scholarly journals The determination of lactate turnover in vivo with 3H- and 14C-labelled lactate. The significance of sites of tracer administration and sampling

1981 ◽  
Vol 194 (2) ◽  
pp. 513-524 ◽  
Author(s):  
J Katz ◽  
F Okajima ◽  
M Chenoweth ◽  
A Dunn
Keyword(s):  
Specific Radioactivity ◽  
Vena Cava ◽  
Turnover Rates ◽  
High Turnover ◽  
Glucose Carbon ◽  
Lactate Turnover ◽  
Carbon Recycling ◽  
Kinetics Of

L-[3-3H,U-14C]Lactate was administered to starved rats either as a bolus or by continuous infusion. Tracer administration was performed two ways: injection into the vena cava and sampling from the aorta (V-A mode), or injection into the aorta and sampling from the vena cava (A-VC mode). The specific-radioactivity curves after infusion or injection differed markedly with the two procedures. However, the specific radioactivities of 14C-labelled glucose derived from [U-14C]lactate were similar in the two modes. The apparent turnover rates of lactate calculated from the 3H specific-radioactivity curves in the V-A mode were about half those obtained from the 3H specific-radioactivity curves in the A-VC mode. The apparent contribution of lactate carbon to glucose carbon calculated from specific-radioactivity curves of the A-VC mode was greater than that obtained from the V-A mode. The apparent recycling of lactate carbon calculated from the specific radioactivities for [U-14C]- and [3-3H]-lactate was greater in the A-VC mode than the V-A mode. [U-14C] Glucose was administered in the two modes, but in contrast with lactate the specific radioactivities were only slightly different. An analysis to account for these observations is presented. It is shown that the two modes represent sampling from different pools of lactate. The significance of sites of tracer administration and sampling for the interpretation of tracer kinetics of compounds present in intracellular and extracellular spaces, and with a high turnover rate, is discussed. We propose that for such compounds, including lactate, alanine and glycerol, the widely used V-A mode leads to a marked underestimate of replacement, mass and carbon recycling, and that the A-VC mode is the preferred method for the assessment of these parameters.

Determination of gluconeogenesis in vivo with 14C-labeled substrates

1985 ◽  
Vol 248 (4) ◽  
pp. R391-R399 ◽  
Author(s):  
J. Katz
Keyword(s):  
Pyruvate Carboxylase ◽  
Tricarboxylic Acid Cycle ◽  
Specific Radioactivity ◽  
Tricarboxylic Acid ◽  
Pyruvate Metabolism ◽  
Acetyl Coenzyme A ◽  
Glucose Carbon ◽  
Labeling Pattern

A mitochondrial model of gluconeogenesis and the tricarboxylic acid cycle, where pyruvate is metabolized via pyruvate carboxylase and pyruvate dehydrogenase, and pyruvate kinase is examined. The effect of the rate of tricarboxylic acid flux and the rates of the three reactions of pyruvate metabolism on the labeling patterns from [14C]pyruvate and [24C]acetate are analyzed. Expressions describing the specific radioactivities and 14C distribution in glucose as a function of these rates are derived. Specific radioactivities and isotopic patterns depend markedly on the ratio of the rates of pyruvate carboxylation and decarboxylation to the rate of citrate synthesis, but the effect of phosphoenolpyruvate hydrolysis is minor. The effects of these rates on 1) specific radioactivity of phosphoenolpyruvate, 2) labeling pattern in glucose, and 3) contribution of pyruvate, acetyl-coenzyme A, and CO2 to glucose carbon are illustrated. To determine the contribution of lactate or alanine to gluconeogenesis, experiments with two compounds labeled in different carbons are required. Methods in current use to correct for the dilution of 14C in gluconeogenesis from [14C]pyruvate are shown to be erroneous. The experimental design and techniques to determine gluconeogenesis from 14C-labeled precursors are presented and illustrated with numerical examples.

scholarly journals Determination of synthesis, recycling and body mass of glucose in rats and rabbits in vivo with 3H- and 14C-labelled glucose

1974 ◽  
Vol 142 (1) ◽  
pp. 171-183 ◽  
Author(s):  
Joseph Katz ◽  
Arnold Dunn ◽  
Maymie Chenoweth ◽  
Sybil Golden
Keyword(s):  
Body Mass ◽  
Plasma Glucose ◽  
Specific Radioactivity ◽  
Total Body Mass ◽  
Glucose Carbon ◽  
Multicompartmental Model ◽  
Glucose Synthesis ◽  
Total Body

1. Glucose labelled with 3H in position 2 and uniformly with 14C was administered simultaneously to rabbits and rats either as a single injection or by continuous infusion. Plasma glucose specific radioactivity and the yield of 3H in the plasma water were monitored. 2. The rates of synthesis, recycling of carbon and total body mass of glucose were calculated, without assuming a multicompartmental model and without fitting data by exponential expressions. 3. The rate of synthesis of glucose in starved-overnight rabbits was 4mg/min per kg (range 3–4.5mg/min per kg) and 25–35% of the glucose carbon was recycled. The mass of total body glucose in starved rabbits was 290mg/kg (range 220–390mg/kg). About one-third of the total body glucose equilibrates nearly instantaneously with plasma glucose. 4. In rats starved overnight, glucose synthesis was about 10mg/min per kg and recycling of carbon ranged from 30–40%. Total body mass (per kg body weight) is similar to that in rabbits. 5. The activity in plasma water after injection of [2-3H]glucose was determined. The initial rate of 3H2O formation is rapid, indicating that the major site of glucose catabolism is in the rapidly mixing pool. The curve of total body glucose radioactivity was obtained from the 3H2O yield, and total mass of glucose was calculated. This agrees with that obtained from the 3H specific-radioactivity curve.

scholarly journals FSMP-06. IN VIVO MONITORING OF LDHA EXPRESSION IN GLIOBLASTOMA USING QUANTITATIVE EXCHANGED-LABEL TURNOVER 1H MRS TECHNIQUE

2020 ◽  
Vol 3 (Supplement_1) ◽  
pp. i17-i17
Author(s):  
Puneet Bagga ◽  
Laurie Rich ◽  
Mohammad Haris ◽  
Neil Wilson ◽  
Mitch Schnall ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Lactate Production ◽  
Deuterium Labeling ◽  
1H Mrs ◽  
In Vivo Monitoring ◽  
Lactate Turnover ◽  
Crucial Information ◽  
Specialized Hardware

Abstract Most cancers, including glioblastomas (GBMs), rely extensively on glycolysis to support growth, proliferation, and survival. A hallmark of this elevated glycolysis is overexpression of Lactate dehydrogenase-A (LDHA) protein leading to increased uptake of glucose and overproduction of lactate. Various clinical trials using LDHA as a target for diagnosis and treatment have yielded encouraging results. However, in vivo monitoring of LDHA expression has been challenging due to either requirement of administration of radioactive substrates or specialized hardware. In this presentation, we will demonstrate a new method-quantitative exchanged-label turnover MRS (QELT, or simply qMRS)-that increases the sensitivity of magnetic resonance-based metabolic mapping without the requirement for specialized hardware. qMRS relies on the administration of deuterated (2H-labeled) substrates to track the production of downstream metabolites. Since 2H is invisible on 1H MRS, replacement of 1H with 2H due to metabolic turnover leads to an overall reduction in 1H MRS signal for the corresponding metabolites. We applied our qMRS technique to monitor the rate of lactate production in a preclinical GBM model. Infusion of [6,6’-2H2]glucose led to downstream deuterium labeling of lactate, thereby resulting in a reduction in the 1.33 ppm lactate-CH3 peak on 1H MRS over time. The subtraction of post-administration 1H MR spectra from the pre-infusion spectra aided in the determination of the kinetics of the lactate turnover. We believe that the detection and quantification of lactate production kinetics may provide crucial information regarding tumor LDHA expression non-invasively in GBMs without requiring biopsies. Hence, qMRS is expected to open up new opportunities to probe LDHA expression differences in a variety of gliomas, including GBMs and astrocytomas. This method takes advantage of the universal availability and ease of implementation of 1H MRS on all clinical and preclinical magnetic resonance scanners.

scholarly journals Determination of the steady-state turnover rates of the metabolically active pools of phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate in human erythrocytes

1989 ◽  
Vol 259 (3) ◽  
pp. 893-896 ◽  
Author(s):  
C E King ◽  
P T Hawkins ◽  
L R Stephens ◽  
R H Michell
Keyword(s):  
Steady State ◽  
Rate Constants ◽  
Human Erythrocytes ◽  
Turnover Rates ◽  
Metabolic Fluxes ◽  
Metabolic Pool ◽  
Phosphatidylinositol 4 ◽  
Kinetics Of ◽  
Phosphate Groups

When intact human erythrocytes are incubated at metabolic steady state in a chloride-free medium containing [32P]Pi, there is rapid labelling of the gamma-phosphate of ATP, followed by a slower labelling of the monoester phosphate groups of phosphatidylinositol 4-phosphate (PtdIns4P) and phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] [King, Stephens, Hawkins, Guy & Michell (1987) Biochem. J. 244, 209-217]. We have analysed the early kinetics of the labelling of these phosphate groups, in order to determine: (a) the steady-state rates of the interconversions of phosphatidylinositol, PtdIns4P and PtdIns(4,5)P2; and (b) the fractions of the total cellular complement of PtdIns4P and PtdIns(4,5)P2 that participate in this steady-state turnover. The experimental data most closely fit a pattern of PtdIns4P and PtdIns(4,5)P2 turnover in which one-quarter of the total cellular complement of each lipid is in the metabolic pool that participates in rapid metabolic turnover, with rate constants of 0.028 min-1 for the interconversion of PtdIns and PtdIns4P, and of 0.010 min-1 for the PtdIns4P/PtdIns(4,5)P2 cycle. These rate constants represent metabolic fluxes of approx. 2.1 nmol of lipid/h per ml of packed erythrocytes between PtdIns and PtdIns4P and of approx. 5.7 nmol/h per ml of cells between PtdIns4P and PtdIns(4,5)P2.

Measurement of leucine metabolism in man from a primed, continuous infusion of L-[1-3C]leucine

1980 ◽  
Vol 238 (5) ◽  
pp. E473-E479 ◽  
Author(s):  
D. E. Matthews ◽  
K. J. Motil ◽  
D. K. Rohrbaugh ◽  
J. F. Burke ◽  
V. R. Young ◽  
...  
Keyword(s):  
Steady State ◽  
Continuous Infusion ◽  
Co2 Production ◽  
Human Beings ◽  
Priming Dose ◽  
Leucine Metabolism ◽  
Kinetics Of ◽  
13Co2 Enrichment

Leucine metabolism in vivo can be determined from a primed, continuous infusion of L-[1-13C]leucine by measuring, at isotopic steady state, plasm [-13C]leucine enrichment, expired 13CO2 enrichment, and CO2 production rate. With an appropriate priming dose of L-[1-13C]leucine and NaH13CO3, isotopic steady state is reached in less than 2 h, and the infusion is completed in 4 h. The method can determine rates of leucine turnover, oxidation, and incorporation into protein with typical relative uncertainties of 2, 10, and 4%, respectively. The method requires no more than 1 ml of blood and uses stable isotope rather than radioisotope techniques. Thus, the method is applicable to studies of human beings of all ages. L-[1-13C]leucine may be infused with a second amino acid labeled with 15N for simultaneous determination of the kinetics of two amino acids.

scholarly journals Measurement of protein turnover in rat liver. Analysis of the complex curve for decay of label in a mixture of proteins

1976 ◽  
Vol 156 (3) ◽  
pp. 657-663 ◽  
Author(s):  
P J Garlick ◽  
J C Waterlow ◽  
R W Swick
Keyword(s):  
Rat Liver ◽  
Turnover Rate ◽  
Decay Curve ◽  
Specific Radioactivity ◽  
Liver Protein ◽  
Turnover Rates ◽  
A Value ◽  
Maximum Value ◽  
Single Exponential

The curve for decay of 14C in rat liver protein labelled by injection of NaH14CO3 was analysed to obtain the average turnover rate of mixed liver protein. Three different methods of analysis were used. (1) Unlike decay curves from homogeneous proteins, the curve did not fit a single exponential, but a good fit was obtained with three exponentials. By assuming that the mixture contained three major components with different turnover rates, the calculated value for the average turnover rate (k) was close to 40% per day. (2) k was also calculated from the area under the decay curve, a method which makes no assumptions about the number of proteins in the mixture. This method also gave a value close to 40% per day. (3) It was shown empirically, both by simulation of decay of label in model mixtures of protein and with the decay curve measured in vivo, that k can be calculated from the time taken for the specific radioactivity to fall to 10% of its maximum value. This is an advantage, since the other two methods require the decay curve to be measured over a much longer period of time.

scholarly journals Lactate metabolism in the perfused rat hindlimb

1984 ◽  
Vol 222 (2) ◽  
pp. 281-292 ◽  
Author(s):  
M Shiota ◽  
S Golden ◽  
J Katz
Keyword(s):  
Glycogen Synthesis ◽  
Lactate Concentration ◽  
Specific Radioactivity ◽  
Bicarbonate Buffer ◽  
Glucose Carbon ◽  
Lactate Turnover ◽  
Net Uptake ◽  
Lactate Uptake ◽  
Glycogen Deposition ◽  
Fast Twitch

A preparation of isolated rat hindleg was perfused with a medium consisting of bicarbonate buffer containing Ficoll and fluorocarbon, containing glucose and/or lactate. The leg was electrically prestimulated to deplete partially muscle glycogen. The glucose was labelled uniformly with 14C and with 3H in positions 2, 5 or 6, and lactate uniformly with 14C and with 3H in positions 2 or 3. Glucose carbon was predominantly recovered in glycogen, and to a lesser extent in lactate. The 3H/14C ration in glycogen from [5-3H,U-14C]- and [6-3H,U-14C]-glucose was the same as in glucose. Nearly all the utilized 3H from [2-3H]glucose was recovered as water. Insulin increased glucose uptake and glycogen synthesis 3-fold. When the muscle was perfused with a medium containing 10 mM-glucose and 2 mM-lactate, there was little change in lactate concentration. 14C from lactate was incorporated into glycogen. There was a marked exponential decrease in lactate specific radioactivity, much greater with [3H]- than with [14C]-lactate. The ‘apparent turnover’ of [U-14C]lactate was 0.28 mumol/min per g of muscle, and those of [2-3H]- and [3-3H]-lactate were both about 0.7 mumol/min per g. With 10 mM-lactate as sole substrate, there was a net uptake of lactate, at a rate of about 0.15 mumol/min per g, and the apparent turnover of [U-14C]lactate was 0.3 mumol/min per g. The apparent turnover of [3H]lactate was 3-5 times greater. When glycogen synthesis was low (no prestimulation, no insulin), the incorporation of lactate carbon into glycogen exceeded that from glucose, but at high rates of glycogen deposition the incorporation of lactate carbon was much less than that of glucose. Lactate incorporation into glycogen was similar in fast-twitch white and fast-twitch red muscle, but was very low in slow-twitch red fibres. We find that (a) pyruvate in muscle is incorporated into glycogen without randomization of carbon, and synthesis is not inhibited by mercaptopicolinate or cycloserine; (b) there is extensive lactate turnover in the absence of net lactate uptake, and there is a large dilution of 14C-labelled lactate from endogenous supply; (c) there is extensive detritiation of [2-3H]- and [3-3H]-lactate in excess of 14C utilization.

scholarly journals In vivo threonine oxidation in growing pigs fed on diets with graded levels of threonine

1996 ◽  
Vol 75 (6) ◽  
pp. 825-837 ◽  
Author(s):  
N. Le Floc'h ◽  
C. Obled ◽  
B. Sève
Keyword(s):  
Specific Radioactivity ◽  
Vena Cava ◽  
Live Weight ◽  
Growing Pigs ◽  
Whole Body ◽  
Constant Infusion ◽  
Balanced Diet ◽  
Liver And Pancreas ◽  
Venous Plasma

Threonine oxidation to glycine was investigated in vivo in twelve growing pigs (27·4 kg live weight) fed on one of the following three diets with graded levels of threonine supply: a low-threonine diet (LT), a control well-balanced diet (C) or a high-threonine diet (HT), during 10h constant infusion of L-[1-13C]threonine and [2-3H]glycine in the cranial vena cava and [l-14C]glycine in the portal vein.13C-threonine and glycine enrichments and [3H]glycine and [14C]glycine specific radioactivities (SR) were determined at plateau in peripheral venous plasma, liver and pancreas. Glycine praduction rates calculated from plasma [2-3H]glycine or [1-14C]glycine SR gave similar values suggesting that [l-14C]glycine SR could be used in order to estimate whole-body glycine flux. The high pancreas [1-13C]glycine enrichment provided evidence that the pancreas may be, with the liver, a major site of threonine oxidation to glycine. Moreover, the present findings suggest that threonine transport into the Liver could be the limiting step of threonine oxidation in this tissue when dietary threonine supply is low. Total threonine oxidation to glycine, calculated from plasma values of enrichment and specific radioactivity, was low and constant when the estimated absorbed threonine was lower than 4 g/d and increased for higher amounts of absorbed threonine.

On the determination of turnover in vivo with tracers

1992 ◽  
Vol 263 (3) ◽  
pp. E417-E424
Author(s):  
J. Katz
Keyword(s):  
Specific Activity ◽  
Venous Blood ◽  
Vena Cava ◽  
Whole Body ◽  
Mixed Venous Blood ◽  
Close Approximation ◽  
High Turnover ◽  
The Right ◽  
Mixed Venous

Theoretical and practical aspects of the application of tracer methods for the measurement of turnover of blood-borne compounds are discussed, with special regard to lactate. The validity of the application of the tracer into the aortic arch and sampling from the right atrium (A-V), the administration of tracer into the vena cava and sampling from the aorta (V-A), and sampling to the determination of turnover are examined, using numerical examples. It is shown that the difference between specific activity in arterial and mixed venous blood depends mainly on the cardiac output, the ratio of tracee turnover to the mass of circulating tracee, and the sites of production and utilization of the tracee. Conditions are shown under which the A-V and V-A modes overestimate or underestimate the true rate of turnover. In theory, the A-V mode provides an exact estimate of turnover when the mean specific activity of the tracee in the whole body equals the specific activity of mixed venous blood in the right heart. It is shown that, for compounds with a high turnover rate, the underestimate in the A-V mode is small, and the mode provides a close approximation of true turnover. The underestimate in the V-A mode at high turnover rates is extensive. Experimental evidence indicates that, in several animal species, the specific activity of lactate and several amino acids in several organs and tissues nearly equals that in the venous blood, with the A-V mode providing a close approximation of the true turnover for these compounds.(ABSTRACT TRUNCATED AT 250 WORDS)

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