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At least 19 recordsLinked to original sources
PubMed1979

Lactate-to-pyruvate or pyruvate-to-lactate assay for lactate dehydrogenase: a re-examination.

The pyruvate-to-lactate assay for determining lactate dehydrogenase (EC 1.1.1.27) can now yield linearity equal to or better than that obtained by the lactate-to-pyruvate assay. In addition, there are significant advantages to the pyruvate-to-lactate reaction: (a) a greater change in absorbance per unit time, which allows more accurate spectrophotometric readout; (b) lower reactant concentrations are required, which substantially reduces the cost per assay; (c) solid reagents are used to prepare the assay solution; and (d) reagent solutions are more stable. However, impurities present in commercial NADH preparations may substantially affect measured lactated dehydrogenase activities; therefore, a Standard Reference Material for NADH is being developed for issuance by the National Bureau of Standards.

L-Lactate Dehydrogenase↗
PubMed1978

Optimal conditions and comparison of lactate dehydrogenase catalysis of the lactate-to-pyruvate and pyruvate-to-lactate reactions in human serum at 25, 30, and 37 degrees C.

We report optimal conditions for assaying highly purified human lactate dehydrogenase isoenzymes with the lactate-to-pyruvate and pyruvate-to-lactate reactions, as they apply to human serum. Interconversion of results between reactions is not practicable. Measurements of lactate dehydrogenase in either reaction direction at 25, 30, or 37 degrees C can be equally reliable if the volume fraction and the resulting deltaA/min is small. However, for interinstrument and interlaboratory comparisons, results from the lactate-to-pyruvate reaction are more reliable.

Buffers↗
PubMed1977

Optimal conditions for assaying human lactate dehydrogenase by the lactate-to-pyruvate reaction: Arrhenium relationships for lactate dehydrogenase isoenzymes 1 and 5.

Optimal reaction conditions to sassay human lactate dehydrogenase (lactate-to-pyruvate) were established for isoenzymes 1 and 5 at 25, 30, and 37 degrees C in diethanolamine and 2-amino-2-methyl-1,3-propanediol. Different substrate concentrations are required at each temperature. The conditions permit measurement of lactate dehydrogenase 1 and 5 with the lowest substrate concentrations that allow for the highest equal sustainable efficiency in measuring both isoenzymes. About 95% of each isoenzyme activity is measured if the assay is performed within the first minute after the reaction is initiated even for activities as high as triple the upper limit of normal. The Arrhenius relationship is different for each isoenzyme, but results obtained for each at one temperature can be compared with results at another temperature by use of simple conversion equations. Assays at 25 and 30 degrees C are more economical and less variable than assays at 37 degrees C.

Buffers↗
PubMed1979

Lactate elimination in man: effects of lactate concentration and hepatic dysfunction.

Lactate elimination was studied in twenty-six healthy volunteers during primed constant lactate infusion or multiple lactate injection tests, at blood lactate concentrations of 1-8 mmol-1. Although lactate elimination fitted a single exponential curve over a 30 min period, a significant correlation between the rate removal constant (KL) and the peak blood lactate concentration (Lphi) was demonstrated: loge KL = -2.43-0.132 Lphi (P = 0.003, r = 0.63, n = 20) This suggests that lactate removal does not follow first order kinetics over a wide concentration range but becomes saturated at relatively low blood lactate concentrations. Estimates of the lactate distribution volume did not differ significantly at different dosage levels, but remained in the range 270-300 ml kg-1. Skeletal muscle uptake accounted for about 26% of the infused lactate load. Seven patients with well-compensated hepatic cirrhosis were compared with a group of six control subjects during primed constant infusion tests. Fasting and steady state blood lactate concentrations achieved were similar in both groups. A significant prolongation in lactate half-life was demonstrated in the cirrhotics (18.8 +/- 1.4 min (mean +/- SEM) compared to 14.7 +/- 2.2 min; P less than 0.02). Since peripheral uptake of lactate in the forearm was similar in the two groups, this suggests that hepatic lactate uptake was impaired, due either to hepatocyte dysfunction or portal diversion.

Adult↗
PubMed1975

Relationship of lactate dehydrogenase specificity and growth rate to lactate metabolism by Selenomonas ruminantium.

A lactate-fermenting strain of Selenomonas ruminantium (HD4) and a lactatenonfermenting strain (GA192) were examined with respect to the stereoisomers of lactate formed during glucose fermentation, the stereoisomers of lactate fermented by HD4, and the characteristics of the lactate dehydrogenases of the strains. GA192 formed L-lactate and HD4 formed L-lactate and small amounts of D-lactate from glucose. HD4 fermended L- but not D-lactate. Both strains contain nicotinamide adenine dinucleotide (NAD)-specific lactate dehydrogenases, and no NAD-independent lactate oxidation was detected. Continuous cultures of both strains grown with limiting glucose produced mainly propionate and acetate and little lactate at dilution rates less than 0.4/h, with shifts to increasing amounts of lactate and less acetate and propionate as the dilution rate was increased from 0.4/h to approximately 1/h.

Acetates↗
PubMed1979

Differences between lactating and non-lactating dairy cows in concentration and secretion rate of insulin.

1. Four parameters of insulin metabolism were compared in catheterized lactating and non-lactating Friesian x Ayrshire dairy cows. 2. The four parameters, i.e. arterial and portal-venous concentrations of insulin, and pancreatic output and hepatic uptake of insulin, were approx. 2-, 3-, 3- and 5-fold higher respectively in the non-lactating cows than in the lactating cows in the normal fed state. Statistical significance was not achieved for the differences in magnitude in the case of the latter two parameters, however. 3. All four parameters increased significantly about 4-fold when non-lactating cows were infused intravenously with glucose for 48 h at a rate of 4.2 mmol/min. The parameters also increased in the lactating cows during glucose infusion, but the values reached were substantially lower than in the non-lactating cows and the increases were not statistically significant. 4. Arterial insulin concentrations doubled in the non-lactating cows during a 3 h infusion of propionate into a mesenteric vein, but remained unaltered in the lactating cows. 5. Differences in insulin concentration and output between the lactating and non-lactating cows were not consistently related to differences in either glucose concentration or glucose-entry rate. Arterial propionate concentrations were similar in both groups of cows at all times. 6. It is concluded that in the dairy cow, insulin secretion in response to an insulinotropic agent is diminished during lactation.

Animals↗
PubMed1992

Is accelerated oxidation of lactate required for dichloroacetate to lower the level of lactate in blood?

We examined mechanisms by which dichloroacetate (DCA), an activator of pyruvate dehydrogenase (PDH), led to a decrease in the concentration of lactate in blood in a unique "metabolic setting," where the concentration of lactate in blood was 5.4 +/- 0.5 mmol/L. Elevated levels of lactate were induced in anaesthetized rabbits by the administration of a large dose of insulin. The rate of consumption of oxygen was 1.2 +/- 0.1 mmol/min, the respiratory quotient was close to unity, and close to half of the PDH was in its active form; therefore, virtually all ATP synthesis should require flux through PDH. Hence, we predicted that DCA should not cause a significant decrease in the concentration of lactate in blood in this model. In contrast, if DCA was effective, new insights could be obtained into its mechanisms of action, at least in this setting. During steady-state hyperlactatemia, DCA was given as its sodium salt, 2 mmol/kg (n = 10); a control group (n = 5) received equimolar NaCl. Forty minutes later, the level of lactate in blood in the DCA group was 1.3 +/- 0.2 mmol/L, significantly lower than in the NaCl group (4.2 +/- 0.6 mmol/L). To determine the organ(s) responsible for removing lactate, arteriovenous differences were measured in organs drained by the jugular, femoral, and hepatic veins. There was no net uptake of lactate in these drainage beds after DCA was administered. From a quantitative analysis of the rate of removal of lactate and the rate of consumption of oxygen, it seems unlikely that the majority of the decrease in lactate could be directly attributed to an increase in its oxidation.

Animals↗
PubMed1977

[Blood picture in lactate acidosis. Part 2: acid-base equilibrium and lactate].

A differentiation between lactate emia (lactic acid emia) and lactate acidosis (lactic acidosis) is made. The normal value for blood lactate concentration is 1-2 mmol/1. The term lactate emia is used for lactate values between 2-6 mmol/1. The limiting value for the diagnosis of lactate acidosis should be more than 7-8 mmol/1 for the blood lactate concentration. Furthermore the different buffer mechanisms are evaluated in respect to their influence on the pH of the blood and to lactate metabolism. Especially the mechanism of respiratory compensation for metabolic acidosis is discussed. It is stated that for the diagnosis of lactate acidosis the blood-pH and the bicarbonate concentration should be measured.

Acid-Base Equilibrium↗
PubMed1992

Localized magnetic resonance spectroscopy measurement of brain lactate during intravenous lactate infusion in healthy volunteers.

Proton magnetic resonance spectroscopy (1H MRS) localized to the left temporal-parietal region in 8 healthy volunteers detected a 2.1-fold +/- 0.7-fold increase (all values +/-SD) in brain lactate during intravenous infusion of 0.5 molar (M) sodium lactate (5 meq/kg over 20 minutes). Significant increases in brain lactate occurred within 5-10 minutes after starting lactate infusion, progressively rose during the infusion, then decreased towards baseline levels during 30 minutes post-infusion. Venous lactate concentration increased from 0.8 +/- 0.2 mM to 10.9 +/- 4.1 mM or 13.6-fold during the infusion. Flow phantom findings in vitro suggest attenuation of 1H MRS blood lactate signal from arteries and veins as a result of flow velocity effects. Correlations between paired blood and brain lactate measurements at each sampling time indicate a non-linear relationship between compartments during lactate infusion.

Adult↗
PubMed1978

Lactate release in relation to tissue lactate in human skeletal muscle during exercise.

In four healthy volunteers, muscle lactate concentration and the release of lactate from the leg were determined at rest and at 4 and 12 min of sitting bicycle exercise at four intensities (30, 50, 70, and 90% of maximal oxygen uptake). The muscle biopsies were obtained by needle biopsy technique from m. vastus lateralis. The rate of lactate release was calculated from the femoral venous-arterial differences of lactate and the leg blood flow was determined by constant rate dye infusion. Both leg blood flow and leg oxygen consumption increased linearly with work intensity. The release of lactate rose approximately linearly with the muscle lactate concentration up to about 4-5 mmol/min but then the relationship revealed a clear leveling off. These results indicate a maximal level for the lactate release from the exercising muscles with a translocation hindrance for lactate within the muscles.

Adult↗
PubMed1977

[Clinical picture of lactate acidosis. 4: Clinical significance of lactate acidosis].

The diagnosis of lactate acidosis is complicated by the fact that lactate determination is not a routine method in clinical chemistry. In fact, lactate analysis is performed only in special laboratories. Even in greater clinics this method is not routinely performed in differential diagnosis of acidotic states. Various diseases are accompanied by a lactate emia or even by lactate acidosis. Anaerobic synthesis of lactate is an emergency reaction to supply minimum energy to tissues with insufficient oxygen supply. The main diseases complicated by increased blood lactate concentrations are shock, circulatory collapse, cardiac failure and peripheral circularoty disturbance. Additionally diabetes mellitus, septical infections, and-the most prominent situation-biguanide intoxications are complicated by an increase in blood lactate concentration.

Acidosis↗
PubMed1976

Changes in lactate dehydrogenase, LDH isoenzymes, lactate, and pyruvate as a result of feeding low fat diets to healthy men and women.

A study was conducted to evaluate the effects on blood lipids and lipoproteins of feeding 21 healthy volunteers, 40-60 yr old, foods commonly eaten in the United States for two 40-day periods. Activities of lactate dehydrogenase (LDH) and LDH isoenzymes, lactate, and pyruvate were monitored. Results showed that LDH activity was significantly lower in all subjects at the end of the 25% fat-calorie period (period I) than at the beginning of the study, but rose above initial levels at the end of the 35% fat-calorie period (period II). While total LDH fell during period I, relative activity of M type subunits of LDH rose significantly in relation to H type in both sexes. This rise is probably indicative of an increase in glycolytic activity as a consequence of the increased intake of dietary carbohydrate. In period I, lactate and pyruvate decreased significantly in males (pyruvate greater than lactate) but not in females. Values for males returned to near initial levels in period II. The ratio of lactate/pyruvate was elevated in both sexes after period I. The greater change in pyruvate relative to lactate with increased dietary carbohydrate suggests increased Krebs Cycle activity. There was a statistically significant positive correlation between lactate, pyruvate, and serum triglyceride for males after they ate the 25% and 35% fat-calorie diets and for females after they ate the 35% fat-calorie diet, but not between lactate, pyruvate, and serum cholesterol for either sex.

Adult↗
PubMed1978

Control of lactate production by Selenomonas ruminantium: homotropic activation of lactate dehydrogenase by pyruvate.

Selenomonas ruminantium produced one mole of D(-)-lactate per mole of glucose used at all dilution rates in ammonia-limited continuous culture. In contrast, lactate production varied according to the dilution rate when glucose was the limiting nutrient. At dilution rates of less than 0.2 h-1, acetate and propionate were the main fermentation products and lactate production was low. At dilution rates above 0.2 h-1, the pattern changed to one of high lactate production similar to that under ammonia limitation. Experiments with cell-free extracts of S. ruminantium showed that D(-)-lactate dehydrogenase had sigmoidal kinetics consistent with homotropic activation of the enzyme by its substrate, pyruvate. This feature allows S. ruminantium to amplify the effects of relatively small changes in the intracellular concentration of pyruvate to cause much larger changes in the rate of production of lactate. Some confirmation that this mechanism of control occurs under physiological conditions was obtained in glucose-limited culture, in which the sigmoidal increase in lactate production was accompanied by a linear increase in pyruvate excretion as the dilution rate increased.

Bacteria↗
PubMed1976

Hormone induced lactation in the cow. IV. Relationships between lactational performance and hormone concentrations in blood plasma.

Concentrations of progesterone, estrogen, and prolactin in plasma were compared among lactations induced in 29 cows by daily subcutaneous injections of .25 mg progesterone and .1 mg estradiol-17beta per kg body weight for 7 days. Superior, median, and inferior lactations were identified by ranking both weightage adjusted maximum milk yields in 7 consecutive days (average 144 +/- 9 kg) and days for milk yield to increase from 5 to 10 kg/day (15 +/- 3 days). Superior and inferior of the former averaged 189 and 101 kg, and their latter averaged 2 and 42 days. Plasma hormones were measured on day 0 before first treatment (day 1), and on days 7, 14, 17, 21, 24, 28, and 35. Superior lactations were associated with below-average progesterone and estrogen in plasma on day 0, rapid decreases in progesterone after day 7 and in estrogen after day 14, and increased prolactin after 7. In comparison, median lactations were associated with elevated progesterone and estrogen after day 17, but prolactin was similar to that of superior lactations. Inferior lactations were associated with decreased prolactin in plasma from days 21 to 35. We hypothesized that (a) first treatment should start 3 to 8 days after estrus, (b) daily doses of estradiol-17beta should be decreased with progesterone unchanged for the 7 days, and (c) estradiol-17beta alone should be continued for 7 days to improve hormonally induced lactations.

Animals↗
PubMed1975

Lactate dehydrogenase isozymes of salmonid fish. Evidence for unique and rapid functional divergence of duplicated H-4 lactate dehydrogenases.

Salmonid fish, as a result of total genome duplication, have two genes, Ldh H and Ldh H', coding for polypeptides H and H', respectively, both of which have been shown in their tetrameric forms to be immunologically related to the classical H-4 lactate dehydrogenase isozyme of higher vertebrates (Bailey, G. S., and Wilson, A. C. (1968) J. Biol. Chem. 243,5843). The H-4 and H'-4 isozymes have now been highly purified from quinnat salmon, and their chemical, physical, immunological, and catalytic properties examined, and compared to the M-4 isozyme of salmon. The two proteins H-4 and H'-4 are shown to be very similar in amino acid composition, but significant differences in a few residues suggest differences in amino acid sequences. This suggestion was born out by quantitative immunological experiments in which the H-4 and H'-4 isozymes were shown to be about as different from each other as are the H-4 lactate dehydrogenases of chicken and duck. This suggests that the gene duplication event in salmon which give rise to two Ldh H genes occurred approximately 80 to 100 million years ago. The H'-4 lactate dehydrogenase which has risen from this duplication in salmon is shown to be somewhat intermediate between H-4 and M-4 in thermal stability, and in all catalytic properties examined, including substrate optima, Michaelis constants, and susceptibility to inhibition by high levels of substrate. In particular the H'-4 isozyme is almost exactly intermediate between H-4 and M-4 in its resistance to product inhibition by lactate, the catalytic parameter suggested to be of major functional importance to M-4 lactate dehydrogenase isozymes (Stambaugh, R., and Post D. (1966) J. Biol. Chem. 241,1462). Further, tissue distribution of these isozymes in salmon and trout are shown to be unusual. The M-4 isozyme salmon and trout are shown to be unusual. The M-4 isozyme occurs in very few tissues in detectable levels. It is the H-4 and H'-4 rather than H-4 and M-4, which occur in independently variable but significant levels in most tissues examined. Thus the H'-4 isozyme, despite its very close structural similarity to H-4 appears to possess functional properties which are different from either H-4 or M-4 in salmon, and some properties are midway between the two. This finding, together with the unusual tissue distribution of these isozymes, suggests that salmon with H'-4 lactate dehydrogenase is evolving to function catalytically in the absence of a balanced H-4-M-4 isozyme complement in most tissues. This balance seems to be met in most tissues by combinations of H-4 and H'-4,

Amino Acids↗
PubMed1976

Spectrophotometric and electrochemical determinations of L(+)-lactate in blood by use of lactate dehydrogenase from yeast.

Lactate can be determined rapidly in blood by spectrophotometric and amperometric (enzyme electrode) procedures based on its oxidation by ferricyanide, the reaction being catalyzed with yeast L(+)-lactate dehydrogenase (cytochrome b2) (EC 1.1.2.3). In the photometric method lactate can be measured in a few minutes, but blood samples must first be deproteinized. In the amperometric procedure no treatment of blood is needed except ferricyanide addition. The enzyme electrode we used has a response time shorter than 1 min when its critical variables are optimized. Preliminary standardization is reduced to minimum operation, because electrode response is proportional to lactate concentration over a wide range (0.1 to 8.0 mol/liter) and many determinations can be done with little cost in enzyme. A simple electrical device ("two-electrode device") is described that is well suited for furture micro-cell construction. Lactate determinations on a series of normal blood samples show no deviation between results by these new methods and the usual ultraviolet spectrophotometric lactate tests.

Animals↗