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.     

Quantitation of lactate dehydrogenase isoenzyme patterns of the developing human fetus

The differentiation of heart and liver lactate dehydrogenase isoenzymes during embryological development of the human was studied. At the end of 3 mth the percent level of heart monomer in heart and liver were identical. However with further development heart monomers decreased in liver and increased in the heart. The greatest rate of change occurred during the last trimester (7–9 mth) of development, whereby at this time patterns similar to those demonstrable in corresponding adult organs were evident. A similar study involving stillborns suggests the possibility that some of these cases might result from the lack of differentiation of LDH isoenzymes rich in heart monomer.     

Abnormal lactate dehydrogenase isoenzyme pattern in a critically ill patient

We have described a patient who had an abnormal isoenzyme of lactate dehydrogenase in both serum and tissue. The presence of LD6 is indicative of a poor prognosis. Some of the biochemical characteristics of the isoenzyme are (1) LD6 is not an artifact, (2) it contains an M subunit but not an H subunit, and (3) it is not an immunoglobulin complex. We believe LD6 may arise during episodes of severe shock as lysosomes rupture and is either a previously sequestered lysosomal LD or is a lysosomal modification of LD5.     

乳酸脱氢酶同工酶第6条带检测的临床研究

在临床工作中应用改良乳酸脱氢酶(LDH)同工酶试剂盒,检测到乳酸脱氢酶同工酶6(LDH6)条带,对出现LDH6的患者进行追踪检测,发现患者血清LDH总活性都很高,均大于520U/L。同时,当血清LDH6所占总活性比例大于7.9%时,患者2周内即死亡。因此,我们通过改良LDH同工酶试剂检测LDH6酶。可尽快检测出患者肝损伤程度,使其及时得到治疗。     

Specificity of autoantibodies to lactate dehydrogenase isoenzyme subunits

We studied serum from 12 unrelated patients with variant electrophoretic patterns for lactate dehydrogenase (EC 1.1.1.27; LD) isoenzymes characteristic of LD-immunoglobulin complexes. Immunoglobulin class was identified in four cases. In all 12 cases, mixing the patient's serum with control serum altered the mobility of normal LD isoenzymes to that of the variant. To determine antigenic specificity, we mixed ammonium sulfate-precipitated fractions of patient's samples with purified LD1 (H tetramer) or LD5 (M tetramer) prepared by anion-exchange chromatography. In six cases the fractionated antibody displayed a pure M-subunit specificity. In four cases it acted against both M tetramers and H tetramers, and in two cases the antibody affected the migration only of LD isoenzymes containing both M and H subunits (i.e., hybrid isoenzymes). Depending on the relative excess of antibody or LD5 in such mixtures, various different anomalous electrophoretic patterns were produced. These results indicate that apparent differences between variant LD isoenzyme patterns in whole serum of different individuals can arise from autoantibodies with similar reactivities being present in various ratios of antigen to antibody.     

Abnormal serum lactate dehydrogenase isoenzyme in a case of laryngeal carcinoma and thyrotoxicosis.

An abnormal lactate dehydrogenase (LDH) isoenzyme was found in the serum of a patient with laryngeal carcinoma and hyperthyroidism. On electrophoresis it migrated as an additional band between LDH-1 and LDH-2. Follow-up studies suggested that this higher molecular weight, rather thermostable LDH isoenzyme, might have originated from the cancer tissue, though a possible relationship with the thyrotoxic state cannot be excluded.     

Abnormal lactate dehydrogenase isoenzyme in serum and tumor tissue of a patient with neuroblastoma

Serum and tumor tissue of a patient with neuroblastoma contained an abnormal isoenzyme of lactate dehydrogenase (LDH; EC 1.1.1.27), which, on agarose gel electrophoresis, migrated between LDH-2 and LDH-3 with a mobility the same as that of the extra LDH isoenzyme found in normal human erythrocytes. On surgical removal of the tumor, the high total LDH activity (775 U/L) in the serum of the patient rapidly decreased to normal (70-220 U/L), and the abnormal LDH isoenzyme was no longer detected. The total LDH activity of the abnormal LDH isoenzyme per gram of hemoglobin in the tumor tissue was 26 times that of erythrocytes, suggesting that the abnormal isoenzyme originated mainly from the tumor cells themselves rather than the erythrocytes contained in the tumor tissue. This first report on the appearance of the abnormal LDH isoenzyme in a patient with neuroblastoma suggests that this abnormal LDH isoenzyme may have some significance as a marker enzyme for neurogenic tumors.     

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.