Urinary Lactic Dehydrogenase Isoenzyme Analysis in Children with Spinal Lesions

ABSTRACT. In 48 children with spinal lesions and micturition problems urinary lactic dehydrogenase (LDH) isoenzymes were analyzed. They had higher total LDH activities (716.8 ± 1050.2 nkat/1), isoenzymes V percents (22.2 ± 13.0 %) and isoenzyme V activities (203.4 ± 308.4 nkat/l) than those of healthy children (150.0 ± 83.4 nkat/1,1.9 ± 1.0 %, 5.0 ± 3.3 nkat/1). Many subjects had an isoenzyme V-dominant LDH isoenzyme pattern. Among 48 subjects the patients with pyuria, bacteriuria or abnormal pyelograms had markedly high total LDH activities, isoenzyme V percents and isoenzyme V activities. The rise in LDH isoenzyme V levels may reflect the renal damage in the patients with neurogenic bladders.     

Abnormal lactic dehydrogenase isoenzymes in patients of Indian childhood cirrhosis and their siblings

In fifteen patients with Indian childhood cirrhosis (I.C.C.) total lactic dehydrogenase (LDH) activity was increased as compared with controls (P<0.001). The isoenzyme pattern in I.C.C. patients was quite distinctive from that observed in normal controls and in patients with acute viral hepatitis. In I.C.C. there was a two fold increase in LDH isoenzyme-1, and a decrease in LDH-2 and LDH-4. Sixty per cent patients with I.C.C. had abnormal bands between LDH-1 and 2 and LDH-2 and 3. Siblings of the patients with I.C.C. had normal total LDH activity, and showed double ringed bands in the region of LDH 1–3. The abnormal bands in patients of I.C.C. are explained on the basis of hybridization of LDH with other serum components.     

Changes in Lactate Dehydrogenase Isoenzymes Associated with Relapse of Childhood Acute Lymphocytic Leukemia

Twenty-eight children with high-risk acute lymphocytic leukemia underwent monthly serum lactate dehydrogenase (LDH) and WH isoenzyme fraction determinations to examine whether WH isoenzpe fractions change with an increase in the body burden of tumor cells. The 9 patients who relapsed and 5 patients who presented with leukemia during the study period had a slightly lower mean LDH-1 isoenzyme fraction. When the period from 3 months before to 3 months after relapse was examined, significant increases in the LDH-3 isoenzyme fraction and decreases in the LDH-1 and LDH-2 isoenzyme fractions were seen at the time of relapse. These results were highly significant when patients with non-T-cell and T-cell leukemia were combined and when bone marrow and central nervous system relapse was included. The changes at relapse appeared to revert with intensification of chemotherapy. The changes at relapse were not different in magnitude from random variation occurring in patients who remained in remission throughout the study. Although changes in LDH isoenzymes appeared to occur at the time of relapse compared with the periods immediately before and after relapse, these changes were not specific for relapse. LDH isoenzymes do not appear to be useful in predicting relapse in children with leukemia.     

Changes in serum lactate dehydrogenase activity in children with atopic dermatitis

Background: In recent years an increase has been seen in the number of patients with severe atopic dermatitis (AD) accompanied with generalized typical eruptions. Some markers indicating the severity of the disease and symptom changes are very useful, and therefore the purpose of the present study was to investigate serum lactate dehydrogenase (LDH) as such a marker. Methods: A total of 58 children with AD were enrolled. The severity of the disease was graded on the basis of the extent of eruptions and the severity of atopic symptoms. The fraction of serum LDH, number of eosinocytes in the peripheral blood, and serum IgE levels were also determined. Results and Conclusion: There was a close correlation between the severity of cutaneous symptoms and serum LDH activity, and between severity and eosinocyte count, but no relationship was seen between serum IgE levels and severity of the disease. The aforementioned factors were determined in a time‐related way. As the patients' condition improved, serum LDH activity tended to decline, but there were no consistent changes in eosinocyte count in the peripheral blood or serum IgE level. On LDH isozyme the levels of LDH4 and LDH5 were high. Tissue showed high LDH activity, especially in epidermides. These results suggest that serum LDH activity is a useful marker.     

乳酸脱氢酶在儿童难治性肺炎支原体肺炎诊断和治疗中的意义

目的 探讨乳酸脱氢酶(lactic dehydrogenase,LDH)在儿童难治性肺炎支原体肺炎(refractory Mycoplasma pneumoniae pneumonia,RMPP)诊断和治疗中的意义.方法 对2013年6月至2016年6月南方医科大学附属深圳妇幼保健院儿科收治的肺炎支原体肺炎(Mycoplasma pneumoniae pneumonia,MPP)患儿,均给予红霉素治疗.根据RMPP的定义,将其分为普通MPP组和RMPP组.RMPP组采用红霉素基础上添加甲泼尼龙治疗.根据疗效,将RMPP患儿分为有效组和无效组.所有患儿均检测血LDH、WBC计数、C-反应蛋白、红细胞沉降率(erythrocyte sedimentation rate,ESR)、丙氨酸氨基转移酶(ALT)、天门冬氨酸氨基转移酶(AST)及肌酸激酶(CK).分别比较RMPP组和普通MPP组、有效组和无效组之间在治疗前后上述指标有无差异.结果 共纳入253例受试者,其中普通MPP组161例,RMPP组92例.与普通MPP组相比,RMPP组患儿年龄更大,LDH、ESR、ALT、AST水平更高(P＜0.05).Logistic回归分析显示,LDH(OR=1.029,95%CI 1.020~1.037)、ESR(OR=1.063,95%CI 1.009~1.120)为RMPP的预测因素(P＜0.05).受试者工作特征曲线表明,LDH临界值为400.50U/L时,曲线下面积最大为0.959,95%CI 0.936~0.983.RMPP组添加甲泼尼龙治疗后,患儿临床症状迅速改善,有效组LDH、ESR水平显著降低(P＜0.05).结论 血清LDH可能为早期识别RMPP和判断疗效的一个重要指标.     

地中海贫血患儿血清乳酸脱氢酶活性分析及临床意义

目的探讨血清乳酸脱氢酶(LDH)在地中海贫血患儿中的变化及临床意义。方法对近年住我院的地中海贫血患儿的血清乳酸脱氢酶进行检测,并与急性溶血组与非溶血组比较。结果地中海贫血组LDH活性较非溶血组明显升高(P<0.01)。地贫合并感染时LDH明显升高,与地贫非感染状态下比较有差异性(P<0.01),与急性溶血组比较无差异性(P>0.05)。地贫组中,Hb<60 g/L时LDH活性较Hb>60 g/L时明显升高(P<0.05)。结论地中海贫血患者血清乳酸脱氢酶活性升高,合并感染时升高明显,与溶血程度呈正相关,可作为病情观察的重要指标。     

Urinary lactic dehydrogenase isoenzyme analysis in children with spinal lesions

In 48 children with spinal lesions and micturition problems urinary lactic dehydrogenase (LDH) isoenzymes were analyzed. They had higher total LDH activities (716.8 +/- 1,050.2 nkat/I), isoenzymes V percents (22.2 +/- 13.0%) and isoenzyme V activities (203.4 +/- 308.4 nkat/I) than those of healthy children (150.0 +/- 83.4 nkat/I, 1.9 +/- 1.0%, 5.0 +/- 3.3 nkat/I). Many subjects had an isoenzyme V-dominant LDH isoenzyme pattern. Among 48 subjects the patients with pyuria, bacteriuria or abnormal pyelograms had markedly high total LDH activities, isoenzyme V percents and isoenzyme V activities. The rise in LDH isoenzyme V levels may reflect the renal damage in the patients with neurogenic bladders.     

血清神经元特异性烯醇化酶和乳酸脱氢酶检测在小儿Ⅳ期神经母细胞瘤诊治中的应用

目的探讨血清神经元特异性烯醇化酶(NSE)和乳酸脱氢酶(LDH)水平在Ⅳ期神经母细胞瘤患儿治疗前及自体外周血造血干细胞移植(APBSCT)治疗前后的变化及其临床意义。方法选择2006年10月-2008年8月我科收治的18例Ⅳ期神经母细胞瘤患儿,对治疗前、APBSCT治疗前后血清NSE与LDH水平进行比较,分析血清NSE、LDH水平与病情变化的关系,探讨血清NSE与LDH水平的相关性。结果 (1)Ⅳ期神经母细胞瘤患儿治疗前血清NSE阳性率高(16/18例),NSE、LDH水平均明显高于治疗有效时(P<0.01);(2)经过化疗、手术切除及放疗等综合治疗,完全缓解期患儿血清NSE、LDH水平与部分缓解期患儿相比差异均有显著性(P<0.05);(3)肿瘤进展期患儿血清NSE、LDH水平与治疗前相比差异无显著性(P>0.05);(4)APBSCT治疗结束后1个月NSE、LDH水平,移植前完全缓解期8例移植后仍为完全缓解,与移植前相比NSE水平无明显变化(P>0.05),但LDH水平显著下降(P<0.05);移植前处于部分缓解期的6例中,3例移植后获得完全缓解,3例获得部分缓解,与移植前相比,NSE、LDH水平均有所下降(P<0.05);移植前处于进展期的4例中,1例死亡未测,3例造血重建后病情稍缓解,NSE、LDH水平与移植前相比差异无显著性(P>0.05)。NSE与LDH水平在疾病病程中呈正相关(r=0.55,P<0.01)。结论血清NSE、LDH水平可反映Ⅳ期神经母细胞瘤患儿肿瘤负荷,与肿瘤疗效和复发有关,提示其可作为监测神经母细胞瘤疗效的辅助性指标。     

Serum alkaline phosphatase isoenzymes in epileptic children receiving anticonvulsant drugs

In 40 epileptic children on long-term anticonvulsant treatment, serum alkaline phosphatase (AP) isoenzymes were separated semiquantitatively using a combination of L-phenylalanine inhibition and heat inactivation. Though mean total serum AP activity was significantly increased compared to age matched controls, only 4 individual values exceeded the upper limit (mean + 2SD) of the reference sample. In epileptics the mean activity of the heat-sensitive non L-phenylalanine sensitive AP fraction (non-LPSAP) was significantly increased (P<0.01) and the mean Q-value (i.e. percentage ratio of heat-stable non-LPSAP/non-LPSAP) was significantly decreased (P<0.05), thus indicating an enhancement of the bone isoenzyme during anticonvulsant treatment. In 4 patients the isoenzyme pattern was abnormal although total serum AP activity was normal and in 3 of them the deviation indicated enhanced bone isoenzyme. The data provide evidence that in anticonvulsant treated children the bone isoenzyme, rather than hepatobiliary isoenzyme fraction, may be increased even when total serum AP activity is normal. Thus, semiquantitative separation of serum AP isoenzymes may be a helpful guide as to whether or not an epileptic child should be given vitamin D.Supported in part by Deutsche Forschungsgemeinschaft (Ba 246/11)The data form part of the thesis of H. Günther, Medical School of Lübeck     

Urinary lactic acid dehydrogenase activity and the site of urinary tract infections

A report that elevated urinary lactic acid dehydrogenase (LDH) isoenzyme 5 activity is a reliable tool for separating patients with upper from those with lower urinary tract infections (UTIs) led us to study urinary LDH enzyme activity in girls having bladder washout studies to localize the site of infection. Urinary LDH isoenzyme 5 activity in 64 instances of lower UTI was 16.1 +/- 3.3%, a value not significantly different than that of 18.2 +/- 12.6% found in 26 instances of upper tract infection (t = 0.8726, P = 0.1928). The data show that LDH isoenzyme 5 activity is of no value for localization of the site of a UTI. The data of these studies also showed that urinary LDH enzyme activity clearly separates girls with UTIs from those without infections, but it is unlikely that this finding will be of value in diagnosis or management.     

Lactic dehydrogenase isoenzymes in cerebrospinal fluid of children with Guillain-Barré syndrome.

BACKGROUND: Increased levels of lactic dehydrogenase (LDH) in the cerebrospinal fluid (CSF) have been reported in association with several intracranial pathologies. No studies have been performed on patients with Guillain-Barré syndrome (GBS). AIMS: To study LDH isoenzymes in CSF of children with GBS. METHODS: CSF samples collected from nine patients with GBS were analysed for total LDH isoenzymes activity, and compared to samples from 15 patients with normal results. RESULTS: Mean total LDH activity was 33.33 (6.63) U/l. All patients had significantly increased LDH-3 isoenzyme compared to controls. LDH-3 was the predominant fraction, accounting for more than 50% of total LDH activity and present in more than twice the percentage of LDH-1 or LDH-2. By contrast, in the control group, there were high percentages of mainly LDH-1 and LDH-2. CONCLUSIONS: GBS is apparently associated with a distinct LDH isoenzyme pattern in the CSF. More studies are needed to confirm the rise in LDH-3, as serial CSF analyses are unavailable, and to determine the optimum time of analysis when this finding first becomes detectable.     

Lactic dehydrogenase isoenzymes in cerebrospinal fluid of children with Guillain-Barré syndrome

Background: Increased levels of lactic dehydrogenase (LDH) in the cerebrospinal fluid (CSF) have been reported in association with several intracranial pathologies. No studies have been performed on patients with Guillain–Barré syndrome (GBS). Aims: To study LDH isoenzymes in CSF of children with GBS. Methods: CSF samples collected from nine patients with GBS were analysed for total LDH isoenzymes activity, and compared to samples from 15 patients with normal results. Results: Mean total LDH activity was 33.33 (6.63) U/l. All patients had significantly increased LDH-3 isoenzyme compared to controls. LDH-3 was the predominant fraction, accounting for more than 50% of total LDH activity and present in more than twice the percentage of LDH-1 or LDH-2. By contrast, in the control group, there were high percentages of mainly LDH-1 and LDH-2. Conclusions: GBS is apparently associated with a distinct LDH isoenzyme pattern in the CSF. More studies are needed to confirm the rise in LDH-3, as serial CSF analyses are unavailable, and to determine the optimum time of analysis when this finding first becomes detectable.     

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目的探讨小儿骨髓增生异常综合征(MDS)的临床特点。方法回顾性分析同济医学院附属同济医院1991～2005年间收治的94例小儿MDS的幼稚前体细胞异常定位(ALIP)、血清乳酸脱氢酶(LDH)、血红蛋白F(HbF)、血清铁蛋白(SF)以及细胞遗传学与预后的关系。结果94例中难治性贫血(RA)48例(51.1%),难治性贫血伴原始细胞增多(RAEB)26例(27.7%),转化中的难治性贫血伴原始细胞转化增多(RAEBt)20例(21.3%)。44.0%的病例(11/25)检出ALIP,随访中5例转为白血病。9.6%病例(9/94)伴有嗜酸性粒细胞增多,随访中的7例全部死亡,平均存活时间10.5个月。高危组的SF和LDH明显高于低危组,LDH<300U/L组平均存活时间明显长于LDH≥300U/L组。42.9%(9/21)病例伴有细胞遗传学改变,55.6%(5/9)转为白血病。结论小儿MDS伴有SF和LDH的明显升高以及伴有嗜酸性粒细胞增多者预后不良,染色体核型分析对小儿MDS的诊断、预后评估有重要价值。     

LDH-Isoenzyme im Muskel bei neuromuskulären Erkrankungen und bei Konduktorinnen der recessiv X-chromosomalen Muskeldystrophie (Duchenne)

Zusammenfassung Die Untersuchungsserie umfaßt 41 Patienten mit neuromuskulären Erkrankungen (15 recessiv x-chromosomale Muskeldystrophie (MD) Duchenne, 1 recessiv x-chromosomale MD Becker-Kiener, 1 recessiv x-chromosomale scapulo-humero-distale MD, 7 recessiv autosomale MD, 3 kongenitale MD, 9 spinale Muskelatrophien, 5 seltenere neuromuskuläre Erkrankungen) und 26 Konduktorinnen der Muskeldystrophie Duchenne. Muskelbiopsien wurden aus dem M. quadriceps femoris entnommen. Nach Homogenisierung wurden die LDH-Isoenzyme mittels Agargelelektrophorese nach Wieme und Enzymfärbung nach van der Helm identifiziert. Alle Muskelproben wurden lichtmikroskopisch untersucht. Die meisten Patienten mit Duchenne-MD hatten deutliche Veränderungen der LDH-Isoenzyme mit Überwiegen der hybriden Isoenzymfraktionen LDH-2, LDH-3 und LDH-4. Die LDH-5 war vermindert oder fehlte. Es bestand jedoch keine Beziehung zwischen dem Ausmaß der LDH-Isoenzymveränderungen und dem klinischen Stadium oder der Schwere der histologischen Befunde. Ähnliche LDH-Isoenzymmuster wie bei der MD wurden auch bei der spinalen Muskelatrophie und anderen neuromuskulären Erkrankungen gefunden. Weder die genetisch sicheren noch die möglichen Konduktorinnen mit pathologischer Muskelhistologie und erhöhter Serum-CPK-Aktivität zeigten Abweichungen im LDH-Isoenzymmuster. Die Probleme der Interpretation embryonaler LDH-Isoenzymmuster bei neuromuskulären Erkrankungen werden diskutiert.

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Muscle LDH isoenzymes in neuromuscular diseases and in carriers of recessive X-linked muscular dystrophy (Duchenne)

This investigation includes 41 patients with neuromuscular diseases (15 recessive x-linked muscular dystrophy (MD) Duchenne, 1 recessive x-linked MD Becker-Kiener, 1 recessive x-linked scapulo-humero-distal type, 7 recessive autosomal MD, 3 congenital MD, 9 spinal muscular atrophy and 5 rare entities of neuromuscular diseases) and 26 carriers of Duchenne MD. Muscle specimens were taken from the quadriceps muscle. LDH isoenzymes were separated after homogenization by agar gel electrophoresis according to Wieme's method. The isoenzyme fractions were stained by a modified van der Helm technique. Histological examination (light microscopy) was done in all specimens. Most of the patients with MD Duchenne had marked changes in the LDH isoenzyme distribution with predominance of the hybrid fractions LDH-2, LDH-3 and LDH-4. LDH-5 was decreased or absent. There was no relation between the extent of the LDH changes and the clinical stage of disease or histological features. Similar abnormalities were observed in some patients with other types of MD but also in muscular atrophy. Neither the genetically definite carriers nor the possible carriers with elevated serum CPK and histological changes showed abnormalities in the LDH isoenzyme pattern. The problems of interpretation of a fetal-like LDH-pattern in neuromuscular diseases are discussed in respect to the interindividual variability of normal muscle LDH isoenzyme distribution.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

基于决策曲线和剂量反应分析评估乳酸脱氢酶对儿童难治性肺炎支原体肺炎的预测价值

目的 探讨乳酸脱氢酶（LDH）对儿童难治性肺炎支原体肺炎（RMPP）的预测价值。方法 通过倾向性匹配法获得73例RMPP患儿为难治组,146例非难治性的普通MPP患儿为普通组,利用logistic回归、限制性立方样条模型和决策曲线分析评估LDH对RMPP的临床预测价值。结果 难治组和普通组高热发生率、WBC计数、血小板计数、中性粒细胞百分比及血清C反应蛋白、降钙素原、血红蛋白、白蛋白、谷氨酸-丙酮酸氨基转移酶、天门冬氨酸氨基转移酶、LDH含量的比较差异有统计学意义（P < 0.05）。两组鼻咽抽吸物MP-DNA载量及胸腔积液、肺实变、肺不张、气促、皮肤损害发生率的比较差异有统计学意义（P < 0.05）。多因素logistic回归分析显示,高热、血红蛋白水平、LDH水平、肺实变是RMPP发生的独立预测因素（OR分别为10.097、0.956、1.006、3.756,均P < 0.05）。限制性立方样条分析结果显示,LDH连续性变化与RMPP发生的关联强度呈非线性剂量反应关系（P < 0.01）。决策曲线分析显示LDH对RMPP的预测有重要临床价值。结论 LDH是儿童RMPP发生的独立预测因素,与RMPP发生的关联强度呈非线性剂量反应关系。     

Spontaneous remission of Burkitt's lymphoma associated with herpes zoster infection

A 12-year-old white female with recurrent Burkitt's lymphoma had a spontaneous remission associated with a localized herpes zoster infection. The remission lasted nearly 2 months before the tumor recurred in the central nervous system. LDH isoenzyme determinations done on an earlier ovarian tumor and serum at time of bone marrow relapse showed different predominant LDH isoenzyme patterns. These data might be interpreted as showing that different malignant cell clones were responsible for ovarian and bone marrow relapses. Studies to elucidate the mechanism of spontaneous remission at the time of zoster infection demonstrated serum factor(s) which stimulated normal B lymphocytes.     

血清心肌肌钙蛋白I诊断川崎病急性期心肌损伤的临床价值

为探讨血清心肌肌钙蛋白I(cTnI)诊断川崎病(KD)急性期心肌损伤的临床价值。检测KD组(n=40)及对照组(n=23)患儿血清cTnI、肌酸激酶(CK)、肌酸激酶同功酶(CK-MB)、乳酸脱氢酶(LDH)与谷草转氨酶(GOT)浓度。结果显示①KD组与对照组血清CK、LDH、GOT浓度无显著性差别(P＞0.05);而血清cTnI、CK-MB浓度明显高于对照组水平(P＜0.001)。②在诊断KD患儿急性期心肌损伤上cTnI优于CK-MB(P＜0.05),。结果表明cTnI与CK-MB对KD患儿急性期心肌损伤有诊断价值;与CK-MB比较,cTnI具有高特异性、灵敏度。     

后纵隔神经母细胞瘤35例

目的探讨儿童后纵隔神经母细胞瘤的临床特征。方法收集2007年5月-2010年9月北京儿童医院收治的35例后纵隔神经母细胞瘤患儿的临床资料,对患儿肿瘤生物因子[LDH、神经元特异性烯醇化酶(NSE)、24 h尿香草扁桃酸(VMA)]、病理类型、分期及治疗进行回顾性分析。结果 1.本组35例后纵隔神经母细胞瘤患儿年龄4.5个月～16岁(中位年龄2岁6个月)。其中30例小于5岁;病程1 d～5个月。2.临床表现:发热10例(29%),咳嗽12例(34%),发热伴咳嗽5例(14%),纵隔肿物11例(31%),颜面肿物2例(6%),Horner综合征6例(17%)。3.实验室检查:LDH增高25例(71%),LDH<1 500 IU.L-135例;NSE增高24例(73%),正常9例(27%);24 h尿VMA增高9例(28%),正常23例(72%);骨髓细胞学检查10例见菊花团样神经母细胞瘤细胞,骨髓活检8例阳性。4.临床分期:Ⅰ期2例(6%),Ⅱ期7例(20%),Ⅲ期7例(20%),Ⅳ期17例(48%),ⅣS期2例(6%);病理组织学形态依据肿瘤分化程度不同而不同,其中神经节细胞瘤2例(7%),神经节母细胞瘤12例(41%),神经母细胞瘤15例(52%)。5.治疗:35例中22例根据分期及临床危险度分组不同采用化疗、放疗和原发瘤灶切除术综合治疗,其中6例高危组患儿行自体干细胞移植,3例患儿复发,余13例患儿中6例放弃治疗,5例化疗过程中失访,2例ⅣS期随诊观察。结论儿童后纵隔神经母细胞瘤临床多表现为发热、咳嗽或纵隔占位,血LDH增高不明显,尿VMA多数正常,骨髓转移发生率低,病理以神经节母细胞瘤和神经母细胞瘤分化型多见,规律治疗预后较好。     

Lactate dehydrogenase activity is increased in plasma of infants with advanced necrotizing enterocolitis

In infants with necrotizing enterocolitis (NEC), intestinal gangrene defines advanced disease. Since intestinal ischemia is considered a pathogenetic factor for intestinal gangrene, serum activity of mucosal and seromuscular enzymes may be elevated in these patients. Our aim was to evaluate if serum enzymes activity is increased in infants with NEC associated with intestinal gangrene. We performed a retrospective review of the case notes of infants operated on for NEC between 1998 and 2006. Patients with preoperative determination of serum enzymes were included in the study, and were divided into Group A and Group B based on the presence or absence of intestinal gangrene, respectively. Serum activities of alkaline phosphatase (ALP), glutamic oxaloacetic transaminase (GOT), creatine kinase (CK), and lactate dehydrogenase (LDH) were compared in the two Groups. Values are medians (interquartile range). Thirty-five infants were operated on for NEC in the study period. Eighteen patients fulfilled the inclusion criteria: 12 in Group A and six in Group B. Group A patients had significantly higher LDH activity [1131.0 (1092.0-1300.0) vs. 482.0 (440.0-624.5) IU/L; P < 0.005]. Our findings suggest that LDH activity may be increased in infants with NEC and intestinal gangrene. Its evaluation could be a further tool in the surgical decision making process in infants with NEC.     

Studies on the Lactic Dehydrogenase (LDH) during Development

The serum LDH activity and the isozyme patterns in cord blood and the healthy individuals in different age were investigated during the development and the following results were obtained. 1) LDH activity The mean values in each group were as follows: 490.30 u/ml in cord blood, 623.60 u/ml in early newborns (1–3 days), 575.45 u/ml in newborns (4–7 days), 395.00 u/ml in infants (1–6 m), 371.00 u/ml in infants (6–12 m), 342.00 u/ml in young children (1–6 y), 298.24 u/ml in school children (6–15 y) and 212.00 u/ml in adults. Marked elevations of the activity were proved in the newborn group, especially 1–3 days after birth. After the newborn period, the activity gradually decreased to the adult level. No significant differences were obtained between the male and the female in each group. 2) LDH isozyme The distribution dominance of the LDH isozymes in all groups were indicated in the following order: LDH-2>LDH-1>LDH-3>LDH-4>LDH-5. The LDH isozyme pattern in cord blood showed the specific pattern considerably different from those in other groups. The LDH isozyme patterns in newborn serum showed the statistically significant increase of LDH-3, LDH-4 and LDH-5 as compared with those in other age groups and the alteration was marked in the early period of the newborn, 1–3 days after birth. 3) The possible mechanisms of the changes of the serum LDH activity and the alterations of the isozyme patterns were discussed.