GC-MS determination of ratios of stable-isotope labelled to natural urea using [13C15N2]urea for studying urea kinetics in serum and as a means to validate routine methods for the quantitative assay of urea in dialysate

Wolthers, B.G.; Tepper, T.; Withag, A.; Nagel, G.T.; Haan, T. H. Y. De; Leeuwen, J.J.van; Stegeman, Coen A.; Huisman, Roel M.

doi:10.1016/0009-8981(94)90025-6

Cited by 11 publications

(3 citation statements)

References 7 publications

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“…Plasma urea enrichment was determined by GC±combus-tion±isotope ratio mass spectrometry (GC±C±IRMS). In order to improve the GC separation, urea was ®rst converted to 2-hydroxypyrimidine (Wolthers et al 1994). Samples were dried in v-vials to which 100 ml 4 M-HCl and 50 ml malondialdehyde bis-dimethylacetal (diluted 1 : 20 (v/v) with water) were added and the reaction allowed to proceed at room temperature overnight.…”

Section: Sample Preparation and Chemical Analysesmentioning

confidence: 99%

Effect of abomasal glucose infusion on alanine metabolism and urea production in sheep

Obitsu¹,

Bremner²,

Milne³

et al. 2000

Br J Nutr

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The effect of abomasal infusion of glucose (120 kJ/d per kg body weight (BW) 0×75 , 758 mmol/d) on urea production, plasma alanine-N¯ux rate and the conversion of alanine-N to urea was studied in sheep offered a low-N diet at limited energy intake (500 kJ/d per kg BW 0×75 ), based on hay and grass pellets. Glucose provision reduced urinary N (P = 0×040) and urea (P = 0×009) elimination but this was offset by poorer N digestibility. Urea-N production was signi®cantly reduced (822 v. 619 mmol/d, P = 0×024) by glucose while plasma alanine-N¯ux rate was elevated (295 v. 342 mmol/d, P = 0×011). The quantity of urea-N derived from alanine tended to be decreased by glucose (127 v. 95 mmol/d) but the fraction of urea production from alanine was unaltered (15 %). Plasma urea and alanine concentrations (plus those of the branched chain amino acids) decreased in response to exogenous glucose, an effect probably related to enhanced anabolic usage of amino acids and lowered urea production.

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Section: Sample Preparation and Chemical Analysesmentioning

confidence: 99%

Effect of abomasal glucose infusion on alanine metabolism and urea production in sheep

Obitsu¹,

Bremner²,

Milne³

et al. 2000

Br J Nutr

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“…Our principal interest was to develop a urea dilution method that is as precise as the earlier decribed method using [13C15Nz]urea [9] but less costly. Since the price of single labelled [13C]urea isotope is only one fifth of that of [13C15Nz]urea, and since we were able to reduce the required amount of labelled material 4-fold due to the low enrichments required in GC-IRMS analysis, the total cost of the labelled material was reduced by a factor of 20.…”

Section: Discussionmentioning

confidence: 99%

“…Natural urea and various urea isotopes have been used in these dilution studies [4-81. In a previous paper we have described a urea dilution method using the triple labelled [l3Cl5N2] urea isotope and gas chromatography-MS (GC-MS) analysis for studying urea kinetics in normal humans [9]. In patients with chronic renal failure, however, the use of the dilution method using the [13C15Nz] urea isotope is limited, since more of the costly labelled material is needed.…”

Section: Introductionmentioning

confidence: 99%

Determination of Urea Kinetics by Isotope Dilution with [13C]Urea and Gas Chromatography–isotope Ratio Mass Spectrometry (GC–IRMS) Analysis

et al. 1997

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1. Stable urea isotopes can be used to study urea kinetics in humans. The use of stable urea isotopes for studying urea kinetic parameters in humans on a large scale is hampered by the high costs of the labelled material. We devised a urea dilution for measurement of the distribution volume, production rate and clearance of urea in healthy subjects and renal failure patients using the inexpensive single labelled [13C]urea isotope with subsequent analysis by headspace chromatography-isotope ratio MS (GC-IRMS) of the [13C]urea enrichment. 2. The method involves measurement of the molar percentage excess of [13C]urea in plasma samples taken over a 4 h period after an intravenous bolus injection of [13C]urea. During the sample processing procedure, the plasma samples together with calibration samples containing a known molar percentage excess of [13C]urea are acidified with phosphoric acid to remove endogenous CO2, and are subsequently incubated with urease to convert the urea present in the plasma samples into CO2. The 13C enrichment of the generated CO2 is analysed by means of GC-IRMS. This method allows measurement of the molar percentage excess of [13C]urea to an accuracy of 0.02%. 3. Reproducibility studies showed that the sample processing procedure [within-run coefficient of variation (CV) < 2.8% and between-run CV < 8.8%] and the GC-IRMS analysis (within-day CV < 1.3% and between-day CV < 1.3%) could be repeated with good reproducibility. 4. In clinical urea kinetic studies in a healthy subject and in a renal failure patient without residual renal function, reproducible values of the distribution volume, production rate and clearance of urea were determined using minimal amounts of [13C]urea (25-50 mg). 5. Because only low [13C]urea enrichments are needed in this urea dilution method using GC-IRMS analysis, the costs of urea kinetic studies are reduced considerably, especially in patients with renal failure.

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Determination of protein catabolic rate in patients on chronic intermittent hemodialysis: Urea output measurements compared with dietary protein intake and with calculation of urea generation rate

Stegeman¹,

Huisman²,

Rouw³

et al. 1995

American Journal of Kidney Diseases

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GC-MS determination of ratios of stable-isotope labelled to natural urea using [13C15N2]urea for studying urea kinetics in serum and as a means to validate routine methods for the quantitative assay of urea in dialysate

Cited by 11 publications

References 7 publications

Effect of abomasal glucose infusion on alanine metabolism and urea production in sheep

Effect of abomasal glucose infusion on alanine metabolism and urea production in sheep

Determination of Urea Kinetics by Isotope Dilution with [13C]Urea and Gas Chromatography–isotope Ratio Mass Spectrometry (GC–IRMS) Analysis

Determination of protein catabolic rate in patients on chronic intermittent hemodialysis: Urea output measurements compared with dietary protein intake and with calculation of urea generation rate

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