scholarly journals Measurements of the turnover rate of glutamine in normal and acidotic rats

1983 ◽  
Vol 210 (1) ◽  
pp. 277-280 ◽  
Author(s):  
E J Squires ◽  
J T Brosnan
Keyword(s):  
Metabolic Acidosis ◽  
Turnover Rate ◽  
Whole Body ◽  
Constant Infusion ◽  
Chronic Metabolic Acidosis

The turnover of glutamine was measured in rats with [1-14C]glutamine. Rates of turnover measured by constant infusion of the label were 130 mumol/h per 100g body wt. in control rats and were not changed in chronic metabolic acidosis. These rates of turnover of whole-body glutamine were about 13-26% of the rate of net glutamine release into the bloodstream, indicating that the bulk of glutamine turnover in vivo is concerned with intracellular processes rather than inter-organ fluxes.

scholarly journals Comparison of different techniques for estimating rates of protein synthesis in vivo in healthy and bacteraemic rats

1985 ◽  
Vol 226 (1) ◽  
pp. 37-42 ◽  
Author(s):  
J J Pomposelli ◽  
J D Palombo ◽  
K J Hamawy ◽  
B R Bistrian ◽  
G L Blackburn ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Rectus Muscle ◽  
Stochastic Modelling ◽  
Whole Body ◽  
Constant Infusion ◽  
Second Phase ◽  
Sprague Dawley ◽  
Body Protein ◽  
To Receive

Previous studies have reported that use of a flooding dose of radiolabelled amino acid is a more precise technique than the constant infusion of tracer quantities for determining rates of protein synthesis in rapidly turning-over tissues in the rat. However, there has been little direct investigation comparing different methods under comparable conditions. Initially, 12 healthy male Sprague-Dawley rats, weighing approx. 100 g, were randomized to receive either a bolus intravenous injection of 100 mumol of L-leucine (containing 30 microCi of [1-14C]leucine)/100 g body wt., or a continuous 2 h tracer infusion of [14C]leucine. In the second phase of the experiment, 12 additional rats were intravenously injected with 1 × 10(8) colony-forming units of Pseudomonas aeruginosa and 16 h later randomized to receive one of two infusions described above. Total protein synthesis as well as fractional synthesis rates were determined in liver, rectus muscle and whole body. Synthesis rates measured in liver, muscle and whole body were significantly higher in bacteraemic rats than in healthy rats. The flooding-dose methodology gave significantly higher estimates of protein synthesis in the liver, skeletal muscle and whole body than did the continuous-infusion method using direct measurement of the acid-soluble fraction from the respective tissue. Indirect estimates of whole-body protein synthesis based on plasma enrichments and stochastic modelling gave the lowest values.

Compartmental model of leucine kinetics in humans

1991 ◽  
Vol 261 (4) ◽  
pp. E539-E550 ◽  
Author(s):  
C. Cobelli ◽  
M. P. Saccomani ◽  
P. Tessari ◽  
G. Biolo ◽  
L. Luzi ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Compartmental Model ◽  
Linear Time ◽  
A Priori ◽  
Normal Subjects ◽  
Whole Body ◽  
Constant Infusion ◽  
Individual Subject ◽  
Domain Of Validity

The complexity of amino acid and protein metabolism has limited the development of comprehensive, accurate whole body kinetic models. For leucine, simplified approaches are in use to measure in vivo leucine fluxes, but their domain of validity is uncertain. We propose here a comprehensive compartmental model of the kinetics of leucine and alpha-ketoisocaproate (KIC) in humans. Data from a multiple-tracer administration were generated with a two-stage (I and II) experiment. Six normal subjects were studied. In experiment I, labeled leucine and KIC were simultaneously injected into plasma. Four plasma leucine and KIC tracer concentration curves and label in the expired CO2 were measured. In experiment II, labeled bicarbonate was injected into plasma, and labeled CO2 in the expired air was measured. Radioactive (L-[1-14C]leucine, [4,5-3H]KIC, [14C]bicarbonate) and stable isotope (L-[1-13C]leucine, [5,5,5-2H3]KIC, [13C]bicarbonate) tracers were employed. The input format was a bolus (impulse) dose in the radioactive case and a constant infusion in the stable isotope case. A number of physiologically based, linear time-invariant compartmental models were proposed and tested against the data. The model finally chosen for leucine-KIC kinetics has 10 compartments: 4 for leucine, 3 for KIC, and 3 for bicarbonate. The model is a priori uniquely identifiable, and its parameters were estimated with precision from the five curves of experiment I. The separate assessment of bicarbonate kinetics (experiment II) was shown to be unnecessary. The model defines masses and fluxes of leucine in the organism, in particular its intracellular appearance from protein breakdown, its oxidation, and its incorporation into proteins. An important feature of the model is its ability to estimate leucine oxidation by resolving the bicarbonate model in each individual subject. Finally, the model allows the assessment of the domain of validity of the simpler commonly used models.

scholarly journals The kidney of chicken adapts to chronic metabolic acidosis: In vivo and in vitro studies

1982 ◽  
Vol 22 (2) ◽  
pp. 103-111 ◽  
Author(s):  
André G. Craan ◽  
◽  
Guy Lemieux ◽  
Patrick Vinay ◽  
André Gougoux
Keyword(s):  
Metabolic Acidosis ◽  
In Vitro Studies ◽  
Chronic Metabolic Acidosis

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.

scholarly journals A Kinetic Method for the Measurement of Zinc Influx In Vivo in the Rainbow Trout, and the Effects of Waterborne Calcium on Flux Rates

1989 ◽  
Vol 142 (1) ◽  
pp. 425-446 ◽  
Author(s):  
D. J. SPRY ◽  
C. M. WOOD
Keyword(s):  
Rainbow Trout ◽  
Plasma Sample ◽  
Kinetic Method ◽  
Whole Body ◽  
Constant Infusion ◽  
Linear Component ◽  
Experimental Apparatus ◽  
Body Counting ◽  
Whole Body Counting

Three methods were evaluated to measure rate of influx of Zn into rainbow trout. The first two, disappearance of 65Zn from the water and whole-body counting, overestimated influx when compared with a third method which used a terminal plasma sample to calculate influx. The cause of the overestimate was a short-term adsorption phenomenon to both the experimental apparatus and the exterior of the fish. The third method measured only Zn which entered the fish. This method entailed ‘calibration’ of cannulated trout by constant infusion of small amounts of radiolabelled Zn. This was analogous to the entry of Zn into fish across the gill. After 24–36 h of infusion, plasma radioactivity reached a steadystate concentration which was a simple linear function of the rate of infusion. This relationship was then used to predict influx from a single terminal plasma sample from uncannulated trout exposed to radiolabelled Zn in the water. Trout acclimated to tapwater (Ca2+ = 2.0 mequivl−1) and exposed to Zn (1.5-45.9 μequivl−1; 0.05-1.5 mgl−1) showed saturable uptake which was apparently first order with no significant linear component. The apparent Jmax and Km were 314 nequiv kg−1 h−1 and 7.3 μequivl−1 (0.24 mgl−1), respectively. Acutely raising the waterborne [Ca2+] (4.7 and 9.7 mequivl−1) over the same range of [Zn] revealed a competitive type of interaction - little change in Jmax, with increased Km. When Ca2+ was acutely removed (0.05 and 1.02 mequivl−1) by the use of artificial soft water, significant linear influx occurred in addition to the saturable uptake noted at higher [Ca2+], suggesting the opening of a paracellular leak. Calculation of the inhibitor constant for Ca2+ yielded a value of 0.48 mequivl−1. This value is similar to the Km for Ca2+ when it was a transported substrate (0.28 ± 0.07 mequivl−1). The true Km for Zn transport in the absence of Ca2+ was 1.0 μequivl−1 (0.06 mgl−1). These data showed Zn influx to be saturable and strongly dependent upon waterborne [Ca2+], perhaps traversing the gill in a manner similar to Ca2+.

Intracellular bicarbonate of skeletal muscle under different metabolic states

1976 ◽  
Vol 230 (1) ◽  
pp. 228-232 ◽  
Author(s):  
RN Khuri ◽  
SK Agulian ◽  
KK Bogharian
Keyword(s):  
Metabolic Acidosis ◽  
Intracellular Ph ◽  
Metabolic Alkalosis ◽  
Equilibrium Potential ◽  
Chronic Metabolic Acidosis ◽  
Cell Ph ◽  
Metabolic States ◽  
Na Depletion ◽  
K Depletion

Intracellular bicarbonate of single muscle fibers in vivo was measured by a direct electrometric method simultaneously with the membrane PD in rats under seven different metabolic states. From the measured intracellular bicarbonate values and the PCO2, the bicarbonate equilibrium potential and the intracellular pH were calculated. The mean intracellular [HCO3-] under normal control conditions was 10.3 +/- 0.7 mM (SE). The intracellular bicarbonate fell significantly in both chronic metabolic acidosis and chronic K+ depletion. In contrast, intracellular bicarbonate was elevated in chronic metabolic alkalosis, K+ loading, and Na+ depletion. Taking intracellular pH as an index of the acid-base status of cells, we find that whereas the calculated cell pH decreased along with the cell bicarbonate in both chronic metabolic acidosis and K+ depletion, cell pH increased along with the bicarbonate only in chronic metabolic alkalosis. Cell pH was unchanged in both chronic K+ loading and Na+ depletion.

31P-NMR in vivo measurement of renal intracellular pH: effects of acidosis and K+ depletion in rats

1986 ◽  
Vol 251 (5) ◽  
pp. F904-F910 ◽  
Author(s):  
W. R. Adam ◽  
A. P. Koretsky ◽  
M. W. Weiner
Keyword(s):  
Metabolic Acidosis ◽  
Intracellular Ph ◽  
Respiratory Acidosis ◽  
Resonance Spectroscopy ◽  
Ph Effects ◽  
Potassium Depletion ◽  
Chronic Metabolic Acidosis ◽  
Arterial Blood ◽  
Blood Ph

Renal intracellular pH (pHi) was measured in vivo from the chemical shift (sigma) of inorganic phosphate (Pi), obtained by 31P-nuclear magnetic resonance spectroscopy (NMR). pH was calculated from the difference between sigma Pi and sigma alpha-ATP. Changes of sigma Pi closely correlated with changes of sigma monophosphoesters; this supports the hypothesis that the pH determined from sigma Pi represents pHi. Renal pH in control rats was 7.39 +/- 0.04 (n = 8). This is higher than pHi of muscle and brain in vivo, suggesting that renal Na-H antiporter activity raises renal pHi. To examine the relationship between renal pH and ammoniagenesis, rats were subjected to acute (less than 24 h) and chronic (4-7 days) metabolic acidosis, acute (20 min) and chronic (6-8 days) respiratory acidosis, and dietary potassium depletion (7-21 days). Acute metabolic and respiratory acidosis produced acidification of renal pHi. Chronic metabolic acidosis (arterial blood pH, 7.26 +/- 0.02) lowered renal pHi to 7.30 +/- 0.02, but chronic respiratory acidosis (arterial blood pH, 7.30 +/- 0.05) was not associated with renal acidosis (pH, 7.40 +/- 0.04). At a similar level of blood pH, pHi was higher in chronic metabolic acidosis than in acute metabolic acidosis, suggesting an adaptive process that raises pHi. Potassium depletion (arterial blood pH, 7.44 +/- 0.05) was associated with a marked renal acidosis (renal pH, 7.17 +/- 0.02). There was a direct relationship between renal pH and cardiac K+. Rapid partial repletion with KCl (1 mmol) significantly increased renal pHi from 7.14 +/- 0.03 to 7.31 +/- 0.01.(ABSTRACT TRUNCATED AT 250 WORDS)

A quantitative analysis of renal ammoniagenesis and energy balance: a theoretical approach

1982 ◽  
Vol 60 (12) ◽  
pp. 1431-1435 ◽  
Author(s):  
Mitchell L. Halperin ◽  
Robert L. Jungas ◽  
Carole Pichette ◽  
Marc B. Goldstein
Keyword(s):  
Metabolic Acidosis ◽  
Quantitative Analysis ◽  
Maximum Rate ◽  
Intact Animal ◽  
Maximum Velocity ◽  
Chronic Metabolic Acidosis ◽  
Atp Production ◽  
Ammonium Production ◽  
Substrate Concentrations

Many theories have been proposed to explain the regulation of renal ammoniagenesis during chronic metabolic acidosis but none of these is entirely satisfactory. Since the activity of each of the enzymes in this pathway greatly exceeds the maximum rate of ammonium production in vivo, even when physiological substrate concentrations are used in this calculation, it follows that ammoniagenesis must be inhibited in the intact animal. We shall present a novel hypothesis for the regulation of the maximum rate of ammoniagenesis which emphasizes the fact that ATP is a product of this pathway and that a limited rate of ATP utilization could control its maximum velocity during chronic metabolic acidosis. To test the validity of our hypothesis, a quantitative analysis of the pathways of ATP production and utilization in the kidney will be reviewed. This approach is similar to one already proposed for the regulation of the maximum rate of ketogenesis in the liver.

Measuring whole-body actin/myosin protein breakdown in mice using a primed constant stable isotope-infusion protocol

2003 ◽  
Vol 104 (6) ◽  
pp. 585-590 ◽  
Author(s):  
Yvonne L. J. VISSERS ◽  
Maarten F. VON MEYENFELDT ◽  
Valeria B. BRAULIO ◽  
Yvette C. LUIKING ◽  
Nicolaas E. P. DEUTZ
Keyword(s):  
Stable Isotope ◽  
Total Protein ◽  
Myofibrillar Protein ◽  
Whole Body ◽  
Constant Infusion ◽  
Protein Breakdown ◽  
Net Protein ◽  
Infusion Protocol

To measure actin/myosin protein breakdown, the 24 h excretion of Nτ-methylhistidine (3MH) is used. However, in mice, this method is invalid. Therefore we have developed a liquid chromatography-MS technique to measure the tracer/tracee ratio and concentration of 3MH in plasma, enabling an in vivo primed constant infusion protocol with a deuterated stable isotope of 3MH. We tested this model by giving a primed constant infusion of L-[3-methyl-2H3]histidine, L-[phenyl-2H5]phenylalanine and L-[phenyl-2H2]tyrosine to three anaesthetized experimental groups: mice receiving saline intraperitoneally (i.p.) (CON), mice receiving saline i.p. and starved for 9 h (STA), and mice receiving lipopolysaccharide i.p. and starved for 9 h (STA + LPS). The contribution of myofibrillar to total protein breakdown was significantly lower in the STA group than the CON group (30±4% and 54±14% respectively; P<0.05), and was significantly higher in the STA + LPS group than the STA group (52±7% and 30±4% respectively; P<0.05). Whole-body myofibrillar protein breakdown, total protein breakdown, protein synthesis and net protein breakdown were not different between the groups. We conclude that this in vivo primed constant stable isotope-infusion protocol can give valuable information about the role of actin/myosin protein breakdown in mice.

Effect of chronic metabolic acidosis on bone density and bone architecture in vivo in rats

2014 ◽  
Vol 306 (5) ◽  
pp. F517-F524 ◽  
Author(s):  
Jürg A. Gasser ◽  
Henry N. Hulter ◽  
Peter Imboden ◽  
Reto Krapf
Keyword(s):  
Metabolic Acidosis ◽  
Bone Resorption ◽  
Bone Mass ◽  
Cortical Bone ◽  
Bone Microarchitecture ◽  
Chronic Metabolic Acidosis ◽  
Ovx Rats ◽  
Cortical Bone Mass ◽  
Trabecular Number

Chronic metabolic acidosis (CMA) might result in a decrease in vivo in bone mass based on its reported in vitro inhibition of bone mineralization, bone formation, or stimulation of bone resorption, but such data, in the absence of other disorders, have not been reported. CMA also results in negative nitrogen balance, which might decrease skeletal muscle mass. This study analyzed the net in vivo effects of CMA's cellular and physicochemical processes on bone turnover, trabecular and cortical bone density, and bone microarchitecture using both peripheral quantitative computed tomography and μCT. CMA induced by NH4Cl administration (15 mEq/kg body wt/day) in intact and ovariectomized (OVX) rats resulted in stable CMA (mean Δ[HCO3−]p = 10 mmol/l). CMA decreased plasma osteocalcin and increased TRAP5b in intact and OVX animals. CMA decreased total volumetric bone mineral density (vBMD) after 6 and 10 wk ( week 10: intact normal +2.1 ± 0.9% vs. intact acidosis −3.6 ± 1.2%, P < 0.001), an effect attributable to a decrease in cortical thickness and, thus, cortical bone mass (no significant effect on cancellous vBMD, week 10) attributed to an increase in endosteal bone resorption (nominally increased endosteal circumference). Trabecular bone volume (BV/TV) decreased significantly in both CMA groups at 6 and 10 wk, associated with a decrease in trabecular number. CMA significantly decreased muscle cross-sectional area in the proximal hindlimb at 6 and 10 wk. In conclusion, chronic metabolic acidosis induces a large decrease in cortical bone mass (a prime determinant of bone fragility) in intact and OVX rats and impairs bone microarchitecture characterized by a decrease in trabecular number.

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