Macro lactate dehydrogenase: an LDH-immunoglobulin M complex that inhibits lactate dehydrogenase activity in a patient's serum

A macro lactate dehydrogenase (LDH, EC 1.1.1.27) isoenzyme with a low total LDH activity was present in the serum of a 57-year-old woman with a drug eruption (cutaneous lesions from an allergic reaction to drug administration). The patient's LDH was shown by immunoelectrophoresis to be bound to immunoglobulin G (IgG) and M (IgM). It was found that the patient's IgM acted as an inhibitor of LDH that was specific for the M subunit. When IgM was treated with 0.1 mol/l of 2-mercaptoethanol (2-ME), the inhibiting effect of the IgM to LDH activity disappeared, while treated IgM continued to bind to the LDH molecule. The LDH activity increased approximately two-fold when the patient's serum was treated with 2-ME. LDH activity in normal human serum was inhibited and an abnormal pattern of LDH isoenzyme appeared when the patient's IgM was added to normal serum. The present case seems to be the first report of LDH-IgM complex with a marked decrease of LDH activity.     

毛细管电泳法分离血清中乳酸脱氢酶同工酶

目的利用还原型辅酶I（NADH）在340nm波长处特异性吸收峰，建立用毛细管区带电泳在线检测人血清中乳酸脱氢酶（LDH）同工酶的方法。方法实验中采用未涂层毛细管，长60cm，内径75μm，pH9．4（23℃）二氨基二甲基1，3丙二醇（AM2P）缓冲液含20mmol/L氧化型辅酶I（NAD^＋）、51，6mmol/L乳酸锂。结果在25min内完成电泳分离，乳酸脱氢酶同工酶1（LDH1）、乳酸脱氢酶同工酶5（LDH5）纯品各自均可得到较好峰形，而且LDH1、LDH2纯品的混合物亦可得到完全分离，在分析正常人血清与肝癌患者血清时，其结果与美国Helena公司REP全自动琼脂糖电泳结果一致，取得满意效果。结论该法快速、低耗，具有较好的推广应用价值。     

A transient variant of serum lactate dehydrogenase isoenzymes.

An unusual variant of the serum lactate dehydrogenase (LDH) isoenzyme pattern is described in an apparently healthy young woman. The abnormal pattern consisted of a single zone of LDH activity, having the same mobility as, but more diffuse than, normal LDH-4. The molecular weight of the abnormal LDH complex is approximately 280 000, but the nature of the additional component remains unknown, as the isoenzyme pattern spontaneously reverted to normal six weeks after it was first noticed.     

Automated kinetic determination of lactate dehydrogenase isoenzymes in serum.

A steady-state kinetic method has been revised for measuring lactate dehydrogenase isoenzyme activities, which relates the inhibition of heart-type isoenzyme activity to the overall isoenzyme composition of the enzyme subunits. The method depends on the pH-dependent formation of an inhibitory ternary complex by the heart-type isoenzyme with NAD+ and pyruvate (if the reaction is measured by NADH oxidation). A preincubation step in the previous method is eliminated. The isoenzymes are measured by measuring the reduction of pyruvate in two different concentrations, which favor either the total or fractional activity, depending on the concentrations of pyruvate and the percentage of heart-type subunits. The method has been adapted to a centrifugal analyzer, which has speeded automated isoenzyme determinations, with an accuracy comparable to that for electrophoretic methods.     

Biological variance of total lactate dehydrogenase and its isoenzymes in human serum

We measured the variance components of total lactate dehydrogenase (LD; EC 1.1.1.27) activity and isoenzymes in sera of 24 healthy laboratory staff, ages 23-50 years, over a 12-month period. We used the first six weeks' results to establish baseline values for each analyte in each individual. These values were "normally" distributed for total LD and isoenzymes 1 through 4, but values for isoenzyme-5 were skewed slightly to the left. The overall means and variances determined for the remaining 10 months were not significantly (p greater than 0.05) different from the corresponding baseline values. Average variances (SD2) for the longer-term (10-month) study were: intra-individual, 732, 1.92, 2.25, 1.09, 1.11, and 2.25, and inter-individual, 1988, 5.03, 1.76, 1.57, 1.21, and 2.01 for total LD (U/L) and LD-1 through LD-5 (% of total), respectively. Average long-term analytical variability was less than 35% of the total variance for the five isoenzymes and 6% for total LD, and was characteristic of the individual. There were no significant differences in mean activities with respect to age or sex. All six analytes exhibited slight seasonal variations.     

Photodensitometry of mouse serum lactate dehydrogenase isoenzymes separated on polyacrylamide gel

A photodensitometric method for the quantitative estimation of mouse serum lactate dehydrogenase isoenzymes after electrophoresis on polyacrylamide is described. Polyacrylamide provided better resolution of individual isoenzyme fractions than could be obtained using cellulose acetate support media. Photodensitometry allowed for easier and more accurate quantitation.     

Diagnostic efficiency of lactate dehydrogenase isoenzymes in serum after acute myocardial infarction

Diagnostic efficiency of lactate dehydrogenase isoenzymes were studied in 117 consecutive patients admitted with some symptoms of acute myocardial infarction. The results of lactate dehydrogenase isoenzyme tests were not available to the physicians, who diagnosed the patients according to criteria based on clinical symptoms, electrocardiographic findings and changes in three serum enzymes. Acute myocardial infarction was diagnosed in 41 patients. The diagnostic efficiency of lactate dehydrogenase isoenzyme 1 and the various ratios between this and the other isoenzymes were compared using receiver operating characteristic curves and logistic discriminant analysis. Lactate dehydrogenase isoenzyme 1 was the best parameter on the second day after admission. On that day, calculating the various ratios between isoenzyme 1 and the other isoenzymes did not improve discrimination.     

Use of purified lyophilized human lactate dehydrogenase isoenzymes in a study of the measurement of lactate dehydrogenase activity

We examined the stability of human lactate dehydrogenase (EC 1.1.1.27; LD) isoenzymes 1, 2, and 3--purified to specific activities of about 200 kU/g--when lyophilized in a buffered stabilized matrix of bovine albumin. Each isoenzyme was prepared at two activity concentrations and stored at -20, 4, 20, 37, and 56 degrees C for as long as six months. LD-1 activity decayed with zero-order kinetics, LD-2 and LD-3 with first-order kinetics. The extrapolated half-lives of these preparations at -20 degrees C varied between 80 and 530 years. Stability of reconstituted samples stored at 4 degrees C was excellent for LD-1 but poor for LD-2 and LD-3. We suggest that preparations of human LD-1 be further investigated as a possible reference material.     

Total lactate dehydrogenase and its isoenzymes in serum of patients with non-small-cell lung cancer

Values for total lactate dehydrogenase (LD, EC 1.1.1.27) activity in serum and LD isoenzymes were determined at diagnosis in 273 patients with non-small-cell lung cancer, 85 of whom were in stage 1, 92 in stage 2, and 96 in stage 3. We divided the patients into three groups, based on their total serum LD values: less than 225 U/L (normal reference range), 226-500 U/L, and greater than 500 U/L. Overall values for LD were above normal at diagnosis for 69% of the patients, being moderately increased in 63 patients and highly increased in 125. Eighty percent of the patients in stage 1 had normal values for LD at diagnosis, but 88% of the patients in stage 2 and 94% of the patients in stage 3 had above-normal LD values at diagnosis. In 55% of the patients in stage 2 and 73% of the patients in stage 3, LD activity was highly increased. In the patients with normal values for total LD, the proportions of the LD isoenzymes were normal. In the patients with increased LD, the isoenzyme proportions were increased for LD-4 and LD-5, up to twice the normal values. The sensitivity of LD in detection of lung cancer was 60% for LD at the cutoff point of 250 U/L in comparison with normal controls, and 47% for LD at the cutoff point of 310 U/L in comparison with the benign lung disease group of patients (95% specificity). We conclude that total LD in serum may be a direct indicator of clinical stage and tumor burden in patients with non-small-cell lung cancer.     

蛇毒去纤酶溶栓治疗急性心肌梗死患者乳酸脱氢酶同工酶谱的变化

目的 :观察急性心肌梗死 (AMI)蛇毒去纤酶静脉溶栓治疗后血清乳酸脱氢酶 (L DH)同工酶谱的变化。方法 :采用琼脂凝胶电泳方法系列观察了 41例 AMI患者血清 L DH同工酶谱的改变 ,并与 2 0例正常人和2 7例不稳定型心绞痛患者进行比较。结果 :在 AMI患者中 ,蛇毒去纤酶治疗组 (1 9例 )血清 L DH、CK和 CKMB峰值较常规治疗组 (2 2例 )增高 ;并发现蛇毒去纤酶治疗组 L D4(0 .0 77± 0 .0 2 8)、L D5 (0 .1 2 7± 0 .0 86 )和L D5 / L D4(2 .1 8± 1 .2 9)峰值分别较常规治疗组 L D4(0 .0 39± 0 .0 1 9)、L D5 (0 .0 46± 0 .0 32 )和 L D5 / L D4(1 .32±0 .5 3)明显升高 (P均 <0 .0 1 )、但其它 L DH同工酶之间无显著性差异 (P均 >0 .0 5 )。结论 :蛇毒去纤酶治疗AMI患者有一定的加速心肌酶释放的作用 ,但蛇毒去纤酶还可能对肝脏有损害。