Effect of thyroxine on the lactate dehydrogenase isoenzyme composition of chicken tissues in ontogeny

Using disc electrophoresis in polyacrylamide gel, studies have been made on the content of isoenzymes of lactate dehydrogenase in the mitochondria and cytoplasm from the brain, heart and liver after thyroxine administration to embryonal, early postnatal and adult hens. After this administration, the isoenzymic composition becomes more complex, redistribution of separate isozymes being observed in ontogenesis. The level of aerobic form of LDH increases at early stages of ontogenesis, that of anaerobic ones--in adult birds. Basing on their different functional role due to the presence of H- and M-subunits, it may be suggested that thyroxine administration results in a compensatory increase of the oxidative or glycolytic processes at the corresponding stages of ontogenesis, these changes reflecting phylogenetic peculiarities of the formation of the hormonal control of lactate dehydrogenase in tissues of birds.     

Prenatal changes of lactate dehydrogenase isoenzyme patterns and activity in bovine tissues.

Isoenzyme patterns, total lactate dehydrogenase (LDH, E.C. 1.1.1.27) activity and H and M subunit activity were determined in the tissues of Czech Spotted bovine foetuses. Total LDH activity rose in the skeletal muscles throughout the whole of the prenatal period. In the viscera it usually attained the maximum at a foetal length of 66.7 cm. Differences in the isoenzyme patterns of the various organs of an 8.1-cm foetus were relatively small (41.9--66.1% H subunits). In the heart and kidneys, in which LDH1 and LDH2 markedly predominate in adulthood, the isoenzyme pattern resembled the adult one at a length of only 13.3 cm, but in the liver, spleen and lungs not until 66.7 cm. The proportion of H subunits also rose in the part of the gastrointestinal tract where secretory and resorptive activity predominate (the abomasum, the small and the large intestine). Conversely, it fell in organs concerned mainly with the mechanical processing of food (the rumen, reticulum and omasum). The proportion of M subunits rose in all the skeletal muscles up to a foetal length of 66.7 cm. Later on, differentiation into muscles in which M subunits predominated (the longissimus dorsi and the triceps brachii), into muscles with approximately the same proportion of H and M subunits (the iliopsoas) and to muscles with a preponderance of H subunits (the masseter and the muscular part of the diaphragm) occurred.     

Properties of the testicular lactate dehydrogenase isoenzyme.

1. Studies were carried out with pure lactate dehydrogenase isoenzymes C4 (LDH isoenzyme X), B4, (LDH isoenzyme 1) and A4 (LDH isoenzyme 5) isolated from mouse testis, heart and muscle tissue respectively; with LDH isoenzyme X purified from pigeon testes and with crude lysates of spermatozoa from man, bull and rabbit. 2. LDH isoenzyme X from all species showed greater ability than the other isoenzymes to catalyse the NAD+-linked interconversions of 2-oxobutanoate into 2-hydroxybutanoate and of 2-oxopentanoate into 2-hydroxypentanoate. 3. Mouse LDH isoenzyme X presented the broadest spectrum of substrate specificity. It exhibited very similar Km values for a variety of 2-oxo acids: 2-oxopropanoate (pyruvate), 2-oxobutanoate, 2-oxo-3-methylbutanoate, 2-oxopentanoate, 2-oxo-3-methylpentanoate, 2-oxo-4-methylpentanoate, 2-oxohexanoate and 2-oxo-3-phenylpropanoate (phenylpyruvate). The corresponding 2-hydroxy acids were also readily utilized in the reverse reaction. A strong inhibition by substrate and product was demonstrated for the direct reaction. 4. Intracellular distribution of LDH isoenzyme X was investigated in mouse testes. LDH isoenzyme X activity was located in the fraction of "heavy mitochondria" and in the soluble phase. 5. A possible functional role for LDH isoenzyme X is proposed: the redox couple-2-oxo acid-2-hydroxy acid could integrate a shuttle system transferring reducing equivalents from cytoplasm to mitochondria.     

Analysis of total lactate dehydrogenase isoenzyme activity in mouse ova during clevage]

The total activity of lactate dehydrogenase isoenzymes was detected in the intact ova of mice during the clevage and, in particular, blastomeres at the 2-cell stage. Routine histochemical technique was employed in addition to microspectrometry. During the clevage, the ova differ in their enzyme activity. At the 2-cell stage there are ova with similar reaction in both the blastomeres as well as those with different enzyme activity in each blastomere.     

Serum lactate dehydrogenase isoenzyme pattern in non-Hodgkin's lymphomas

Serum lactate dehydrogenase (S-LDH) and its isoenzyme pattern were assayed in 63 non-Hodgkin's lymphoma (NHL) patients, 37 at diagnosis, 15 at relapse and 11 in complete remission (CR). S-LDH in NHL patients with active disease was higher than in normal subjects and CR patients (p less than 0.001). Among the isoenzymes, LDH-2 and LDH-5 showed no remarked differences; LDH-1 was reduced and LDH-3 and LDH-4 raised in comparison to the normal group (p less than 0.001). S-LDH levels and isoenzymes 1 and 4 were influenced by the stage, the histological subgroup and by the presence of general symptoms. In fact, cases in stage IV, with "high-grade malignancy" and with general symptoms, had higher S-LDH levels and more evident LDH-1 and LDH-4 changes than the other stages, the other histopathological subgroups and the cases classified as "A". S-LDH was the same as in normal subjects in the "low-grade" and "intermediate-grade" malignancies as was LDH-1 in stage II and LDH-4 in stages II and III, in "low-grade" malignancy and in the A cases. In contrast, LDH-3 was always high, with no significant difference in relation to the variables considered. Thus, in NHL, LDH-3 seems to be a reliable marker of the presence of the disease in any case, whereas S-LDH is more related to the spread of the lymphoma.     

Further insights into the isoenzyme composition and activity of glutamate dehydrogenase in Arabidopsis thaliana

Following the discovery that in Arabidopsis, a third isoenzyme of NADH-dependent glutamate dehydrogenase (GDH) is expressed in the mitochondria of the root companion cells, we have re-examined the GDH isoenzyme composition. By analyzing the NADH-GDH isoenzyme composition of single, double and triple mutants deficient in the expression of the three genes encoding the enzyme, we have found that the α, β and γ polypeptides that comprise the enzyme can be assembled into a complex combination of heterohexamers in roots. Moreover, we observed that when one or two of the three root isoenzymes were missing from the mutants, the remaining isoenzymes compensated for this deficiency. The significance of such complexity is discussed in relation to the metabolic and signaling function of the NADH-GDH enzyme. Although it has been shown that a fourth gene encoding a NADPH-dependent enzyme is present in Arabidopsis, we were not able to detect corresponding enzyme activity, even in the triple mutant totally lacking NADH-GDH activity.     

Changes in the lactate dehydrogenase isoenzyme spectrum during T-lymphocyte differentiation

The pattern of lactate dehydrogenase isoenzyme spectrum changes on different stages of T-lymphocyte differentiation was studied An enriched population of stem cells has LDH-5, 4 and 3 isoenzymes, and much less LDH-2 activity. The isoenzyme pattern of thymic cell precursors consists of LDH-5, 4, 3 and 2. All the five LDH isoenzymes were found in cortical thymocytes. Medullary thymocytes reveal LDH-5, 4 and 3 isoenzymes. T-lymphocytes of peripheral lymphoid organs contain mainly LDH-5 and in a lesser degree LDH-4 activity.     

Changes in lactate dehydrogenase and glucose-6-phosphate dehydrogenase activity in the course of muscle alteration]

Changes of outflux, extractability and activity of lactate dehydrogenase (LDG) and glucose-6-phosphate dehydrogenase (G-6PhDG) of muscles under the action of heating (at 32--44 degrees for 15 min) and urea (1 M during 10 min, 30 min, 2 hr. and 9 hr.) on the skeletal muscles of R. temporaria L. were studied. Under the thermal action not accompanied by contracture and fall of the excitability (32--36 degrees), the increase of outflux of LDG out of muscles into surrounding solutions is observed. G-6-PhDG in the external medium under any heating action was not revealed. Extractibility of LDG and G-6-PhDG did not change. Under the thermal action accompanied by the fall of excitability and by the contracture, along with the prolong increase of outflux of LDG, a decrease of extractability of LDG takes place. The decrease of G-6-PhDG is set at 42 degrees. Under the alteration of muscles by urea in the period of the temporary fall of excitability and contracture (10 and 30 min) an increase of the outflux of LDG out of muscles is observed. G-6PhDG in the surrounding medium was not revealed up to 9 hr. of incubation of muscle. In the period of the recovery of the excitability and relaxation of muscles (2hr.) the outflux of LDG approaches the control level. During the temporary loss and recovery of excitability, the extractability of LDG and G-6-PhDG does not change. In the period of irreversible contracture and loss of the excitability (6--10 hr.) a sharp increase of outflux of LDG out of muscles takes place. The extractability of the examined enzymes, especially of LDG, decreases.     

Change in the percent of lactate dehydrogenase isoenzyme level in testes of animals exposed to superhigh frequency radiation

The content of six lactate dehydrogenase isoenzymes in testes of rats exposed to electromagnetic field of 3-cm wavelength range was studied. The changes in their percent contents were found to be inhomogeneous compared with control. It is assumed that electromagnetic radiation affects the organs of the human urinogenital system. The results can be used for estimating the safety of persons professionally exposed to electromagnetic radiation of the industrial frequency range and in the therapy of diseases of the urinogenital system.     

Genetic regulation of the lactate dehydrogenase isoenzyme spectrum in mouse erythrocytes

The pattern of lactate dehydrogenase isozymes was investigated by means of electrophoresis in erythrocytes of CBA/Lac and DBA/2J mice homozygous for b and a alleles of the Ldr-1 locus. It is found that differences in the pattern of LDH isozymes, homozygous for the genes Ldr-1a and Ldr-1b, consist in increased activity of the isozyme LDH-4 in mice homozygous for the gene Ldr-1a (DBA/2J) within 12-14 days of postnatal development. Inhibition of the reaction between 125I-LDH-1 and the respective antibodies has demonstrated that increased LDH-4 activity during development is related to the higher content of B-subunits of LDH. It is suggested that the mechanism of the action of the gene Ldr-1 involves changes in the rate of the synthesis and degradation of B-subunit of LDH.     

Correlation of lactate dehydrogenase isoenzyme C4 activity with the count and motility of human spermatozoa.

The activity of lactate dehydrogenase isoenzyme C4 was determined on 90 human semen samples. The correlation between the isoenzyme activity and sperm count and motility was good (r = 0.74 for values of U/ml semen against sperm count).