Clinical applications of lactate dehydrogenase isoenzymes

A quantitative electrophoretic test for the determination of lactate dehydrogenase isoenzymes was applied to the analysis of human tissues, cells and fluids in order to obtain their normal isoenzyme patterns and to form a reference record. The same test was employed in the analysis of serum samples from patients with defined pathological conditions. The abnormal serum isoenzyme patterns were correlated with the tissue patterns, thus indicating the origin of the abnormality. This type of correlation, together with the clear demonstration of the actual isoenzymes and their quantitation, improves diagnostic discrimination and enhances the early detection of a biochemical abnormality that aids in the prevention of disease.     

Thrombocyte lactate dehydrogenase isoenzymes in patients with ischemic stroke

It was established that in the acute period of the ischemic stroke in the maiority of cases a change of isoenzyme structure of LDG thrombocytes was due to a decrease of LDG3 activity. In a number of patients the dominant change in the spectrum was determined by LDG and LDG4 fractions. The changes were of a stable character up to 10 weeks. LDG4 increase was characteristic of the isoenzymes spectrum in the patients with a severe development of the disease and in the patients in the remote period of the stroke. The obtained data can serve as a criterion for evaluating the adaptive changes in acute brain ischemia.     

Serum activities of hydroxybutyrate dehydrogenase (HBD) and the isoenzymes of lactate dehydrogenase (LD) as an index of traumatic brain injury

The lactate dehydrogenase (LD), the hydroxybutyrate dehydrogenase (HBD), and the LD isoenzyme activities in serum were followed in the posttraumatic period in 113 patients with cranio-cerebral injury, 70 of whom had verified brain contusion--laceration. In patients with brain contusion the HBD activity, known to be exerted mainly by the anodal LD isoenzyme fractions dominating in brain tissue, was significantly raised in 91% of the blood samples taken within four hours, and in 92% of the samples taken between 12 and 24 hours after trauma, while it was within normal limits in all the samples taken within four hours in patients with brain concussion, and increased in only 17% of the concussion patients 12-24 hours after trauma. The LD1 and the LD1+2 activities were of less diagnostic importance in blood samples taken during the first 24 hours. However, after 24 hours the LD1 activity was as informative as the HBD activity. The LD1 activity was normal in all concussion patients from the third day after trauma, while 78% of the contusion patients still showed raised LD1 activity then. The determination of HBD activity in serum in the immediate post-traumatic period is recommended as an appropriate method for screening parenchymatous brain injury. A complete LD isoenzyme separation may later add some further information in doubtful cases.     

Isoenzyme spectra of lactate dehydrogenase in tissues of pigs at different stages of embryonic development

Dynamics of the activity and correlation of isoenzyme spectra of lactate dehydrogenase in extracts of the liver, hip muscle and blood serum of the 30-60- and 108-day pig embryos was studied by polyacrilamide gel diskelectrophoresis. A high specificity of isoenzymes sets in all the tissues under study is established.     

Molecular weight of cytoplasmic malate dehydrogenase, mitochondrial malate dehydrogenase and lactate dehydrogenase of a freshwater catfish

The multiple molecular forms of cytoplasmic malate dehydrogenase (cMDH), mitochondrial malate dehydrogenase (mMDH) and lactate dehydrogenase (LDH) were studied in the liver and skeletal muscle of the freshwater catfish, Clarias batrachus. There were two electrophoretically distinguishable bands (AA and BB) of cMDH and mMDH which suggests that they are apparently encoded at two gene loci (A and B) in both the tissues. However, the presence of a single band (LDH-1) of LDH in liver and double bands (LDH-1 and LDH-2) in skeletal muscle in which LDH-2 was predominant reflects the differential expression of LDH genes in different metabolic tissues to meet the requirement of energy production. The AA isoform (74 kd) of liver cMDH was smaller than those of the AA form (110 kd) of skeletal muscle. In contrast, the BB isoform of liver (42 kd) and skeletal muscle (54 kd) were more or less similar in size. Unlike the case of cMDH, the molecular weight of AA isoform (115 kd) of liver mMDH was higher than those of the AA form (87 kd) of skeletal muscle. Whereas the molecular weight of BB isoform (58 kd) of liver was in proximity to the weight of BB form (44 kd) of skeletal muscle mMDH. The size of AA isoform (74 kd) of liver cMDH was smaller, while the AA isoform (110 kd) of skeletal muscle was larger as compared to AA form of mMDH in the liver (115 kd) and skeletal muscle (87 kd). But the size of BB isoform of both the isozymes was almost equal in these metabolic tissues.(ABSTRACT TRUNCATED AT 250 WORDS)     

Kinetic analysis of lactate dehydrogenase using integrated rate equations

The reaction catalyzed by lactate dehydrogenase was analyzed under fully second-order conditions using integrated rate equations. A two-step regression analysis was utilized to fit twenty-one progress curves repeated in sextuplicate to the general mechanism second-order integrated rate equation with additional terms of substrate inhibition. The fitting error was less than one percent. The resulting kinetic constants support a ternary complex mechanism; in no case were constants supporting another mechanism predicted. The inhibition constant for oxamate was also determined.     

Effects of early severe malnutrition on heart and skeletal muscle lactate dehydrogenase

Following weaning, rats from litter sizes of 15 to 20 were subjected to severe food restriction for 10 weeks, and compared to rats from litter size 5 fed ad libitum. Percent M (muscle type) lactate dehydrogenase, M and H (heart type) subunit activity and lactate dehydrogenase activity (per g wet weight) determined both electrophoretically and spectrophotometrically were all significantly lower in separated left and right ventricles of the malnourished rats. There were no differences in skeletal muscle lactate dehydrogenase activity. Following 5 weeks of ad libitum feeding, the previously malnourished rats showed large increases in body weight. Now only the right ventricle showed slight decreases in H subunit and lactate dehydrogenase activity; other measurements in the right ventricle and all in the left ventricle had returned to control levels. Skeletal muscle lactate dehydrogenase activity was not different from controls.     

Effects of subunit interactions on the activity of lactate dehydrogenase studied in immobilized enzyme systems

Rabbit muscle lactate dehydrogenase (LDH) was coupled to Sepharose in such a way that each molecule is expected to be attached via only one subunit. Dissociation of the bound active enzyme by several methods all yielded immobilized subunit derivatives which were inactive. These derivatives were capable of regenerating activity by interacting specifically with subunits in solution formed transiently during renaturation. This ability to peck up soluble subunits is lost fairly rapidly upon storage of the immobilized subunits. Similarly, LDH subunits attached to Sepharose via disulfide bonds were found to be inactive. When these subunits were detached from the matrix by mild reduction with mercaptoethanol, activity was regenerated. The kinetics of this reactivation process suggests that reassociation is required for appearance of activity. All these results can be interpreted as showing that subunit interactions are essential for LDH activity.     

Influence of aging and endurance training on lactate dehydrogenase in liver and skeletal muscle

The purpose of this investigation was to determine the effects of aging and endurance training on lactate dehydrogenase (LDH) activity and isozyme pattern in liver and skeletal muscle. Male Fischer 344 rats (n = 30) of three different age groups (young, 4 months; middle-aged, 12 months and old, 22 months) were trained on a treadmill at 75% running capacity for 1 h/day, five times per week for 10 weeks. Age-matched sedentary controls (n = 36) were used for comparison. Total LDH enzyme activity was measured spectrophotometrically; LDH isozymes were separated by native 5.5% polyacrylamide gel electrophoresis and quantified densitometrically. With increasing age, hepatic LDH activity decreased 28%. Old sedentary animals displayed significantly less (22%) hepatic LDH 5 than young and middle-aged animals, and significantly more (40%) hepatic LDH 4 than middle-aged animals. Training resulted in a significant decrease (38%) in total hepatic LDH activity in young rats only. Young animals displayed a significant increase in hepatic LDH 3 (28%), whereas middle-aged animals exhibited a significant decrease in hepatic LDH 3 (40%) with training. No change in total hepatic LDH activity was exhibited in middle-aged or old rats with training. Neither aging or training had a significant effect on LDH activity or isozyme pattern in extensor digitorum longus (EDL). Similarly, LDH activity was maintained in soleus with age, and isozyme pattern was only negligibly affected. We conclude that with age there is a decline in hepatic LDH activity and a decrease in the LDH 5 isozyme. Endurance training induced significant decreases in hepatic LDH activity of young animals. However, these decreases were not a result of shifts in isozymal pattern. Further, LDH activity was maintained in EDL and soleus muscle with age. Finally, endurance training did not have a significant effect on LDH activity or isozymal pattern of EDL or soleus.     

Electron microscopic localization of lactate dehydrogenase in osteoclasts of chick embryo tibia

Lactate dehydrogenase (LDH) was localized in osteoclasts of fixed and unfixed 19-day chick embryo tibias using a copper ferrocyanide capture reaction and osmiophilic polymer generation. This study revealed that: (I) LDH activity in fixed, briefly rinsed osteoclasts was associated principally with limiting membranes of cytoplasmic vacuoles and vesicles and with the plasma membrane; (2) LDH activity in unfixed osteoclasts was associated only with mitochondria; and (3) some mitochondria were stained in fixed tissue given a long rinse. These results indicate that: cytoplasmic LDH diffused out of unfixed tissue; mitochondrial LDH was inactivated by formaldehyde in fixed tissue; and formaldehyde-inhibited mitochondrial LDH can be reactivated by a long rinse. Although the vesicles that stained for LDH activity were found in all parts of the cell, they were concentrated near the ruffled border, and there is evidence that they contained material from the bone surface. These results suggest that the LDH associated with cytoplasmic vesicles of the osteoclasts may be important in processing of material resorbed from the bone surface and that osteoclasts mitochondria may utilize lactate from the bone fluid for energy production.     

Effect of streptomycin on the structure and function of the photoreceptor apparatus of Euglena gracilis

Multiplication stimulating activity (MSA) has been purified from the conditioned media of rat liver cells in culture by a modification of the procedure of Dulak and Temin. Purified MSA stimulates [3H] thymidine incorporation into DNA in subconfluent, serum starved 3T3 cells. Cell cycle analysis by the flow microfluorometer shows that the [3H] thymidine incorporation data reflects DNA synthesis. MSA also stimulates the multiplication of serum starved subconfluent 3T3 cells. MSA is approximately 10-fold less active in 3T3 cells than in chick embryo fibroblasts in stimulating [3H] thymiding incorporation into DNA. MSA causes a 2--10-fold increase in ornithine decarboxylase (ODC) activity in 3T3 cells and the dose response curve parallels the dose response curve for [3H] thymidine incorporation into DNA. The Km of ODC for ornithine is 0.12 mM. There is a 30% decrease in the activity of ornithine transaminase (OTA) during the time period in which MSA causes an increase in ODC activity. Insulin also stimulates [3H] thymidine incorporation into DNA, cell multiplication and ODC activity over the same concentration range as shown for MSA, however, the extent of stimulation by insulin is less than that observed following MSA addition.     

Prognostic value of myocardial lactate dehydrogenase subunit ratio in heart transplant recipients

BACKGROUND: Allograft coronary artery disease (CAD) is a major long-term complication in heart transplant recipients. Unfortunately, methods for early estimation of the likelihood of development of the disease are not currently available. Lactate dehydrogenase (LDH) is composed of heart and muscle subunits. The prevalence of these subunits in LDH isoenzymes (LDH1 through LDH5) is an accurate indicator of myocardial metabolism and allows indirect estimation of oxygen availability to cardiocytes. This study investigated the prognostic value of myocardial LDH composition for the occurrence of morbid events in patients with severe allograft CAD. METHODS: Eighty-eight heart transplant recipients were followed up for a median of 4.3 years. The isoenzymes of LDH and the ratio of the heart and muscle subunits (H/M) were determined in 526 endomyocardial biopsy samples. RESULTS: Eleven patients (12%) died from allograft CAD during follow-up. They had significantly lower H/M ratios compared with event-free patients, with clear differences as early as 6 months after operation. A threshold value of 2.75 was derived from receiver operating characteristic curve analysis. Patients showing H/M values < or =2.75 had a significantly higher mortality rate than did those with higher values (p=.0003). Importantly, the H/M ratio emerged as the most powerful independent prognostic factor of death by allograft CAD (p=.001) in a multivariate model. CONCLUSIONS: Poor myocardial aerobic metabolism estimated through low H/M values was highly predictive of cardiac death resulting from severe allograft CAD. Analysis of LDH isoenzyme profile in routine endomyocardial biopsies might be of clinical value.