Effect of lactate on the effectiveness of glucose and succinate oxidation by myocardium homogenates

Lactate (20 mM) was studied for its effect on the intensity of [1-6-14C] glucose and [1,4-14C] succinate oxidation by the rat myocardial homogenates. It is established that lactate induces specific suppression of aerobic glucose oxidation. A moderate reduction of the succinate and lactate oxidation in their combined incubation is of a non-specific character.     

Effect of lithium salts on lactate dehydrogenase,adenylate kinase,and 1-phosphofructokinase activities

Inhibitions of 30?nM rabbit muscle 1-phosphofructokinase (PFK-1) by lithium, potassium, and sodium salts showed inhibition or not depending upon the anion present. Generally, potassium salts were more potent inhibitors than sodium salts; the extent of inhibition by lithium salts also varied with the anion. Li₂CO₃ was a relatively potent inhibitor of PFK-1 but LiCl and lithium acetate were not. Our results suggest that extents of inhibition by monovalent salts were due to both cations and anions, and the latter needs to be considered before inhibition can be credited to the cation. An explanation for monovalent salt inhibitions is proffered involving interactions of both cations and anions at negative and positive sites of PFK-1 that affect enzyme activity. Our studies suggest that lithium cations per se are not inhibitors: the inhibitors are the lithium salts, and we suggest that in vitro studies involving the effects of monovalent salts on enzymes should involve more than one anion.     

Effect of ruthenium complexes on the activities of succinate dehydrogenase and cytochrome oxidase

In this article, we report the effects of acute administration of ruthenium complexes, trans-[RuCl(2)(nic)(4)] (nic=3-pyridinecarboxylic acid) 180.7 micromol/kg (complex I), trans-[RuCl(2)(i-nic)(4)] (i-nic=4-pyridinecarboxylic acid) 13.6 micromol/kg (complex II), trans-[RuCl(2)(dinic)(4)] (dinic=3,5-pyridinedicarboxylic acid) 180.7 micromol/kg (complex III) and trans-[RuCl(2)(i-dinic)(4)]Cl (i-dinic=3,4-pyridinedicarboxylic acid) 180.7 micromol/kg (complex IV) on succinate dehydrogenase (SDH) and cytochrome oxidase (COX) activities in brain (hippocampus, striatum and cerebral cortex), heart, skeletal muscle, liver and kidney of rats. Our results showed that complex I inhibited SDH activity in hippocampus, cerebral cortex, heart and liver; and inhibited COX in heart and kidney. Complex II inhibited SDH in heart and hippocampus; COX was inhibited in hippocampus, heart, liver and kidney. SDH activity was inhibited by complex III in heart, muscle, liver and kidney. However, COX activity was increased in hippocampus, striatum, cerebral cortex and kidney. Complex IV inhibited SDH activity in muscle and liver; COX activity was inhibited in kidney and increased in hippocampus, striatum and cerebral cortex. In a general manner, the complexes tested in this work decrease the activities of SDH and COX in heart, skeletal muscle, liver and kidney. In brain, complexes I and II were shown to be inhibitors and complexes III and IV activators of these enzymes. In vitro studies showed that the ruthenium complexes III and IV did not alter COX activity in kidney, but activated the enzyme in hippocampus, striatum and cerebral cortex, suggesting that these complexes present a direct action on COX in brain.     

A quantitative histochemical study of lactate dehydrogenase and succinate dehydrogenase activities in the membrana granulosa of the ovulatory follicle of the rat

Using a microdensitometer, lactate dehydrogenase and succinate dehydrogenase activities were measured in the membrana granulosa of the rat ovulatory follicle. Ovaries were removed on each day of the oestrous cycle; oestrus, dioestrus-1, dioestrus-2, and proestrus; and enzyme activities measured in the membrana granulosa as a whole and in four regions within it: peripheral (PR), antral (AR), cumulus oophorus (CO) and corona radiata (CR). Throughout the cycle, lactate dehydrogenase activity was greatest in PR. On oestrus, lactate dehydrogenase activity was progressively less in AR, CO and CR. On dioestrus-1, activity was identical in AR and CO and less in CR. On dioestrus-2, activity was greater in AR than in CO or CR. By proestrus, activity was equal in AR, CO and CR. In the membrana granulosa as a whole, and in each region, lactate dehydrogenase activity declined as ovulation approached. In contrast, succinate dehydrogenase activity in the membrana granulosa as a whole and in PR was constant throughout the cycle. Activity fluctuated in the other regions. Succinate dehydrogenase activity on oestrus was greatest in PR, less in AR and CO and least in CR. On the remaining days, succinate dehydrogenase activity was greatest in PR and less but equal in the remainder of the membrana granulosa.     

Separation of NADH-fumarate reductase and succinate dehydrogenase activities in Trypanosoma cruzi

A recent review suggested that the activity of NADH-fumarate reductase from trypanosomatids could be catalyzed by succinate dehydrogenase working in reverse (Tielens and van Hellemond, Parasitol. Today 14, 265-271, 1999). The results reported in this study demonstrate that the two activities can easily be separated without any loss in either activity, suggesting that fumarate reductase and succinate dehydrogenase are separate enzymes.     

Effect of oxygen and endotoxin on lactate dehydrogenase release, 5-hydroxytryptamine uptake, and antioxidant enzyme activities in endothelial cells

We compared the effects of 95% O2 (hyperoxia) alone, endotoxin (20 ng/ml) alone, and 95% O2 plus endotoxin on the release of lactate dehydrogenase (LDH), uptake of 5-hydroxytryptamine (5-HT), and antioxidant enzyme activities in porcine pulmonary arterial and aortic endothelial cells in monolayer culture. Hyperoxia increased LDH release and decreased 5-HT in both endothelial cell types. Hyperoxia also caused a decrease in catalase (CAT) activity and an increase in total superoxide dismutase (SOD) and glutathione reductase (GSH-Red) activities in both cell types. Endotoxin alone had no effect on LDH release, 5-HT uptake, or antioxidant enzyme activities. However, endotoxin prevented the hyperoxic increase in LDH release and the hyperoxic decrease in 5-HT uptake. Endotoxin plus 95% O2 had no consistent effect on the antioxidant enzyme profile in pulmonary artery or aortic endothelial cells. These results indicate that (1) hyperoxia injures both pulmonary artery and aortic endothelial cells in culture and causes changes in the antioxidant enzyme profile that are similar in the two cell types; (2) hyperoxia-induced decreases in CAT activity and increases in SOD activity may be responsible for increased sensitivity of endothelial cells to O2 toxicity; and (3) endotoxin protects against hyperoxic injury to endothelial cells in vitro, but increases in antioxidant enzyme activities are not the mechanism for this protection.     

Effect in vitro of benthiocarb on rat brain succinate dehydrogenase

Kinetic study of succinate dehydrogenase (SDH) was studied in the brain of albino rat to elucidate the interaction of benthiocarb, an organocarbamate with oxidative metabolism. The significant decrease in maximal velocity (Vmax) without appreciable change in Michaelis-Menten constant (Km) indicates that benthiocarb did not affect or interfere with succinate oriented sites on the enzyme and the inhibition is of a classical non-competitive type.     

Effect of the carbon source and cyclic AMP on isocitrate dehydrogenase, succinate dehydrogenase, and malate dehydrogenase in Klebsiella pneumoniae C3

When strain C3 of Klebsiella pneumoniae is grown on a minimal medium with excess glucose, isocitrate dehydrogenase, malate dehydrogenase, and succinate dehydrogenase specific activities increase in the last period of the exponential growth phase and in the beginning of the stationary phase. Glucose exhaustion does not alter the development of malate dehydrogenase and succinate dehydrogenase, but specific activities are higher than those obtained with excess glucose. In contrast, glucose exhaustion can be correlated with a decrease of isocitrate dehydrogenase specific activity in the stationary phase. Induction of strain C3 isocitrate dehydrogenase by glucose in complex medium and repression by cAMP in mineral medium were observed. Glucose induction and the NADP/NADPH ratio are suggested as regulatory mechanisms controlling isocitrate dehydrogenase synthesis in the Enterobacteriaceae, but the former appears to be restricted to some Klebsiella strains.     

Microquantitative determination of lactate dehydrogenase isoenzymes in the myocardium and the conducting system

Summary A newly developed technique was used for the electrophoretic separation of lactate dehydrogenase (LDH) isoenzymes from lyophilized tissue samples in the nanogram range. In this study portions of 10–200 ng from the myocardium and the conducting system of cattle, sheep, pig and man were microdissected and analysed.In the heart tissues of cattle, sheep and pig, the isoforms LDH1, LDH2 and LDH3 were detected in species-specific varying amounts. In all these animals, the conducting system is marked by high LDH1 activity, which is present at a ratio of about 2:1 compared with the myocardium. The values in man, however, differ from these values, but this might be due to post-mortem changes. The findings are discussed with respect to possible aerobic-anaerobic functions.     

Effect of cisplatin on mitochondrial protein, glutathione, and succinate dehydrogenase in Dalton lymphoma-bearing mice

Cisplatin treatment of tumor-bearing mice resulted a significant decrease of protein in the tissues studied (liver, kidney, and Dalton lymphoma) and also in their mitochondrial fractions. As compared to respective tissues, the protein decrease was noted to be more conspicuous in their mitochondrial fractions. Similarly, mitochondrial glutathione also decreased significantly in the tissues. However, succinate dehydrogenase activity was selectively decreased in the kidney and Dalton lymphoma cells, whereas in liver it remained almost unchanged. An increase in serum urea concentration and kidney mitochondrial lipid peroxidation was also observed after cisplatin treatment. It is suggested that the cisplatin-induced biochemical changes in mitochondria involving mitochondrial protein, glutathione, and succinate dehydrogenase could be the important potent cellular sites contributing to toxicity/cytotoxicity after cisplatin treatment. This revised version was published online in July 2006 with corrections to the Cover Date.     

Changes in the activities of enzymes, especially lactate dehydrogenase, in endotoxin-poisoned mice.

Carbohydrate metabolic disorders were investigated by means of enzyme activities in mice (ddYS) injected intraperitoneally with endotoxin from Salmonella typhimurium. The mice exhibited hyperglycemia 2 hr after administration of endotoxin and hypoglycemia at 18 hr. Activity of hepatic phosphorylase in the endotoxin-poisoned mice at 2 hr was slightly higher than that in the control mice, whereas the level of this activity was not significantly different from that in the controls after 18 hr. Glucose-6-phosphatase activity in the poisoned mice increased by 2 hr after injection, but decreased by 18 hr. The blood lactate level in the poisoned mice transiently decreased until 3 hr after injection, but the mice exhibited a marked lactacidemia by 8–24 hr. The time course of lactate dehydrogenase (LDH) activity in various tissues was examined in mice injected with endotoxin. The activity of hepatic LDH declined to about two-thirds of that of the control mice after 16 hr, and was restored to the normal level by 48 hr. LDH in the cardiac muscle was markedly activated (by about 37%) in the early period (3–6 hr) after administration of endotoxin, and this activity gradually declined. However, the activity of LDH in the skeletal muscle showed a tendency similar to the rise and fall of the levels of blood lactate, and was restored to the normal value at 72 hr after injection. On the other hand, the serum LDH activity in the poisoned mice increased about 1.75-fold by 16 hr after injection. Mice injected with endotoxin exhibited a leakage of the isozymes LDH 3 and 5, but the origin of the leakage is uncertain. Similar elevation in the activities of transaminases (GPT and GOT) and malate dehydrogenase was found in the mouse serum at 16 hr after injection of endotoxin.