Urinary oxalate and glycolate excretion in healthy infants and children

The molar ratios of oxalate and glycolate over creatinine were determined in single urine samples of 26 infants and 27 children aged 1–5 years. In 135 children aged 5–16 years, two urine specimens were collected, one before breakfast and one at noon. Oxalate was determined by oxalate oxidase, and glycolate was measured by a colorimetric method (improved chromatotropic acid-sulphuric acid assay after prior purification by cation and anion exchanger). Both ratios (expressed in mmol/mol creatinine and analysed on a log-normal basis) were highest in infants 0–6 months old [mean oxalate 147 (95% confidence interval: 60–360), mean glycolate 175 (72–425)]. The mean oxalate ratio was 72 mmol/mol (29–174) at the age of 7–24 months, 44 (19–101) at the age of 2–5 years and 22 (12–40) in adolescents aged 16 years. Molar glycolate ratios were higher, but disclosed the same pattern. Oxalate and glycolate ratios in fasting urines did not differ significantly from those in noon samples (except glycolate in the oldest age group). Oxalate ratios correlated well with glycolate ratios in children up to 5 years of age only. Random urine samples are thus suitable for screening. However, interpretation of data requires use of age-specific reference values that are based on comparable methods.     

Recurrence of nephrocalcinosis after renal transplantation in an adult patient with primary hyperoxaluria type I

The medical history of a 42-year-old patient with primary hyperoxaluria type I is presented. Primary hyperoxaluria was suspected after renal transplantation, when oxalate deposits were found in a biopsy of the kidney graft. Diagnosis of type I hyperoxaluria was confirmed by the finding that significantly increased amounts of glycolic acid and oxalic acid were excreted. Treatment of the patient with 500 mg pyridoxine daily resulted in a decrease of the excretion of oxalate to normal values.     

线粒体途径在高草酸尿大鼠肾小管上皮细胞凋亡中的作用

目的探讨线粒体途径在高草酸尿大鼠肾小管上皮细胞凋亡中的作用。方法雄性成年SD大鼠24只,随机分为4组,每组6只,设为正常组、高草酸尿组、环孢素A（CsA）对照组、CsA干预组。各组均在第4周末处死并取左肾,常规HE染色检测肾小管草酸盐结晶沉着情况;原位末端标记法（TUNEL）检测肾小管上皮细胞凋亡程度;免疫组化检测细胞色素c（CytoC）、Caspase-3和Caspase-9蛋白表达。结果高草酸尿组和CsA干预组肾小管腔内可见明显晶体沉着,正常组和环孢素对照组未见晶体沉着;与其它3组比较,高草酸尿组凋亡指数显著增高、CytoC、Caspase-3和Caspase-9表达明显增强（P〈0.01）。结论线粒体途径参与了高草酸尿大鼠肾小管上皮细胞凋亡,CsA具有降低凋亡指数及抑制CytoC、Caspase-3和caspase-9蛋白表达的作用。     

Atypical presentation of distal renal tubular acidosis in two siblings

Primary distal renal tubular acidosis (dRTA) is an inherited disease characterized by the inability of the distal tubule to lower urine pH <5.50 during systemic acidosis. We report two male siblings who presented with severe hyperchloremic metabolic acidosis, high urinary pH, nephrocalcinosis, growth retardation, sensorineural hearing loss, and hypokalemic paralysis. Laboratory investigations revealed proximal tubular dysfunction (low molecular weight proteinuria, generalized hyperaminoaciduria, hypophosphatemia with hyperphosphaturia, and hypouricemia with hyperuricosuria). There was significant hyperoxaluria and laboratory evidence for mild rhabdomyolysis. Under potassium and alkali therapy, proximal tubular abnormalities, muscular enzymes, and oxaluria normalized. A homozygous mutation in the ATP6V1B1 gene, which is responsible for dRTA with early hearing loss, was detected in both siblings. In conclusion, proximal tubular dysfunction and hyperoxaluria may be found in children with dRTA and are reversible under appropriate therapy.     

Pyridoxamine lowers oxalate excretion and kidney crystals in experimental hyperoxaluria: a potential therapy for primary hyperoxaluria

In order to prevent kidney stones and nephrolithiasis in hyperoxaluria, a new treatment that specifically reduces oxalate production and therefore urinary oxalate excretion would be extremely valuable. Pyridoxamine(PM) could react with the carbonyl intermediates of oxalate biosynthesis, glycolaldehyde and glyoxylate, and prevent their metabolism to oxalate. In PM treated rats, endogenous urinary oxalate levels were consistently lower and became statistically different from controls after 12 days of experiment. In ethylene glycol-induced hyperoxaluria, PM treatment resulted in significantly lower (by ~50%) levels of urinary glycolate and oxalate excretion compared to untreated hyperoxaluric animals, as well as in a significant reduction in calcium oxalate crystal formation in papillary and medullary areas of the kidney. These results, coupled with favorable toxicity profiles of PM in humans, show promise for the therapeutic use of PM in primary hyperoxaluria and other kidney stone diseases.     

Hypocitraturia as a risk factor for nephrocalcinosis after kidney transplantation

Calcium-oxalate crystal deposition in kidney transplant biopsy specimen led us to investigate the impact of calcineurin inhibitor treatment on urinary excretion of lithogenic and stone inhibitory substances in 53 children after successful kidney transplantation (KTx) receiving cyclosporine A (CsA) or tacrolimus. We compared the values obtained with those of 12 patients with recurrent nephrotic syndrome under CsA and of 6 patients with Rasmussen encephalitis (RE) under tacrolimus therapy. Renal ultrasound examinations were repeatedly performed. Hypocitraturia was found in 69% of patients, with KTx patients having a significantly lower urinary citrate excretion than those receiving calcineurin inhibitors for other reasons. Secondly, we found hyperoxaluria in 35% of patients, again especially in those after KTx. No significant difference in urinary substances was seen comparing CsA with tacrolimus treatment. Urolithiasis was found in one and calcium-oxalate crystal deposition in biopsy specimen of three KTx patients. Calcineurin inhibitor treatment can lead to significant hypocitraturia, especially in patients after KTx receiving the highest dose of medication. Hyperoxaluria is primarily the result of a removal of significant body oxalate stores, deposited during dialysis, but may not be suspected as a specific side effect of calcineurin inhibitor therapy. Both findings can increase the risk for urolithiasis or nephrocalcinosis.     

Vitamin B6 metabolites in idiopathic calcium stone formers: no evidence for a link to hyperoxaluria

Vitamin B6 metabolites and their potential correlates to urinary oxalate excretion in idiopathic calcium stone formers (ICSF) compared with healthy subjects were investigated. This clinical study was performed in a population of male ICSF with (Hyperoxalurics, n=55) or without hyperoxaluria (Normooxalurics, n=57) as well as in 100 healthy male control subjects. Pyridoxal 5-phosphate serum concentration (S-pyridoxal 5P) and 24-h urinary excretion of 4-pyridoxic acid (U-4pyridoxic acid) were measured using HPLC; 24-h urinary excretion of oxalate (U-oxalate) was measured concurrently. A subgroup of subjects (40 Hyperoxalurics, 15 Normooxalurics and 50 controls) underwent the same measurements before and after 7-day pyridoxine loading per os (pyridoxine hydrochloride, 300 mg/d). Under usual conditions, U-4pyridoxic acid was similar in the three groups, whereas mean S-pyridoxal 5P was significantly lower (p<0.0001) in the Hyperoxalurics (59.6±21.2 nmol/L) and in the Normooxalurics (64.9±19.7 nmol/L) than in the controls (86.0±31.0 nmol/L). No correlation could be found between U-oxalate and U-4pyridoxic acid or S-pyridoxal 5P. After B6 loading, S-pyridoxal 5P was still significantly lower in the Hyperoxalurics (415±180 nmol/L, p<0.001) and in the Normooxalurics (429±115 nmol/L, p=0.036) than in the controls (546±180 nmol/L), although there was no difference between groups for U-4pyridoxic acid. No correlation in any group could be found between changes in U-oxalate and changes in U-4pyridoxic acid or S-pyridoxal 5P. Although there is no vitamin B6 deficiency in ICSF with or without hyperoxaluria, these patients, on average, have lower levels of S-pyridoxal 5P than healthy subjects. However, this slight decrease does not seem to account for idiopathic hyperoxaluria.     

The etiology of urolithiasis in udaipur (Western Part of India)

Summary Fifty-two cases of urinary tract calculus disease were investigated for dietary habits, routine chemical and microscopic urinalysis, bacterial culture, quantitative analysis of 24 h urine sample and qualitative analysis of the stones. 54 out of the 56 stones analysed were of mixed type. Magnesium ammonium phosphate was present in 78.2% stones. Dietary habits revealed principal dependence on cereals, lack of animal proteins, consumption of oxalate rich vegetables and widespread consumption of tea. Urinary tract infection was present in 63.7% of the cases. Significant calcium oxalate crystalluria (2+ to 4+) was present in 34.6% of the cases. Hyperoxaluria, hypercalciuria associated with hyperoxaluria-lower excretion of magnesium and citric acid were important urinary risk factors in the local population. These observations strongly suggest the multifactorial etiology of stone disease in this region. Imbalanced nutrition and urinary tract infection were the principal risk factors for urolithiasis in this study.This paper was presented by Dr. A. K. Pendse at the 24th Biennial Congress of the International College of Surgeons at Manila (Philippines)     

夹竹桃麻素对高草酸尿症大鼠肾脏氧化应激损伤的保护作用

目的 观察NADPH氧化酶特异抑制剂夹竹桃麻素（apocynin）对高草酸尿症大鼠肾脏氧化应激（OS）损伤的保护作用。 方法 自由饮用含有0.8%乙二醇的水4周建立高草酸尿症SD大鼠模型。大鼠按随机数字表法分为4个组：空白组、高草酸尿症组、apocynin干预组、apocynin对照组。后两组给予apocynin（0.2 g&#8226;kg-1&#8226;d-1）灌胃,对照组给予正常饮水。4周后检测大鼠肾脏OS 指标（尿H2O2和8-异前列腺素）,以及Ccr及肾脏/体质量比值。免疫组化观察NADPH氧化酶亚基p47phox在肾脏中的表达位置。RT-PCR和免疫印迹法分别检测肾组织NADPH氧化酶亚基p47phox、gp91phox、Nox-1 mRNA以及p47phox蛋白的表达水平。 结果 p47phox在各组肾脏中均有广泛的表达,包括肾皮质区、内髓区、外髓区等。与空白组比较,高草酸尿症组大鼠尿H2O2和8-异前列腺素水平显著升高,Ccr降低,肾脏/体质量比值增高（均P < 0.05）;肾脏p47phox、gp91phox和Nox-1 的mRNA表达均显著增加（均P ＜ 0.05）, p47phox蛋白表达也增多（P ＜ 0.01）。apocynin干预治疗可抑制肾脏p47phox、Nox-1 mRNA及p47phox蛋白的表达,但gp91phox mRNA表达未明显减少,而大鼠尿H2O2和8-异前列腺素水平下降,Ccr增加,肾脏/体质量比值减少,但仍高于对照组水平。 结论 NADPH氧化酶是高草酸尿症诱导大鼠肾脏OS损伤过程中活性氧形成的来源之一。使用apocynin抑制NADPH氧化酶活性可部分减轻肾脏的OS损伤程度,保护肾功能。     

血管紧张素Ⅱ刺激高草酸尿症大鼠肾脏NADPH氧化酶的表达

目的： 观察肾素-血管紧张素系统（RAS）和NADPH氧化酶在高草酸尿症大鼠肾脏氧化应激（OS）形成中的相互作用。方法: 采用0.8%乙二醇饮水法诱导建立高草酸尿症大鼠模型。动物分6个组（n=8）,A组:空白组;B组：高草酸尿症组;C组：高草酸尿症+apocynin治疗组;D组：单纯apocynin治疗组;E组：高草酸尿症+losartan治疗组;F组：单纯losartan治疗组。后4组分别灌胃给予apocynin（0.2 g·kg-1·d-1）或losartan（30 mg·kg-1·d-1）。4周后检测大鼠尿液、肾组织中的OS指标（尿8-IP和肾组织SOD活性）,放免法检测肾组织血管紧张素Ⅱ（AngⅡ）的含量,免疫组化法观察NADPH氧化酶亚单位P47phox蛋白在肾脏中的表达位置,RT-PCR法检测肾组织p47phox mRNA的表达水平。结果: p47phox在各组大鼠肾脏中都有广泛表达,表达部位包括肾皮质、内髓、外髓。与A组比较,B组尿液8-IP明显增多,肾组织SOD活性降低,肾组织AngⅡ含量增多,p47phox mRNA在肾组织中的表达水平也明显增多。使用apocynin（C组）和losartan（E组）均可抑制肾组织p47phox mRNA的表达,同时肾脏的OS程度减轻。结论: 在高草酸尿症大鼠模型中,肾脏p47phox mRNA表达增多,导致肾脏OS;同时肾脏RAS也被激活,后者可通过刺激p47phox mRNA的表达而促进肾脏OS程度增加。