seen, but diffuse endocapillary glomerulonephritis was the most common. The clinical manifestations of acute glomerulonephritis in beta-thal/Hb E differed from typical cases in the older age group, female preponderance, longer duration of edema, less hypertension, marked proteinuria, hypoalbuminemia and hypertriglyceridemia and also a longer period of recovery but their outcome was still favorable despite many risk factors of renal injury. Renal biopsy was necessary in doubtful cases to detect the correct diagnosis and give proper management. The association and mechanism of glomerulonephritis in these patients require further prospective study.

Lupus nephritis in males: 8-year experience at Siriraj Hospital.

During 1984 to 1991, 54 out of 569 lupus nephritis patients at Siriraj Hospital were male (F:M sex ratio = 10:1). Mean age of the males was 29.8 +/- 14.6 years, range 12 to 69. The three most common extrarenal manifestations were anemia, cutaneous, and musculoskeletal involvement (74.5, 51.1, and 43.9%, respectively). The major renal manifestations were edema (75.9%) with heavy proteinuria over 3.5 g/day in 62.2% and nephrotic/nephritic findings in 51.9% of cases. Hypertension was found in 35.2%. Mean serum creatinine was 2.0 +/- 1.4 mg/dl while 60.5% of cases had creatinine clearance below 50 ml/minute. Mean serum albumin was 2.6 +/- 0.8 g/dl, cholesterol 262.8 +/- 129.5 and triglycerides 343.2 +/- 244.6 mg/dl. Interestingly, hypercholesterolemia (> 250 mg/dl) was found only in 44.8% of cases with nephrotic syndrome. Antinuclear antibody was demonstrated in 91.5%, anti-dDNA antibody in 64.4% and LE cells in 40.4% of cases. Renal biopsy was done in 45 patients and 30 cases (66.7%) were classified as diffuse proliferative nephritis (WHO type IV), 15.6% of type II, 6.7% each of type III and V, with the rest of type V plus IV (4.4%). Tubulointerstitial inflammation was found in 77.3% of cases. During the follow-up period (42 +/- 35.8 months), 6 patients died. The cause of death were uremia in 3, infection in 2, and cardiac failure in 1. By life-table analysis, the probabilities of survival for 1 and 5 years were 89.5 and 80.6%, respectively. In comparison between sexes, except for a higher amount of urinary protein excretion (4.5 +/- 3.1 vs 3.5 +/- 3.0 g/day, p < 0.05), there were no statistically significant differences in clinical and pathological parameters, and probability of survival.

Pathogenesis of sudden unexplained nocturnal death (lai tai) and endemic distal renal tubular acidosis.

Sudden unexplained nocturnal death (SUND), a disorder of unknown cause that occurs in otherwise healthy young adults, mostly male, during their sleep, is prevalent in the north-east region of Thailand, where it has been known for generations as lai tai. It occurs in the same population and area where hypokalaemic periodic paralysis (HPP), endemic distal renal tubular acidosis (EdRTA), and renal stones are also endemic. SUND has occurred in families of patients with EdRTA, and HPP can present as sudden onset of muscle parlysis with potentially lethal cardiac arrhythmias and respiratory failure from severe hypokalaemia occurring in the middle of the night. Surveys in which serum and urinary potassium have been measured indicate a deficiency of the electrolyte in the population. Potassium deficiency is probably the prime factor responsible for SUND and HPP. Low urinary citrate concentrations and the high prevalence of acidification defects in the population indicate that potassium deficiency is also responsible for the prevalence of EdRTA and for renal stones.

Analysis of serum urinary proteins in normal and renal diseases by cellulose acetate electrophoresis.

A method using dried polyacrylamide gel to concentrate urine samples has been described, tested and used for the purpose of urine protein analysis. Concentrated urine samples from 10 normals and 100 patients with IgM nephropathy and systemic lupus erythematosus (SLE) were analysed by cellulose acetate electrophoresis (CAE). The results demonstrated that the patterns of proteins in the electrophoresis could be used to discriminate the two diseases. The best discriminating power was found in the logarithm of gamma globulin to albumin ratio. In IgM nephropathy the ratio of gamma globulin to albumin is much smaller than the ratio in SLE, indicating that relatively larger gamma globulins were excreted in SLE. In addition, the ratio can be used to discriminate subgroups of patients with IgM nephropathy. Urine from patients with IgM nephropathy with focal and segmental changes showed a significantly higher ratio. The study indicated the usefulness of the technique in discriminating the two common glomerular diseases.

Urinary constituents in an endemic area of stones and renal tubular acidosis in northeastern Thailand.

Nephrolithiasis and endemic renal distal tubular acidosis are common in northeastern Thailand. The etiology is still unknown. It is generally accepted that urine electrolytes influence the capacity of urine to inhibit or promote renal and also bladder stones. The purpose of this study was to analyse the composition of the urine in the indigenous population in the northeast area and compare their values with data obtained from a group of age matched adults, living in Bangkok. Twenty-four hour urine samples from 23 normal adult villagers from six villages within the province of Khon Kaen and 34 normal adults living in Bangkok were collected, and the daily excretion of creatinine, uric acid, calcium and inorganic phosphate, sodium, potassium, chloride, magnesium and oxalate were assayed. Daily urinary sodium, potassium, chloride and phosphate of the villagers were significantly lower than those of Bangkokians. No difference in the urinary excretion of calcium, magnesium, uric acid, oxalate and creatinine was found. The Na/Ca, and Ca/PO4 ratios of villagers were significantly lower than those of the Bangkok subjects. The villagers excreted significantly lower amounts of Na in the face of relatively higher urinary Ca. The above data, combined with our previous study showing the low values of urinary citrate in the villagers in the same areas, strongly indicate that the indigeneous population is at high risk in developing urolithiasis. The causes for these electrolyte abnormalities are still unknown. Low contents of the major electrolytes in their diets might play an important role. Low phosphate output indicates low protein diets.(ABSTRACT TRUNCATED AT 250 WORDS)