Immunochemical properties of immunoglobulin G conjugated with lactate dehydrogenase

Quantitative binding affinities of immunoglobulin G (IgG) for the five isoenzymes of lactate dehydrogenase (LD; EC 1.1.1.27) were determined for IgG isolated from three patients' sera that contained LD-IgG complexes. These three IgGs formed soluble complexes with four (LD 1, 2, 3, 5) of the five LD isoenzymes in two of the patients and in the third they bound with three (LD 2, 3, 4) of the five LD isoenzymes without inhibiting the enzyme activity or precipitating with the enzyme molecules. When rabbit antibody to human IgG was added to these sera, the complexes between the LD isoenzymes and the patients' isolated IgG were completely precipitated. The equilibrium constants for the respective isolated IgG complexes with LD-3 were 0.102, 2.58, and 7.49 X 10(8) L/mol. In these three cases, LD-3 evoked the strongest response from the prepared IgG, demonstrating that the site of antigen recognition of LD-linked IgG was not associated with the structure of individual H and M subunits.     

Complexes of lactate dehydrogenase and immunoglobulin G in human serum

Three patients with electrophoretically abnormal serum lactate dehydrogenase (LDH) isoenzyme patterns due to the presence of LDH-IgG complexes are described. It was found that normal LDH isoenzymes had been complexed with an anomalous immun oglobulin. Concerning the relation of the anomaly with a clinical disorder no definite conclusions could be drawn, although there are some indications that a relation exists between the occurrence of the LDH-IgG complexes and an autoimmune disease.     

Serum lactate dehydrogenase isoenzymes linked to immunoglobulin A

Electrophoretically abnormal serum LDH isoenzyme patterns due to the presence of LDH-IgA complexes are described. Evidence was obtained indicating that the complex formation is caused by the presence of an anomalous immunoglobulin A.     

A case of immunoglobulin G conjugated with lactate dehydrogenase, producing both loss of enzyme activity and an abnormal isoenzyme pattern

We present a patient with an inhibitor of lactate dehydrogenase (LD; EC 1.1.1.27) in serum, who had pericarditis and myocardial hypertrophy. The patient's LD activity in serum was low and the LD isoenzyme pattern was abnormal. The relative molecular mass of this abnormal LD-IgG complex was approximately 490 000. The patient's IgG reacted with all five LD isoenzymes.     

Reversible loss of lactate dehydrogenase isoenzymes and lactate dehydrogenase activity in patient's serum

An abnormal lactate dehydrogenase (LD; EC 1.1.1.27) electrophoretogram (only one band, at the application site) and a low LD activity (7 U/L) was seen for a patient's serum during storage at 22 and 4 degrees C. Both reverted to normal when the serum was incubated at 37 degrees C.     

An automated colorimetric method for the estimation of lactate dehydrogenase activity in serum

An automated method for estimating lactate dehydrogenase (LDH) in serum is presented. Fe3+ is reduced to Fez+ by NADH formed when lactate is oxidized to pyruvate. Fe2+ complexed with 2,2-bipyridyl is measured colorimetrically. Solutions of Fe2+ salt are used as standards. Nicotinamide is used to stabilize NAD+ in solution and is shown to enhance enzyme activity. The method is less expensive than most automated methods published and reagents are stable for at least 4 weeks. Results correlate well with a kinetic spectrophotometric method.     

Lactate dehydrogenase inhibition by immunoglobulin G in human serum

Low lactate dehydrogenase (LD; EC 1.1.1.27) activity and an abnormal LD pattern in electrophoretograms of LD isoenzymes in the sera of two patients were caused by inhibition of LD by immunoglobulin G. One of these showed inhibitor activity in the serum upon direct analysis, while the other showed activity only after the immunoglobulin was stripped from the LD. As judged from the LD isoenzyme patterns in serum, the LD inhibitor appeared to act against M subunits. However, quantification of binding affinities to each isolated isoenzyme showed that the LD inhibitor had a stronger effect on LD isoenzymes 2 and 3 (H3M1 and H2M2, respectively).     

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.     

Use of purified lyophilized human lactate dehydrogenase isoenzyme 5 in a study of measuring lactate dehydrogenase activity

We examined the stability of human lactate dehydrogenase (EC 1.1.1.27) isoenzyme 5--purified to a specific activity of about 400 kU/g--when lyophilized in a buffered, stabilized matrix of bovine albumin. This isoenzyme was prepared with a final activity of about 500 U/L and stored at -20, 4, 20, 37, and 56 degrees C for as long as six months. This isoenzyme decayed with approximate first-order kinetics, with an estimated half-life at -20 degrees C of about 475 years. Stability of reconstituted samples stored at 20 or 4 degrees C was poor, suggesting that the reconstituted material should be used without delay; material stored at -20 degrees C showed excellent stability for 15 days. We propose that such preparations might be further investigated as standards for use in electrophoresis of lactate dehydrogenase isoenzymes.     

Determination of lactate dehydrogenase activity using Warburg's optic test

A method for measuring the total lactate dehydrogenase activity has been developed on the basis of Warburg's optic test with a photoelectrocolorimeter, making use of lactate as a substrate. The results are calculated from the mean molar coefficient of light absorption. The coefficient of variations of the method is 7.7%. The results obtained with the use of a spectrophotometer and photoelectrocolorimeter have been in good correlation. The described technique is recommended as a method of choice.     

Serum lactate dehydrogenase activity ratios with different substrates.

1. The lactate dehydrogenase activity of 89 sera from patients suffering myocardial infarction and of 55 sera from patients with hepatocellular damage was assayed under optimal conditions using pyruvate, alpha-oxobutyrate, hydroxypyruvate and glyoxylate as substrates. Activity was also measured with lactate as substrate at different pH values. 2. The ratios of activities under these different assay conditions were calculated for both series of patients. Correct differentiations for single ratios ranged from virtually nil for hydroxypyruvate/alpha-oxobutyrate to is greater than 93 per cent for glyoxylate/hydroxypyruvate and glyoxylate/alpha-oxobutyrate. This was little improved by the use of multiple ratios involving up to seven separate assays. 3. The activity ratio of hydroxypyruvate to pyruvate which is consistently greater than unity was found to be inverted in a case of morphine poisoning.     

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.     

Association between sedentary behavior and normal-range lactate dehydrogenase activity

Objectives: Recent research demonstrates that lactate dehydrogenase (LDH) activity within the normal range may serve as a mediator in the (positive) relationship between physical activity and cardiovascular disease risk. Emerging work supports deleterious associations between sedentary behavior and health, independent of physical activity. Thus, this study evaluated if sedentary behavior was associated with normal-range LDH activity, independent of physical activity.

Methods: Data from the 2003–2006 NHANES were used (N = 2,087 adults; 40–79 yrs). LDH activity levels were estimated from a blood sample using LX20 and LDH reagent; participants were included if they had LDH activity levels within the normal range (105–333 IU/L). Physical activity and sedentary behavior were assessed via accelerometry.

Results: Sedentary behavior was inversely associated with normal-range LDH activity when physical activity was excluded from the model (OR = 0.89; 95% CI: 0.83–0.97, P = 0.009 for LDH activity quartile 4 vs. 1). However, sedentary behavior was no longer associated with normal-range LDH activity after controlling for physical activity and other covariates (OR = 1.00, P = 0.49 for LDH activity quartile 2 vs. 1; OR = 1.00, P = 0.72 for LDH quartile 3 vs. 1; and OR = 0.99, P = 0.36 for LDH quartile 4 vs. 1).

Conclusion: Unlike physical activity, sedentary behavior is not independently associated with normal-range LDH activity.