### Abstract

The isotope dilution technique for measuring total body water (TBW), and the doubly labelled water (DLW) method for measuring energy expenditure, are both sensitive to small variations in the ratio of the hydrogen to oxygen-18 dilution space. Since the dilution space ratio varies between individuals, there has been much recent debate over what causes this variability (i.e. physiological differences between individuals or analytical error in the isotope determinations), and thus which values (individual or a population mean dilution space ratio) should be employed for TBW and DLW calculations. To distinguish between physiological and analytical variability, we injected 15 non-reproductive and 12 lactating mice (Mus musculus, outbred MF1) simultaneously with deuterium, tritium and oxygen-18, The two hydrogen labels were administered and analysed independently, therefore we expected a strong correlation between dilution space ratios based on deuterium and tritium if most of the variation in dilution spaces was physiological, but only a weak correlation if most of the variation was analytical. Dilution spaces were significantly influenced by reproductive status. Dilution spaces expressed as a percentage of body mass averaged 15.7 % greater in lactating mice than in non-reproductive mice. In addition, the hydrogen tracer employed had a significant effect (deuterium spaces were 2.0 % larger than tritium spaces). Deuterium and tritium dilution spaces, expressed as a percentage of body mass, were highly correlated. Dilution space ratios ranged from 0.952 to 1.146 when using deuterium, and from 0.930 to 1.103 when using tritium, Dilution space ratios based on deuterium and tritium were also highly correlated. Comparison of standard deviations of the dilution space ratio based on deuterium in vivo and in vitro indicated that only 4.5 % of the variation in the dilution space ratios observed in the mice could be accounted for by analytical variation in the deuterium and oxygen-18 analyses. Although our results include data which were outside the limits previously regarded as biologically possible, the correlations that we detected strongly suggest that variation in the observed dilution space ratio was mostly physiological rather than analytical.

Original language | English |
---|---|

Pages (from-to) | 2839-2849 |

Number of pages | 11 |

Journal | Journal of Experimental Biology |

Volume | 202 |

Publication status | Published - 1999 |

### Keywords

- dilution space ratio
- total body water
- body composition
- energy expenditure
- doubly labelled water
- breath samples
- mouse
- Mus musculus
- DOUBLY LABELED WATER
- TOTAL-BODY WATER
- TOTAL-ENERGY-EXPENDITURE
- HEART-RATE
- CARBON-DIOXIDE
- CO2 PRODUCTION
- VALIDATION
- SEALS
- O-18
- EQUATIONS

### Cite this

**Isotope dilution spaces of mice injected simultaneously with deuterium, tritium and oxygen-18.** / Krol, E ; Speakman, J R .

Research output: Contribution to journal › Article

*Journal of Experimental Biology*, vol. 202, pp. 2839-2849.

}

TY - JOUR

T1 - Isotope dilution spaces of mice injected simultaneously with deuterium, tritium and oxygen-18

AU - Krol, E

AU - Speakman, J R

PY - 1999

Y1 - 1999

N2 - The isotope dilution technique for measuring total body water (TBW), and the doubly labelled water (DLW) method for measuring energy expenditure, are both sensitive to small variations in the ratio of the hydrogen to oxygen-18 dilution space. Since the dilution space ratio varies between individuals, there has been much recent debate over what causes this variability (i.e. physiological differences between individuals or analytical error in the isotope determinations), and thus which values (individual or a population mean dilution space ratio) should be employed for TBW and DLW calculations. To distinguish between physiological and analytical variability, we injected 15 non-reproductive and 12 lactating mice (Mus musculus, outbred MF1) simultaneously with deuterium, tritium and oxygen-18, The two hydrogen labels were administered and analysed independently, therefore we expected a strong correlation between dilution space ratios based on deuterium and tritium if most of the variation in dilution spaces was physiological, but only a weak correlation if most of the variation was analytical. Dilution spaces were significantly influenced by reproductive status. Dilution spaces expressed as a percentage of body mass averaged 15.7 % greater in lactating mice than in non-reproductive mice. In addition, the hydrogen tracer employed had a significant effect (deuterium spaces were 2.0 % larger than tritium spaces). Deuterium and tritium dilution spaces, expressed as a percentage of body mass, were highly correlated. Dilution space ratios ranged from 0.952 to 1.146 when using deuterium, and from 0.930 to 1.103 when using tritium, Dilution space ratios based on deuterium and tritium were also highly correlated. Comparison of standard deviations of the dilution space ratio based on deuterium in vivo and in vitro indicated that only 4.5 % of the variation in the dilution space ratios observed in the mice could be accounted for by analytical variation in the deuterium and oxygen-18 analyses. Although our results include data which were outside the limits previously regarded as biologically possible, the correlations that we detected strongly suggest that variation in the observed dilution space ratio was mostly physiological rather than analytical.

AB - The isotope dilution technique for measuring total body water (TBW), and the doubly labelled water (DLW) method for measuring energy expenditure, are both sensitive to small variations in the ratio of the hydrogen to oxygen-18 dilution space. Since the dilution space ratio varies between individuals, there has been much recent debate over what causes this variability (i.e. physiological differences between individuals or analytical error in the isotope determinations), and thus which values (individual or a population mean dilution space ratio) should be employed for TBW and DLW calculations. To distinguish between physiological and analytical variability, we injected 15 non-reproductive and 12 lactating mice (Mus musculus, outbred MF1) simultaneously with deuterium, tritium and oxygen-18, The two hydrogen labels were administered and analysed independently, therefore we expected a strong correlation between dilution space ratios based on deuterium and tritium if most of the variation in dilution spaces was physiological, but only a weak correlation if most of the variation was analytical. Dilution spaces were significantly influenced by reproductive status. Dilution spaces expressed as a percentage of body mass averaged 15.7 % greater in lactating mice than in non-reproductive mice. In addition, the hydrogen tracer employed had a significant effect (deuterium spaces were 2.0 % larger than tritium spaces). Deuterium and tritium dilution spaces, expressed as a percentage of body mass, were highly correlated. Dilution space ratios ranged from 0.952 to 1.146 when using deuterium, and from 0.930 to 1.103 when using tritium, Dilution space ratios based on deuterium and tritium were also highly correlated. Comparison of standard deviations of the dilution space ratio based on deuterium in vivo and in vitro indicated that only 4.5 % of the variation in the dilution space ratios observed in the mice could be accounted for by analytical variation in the deuterium and oxygen-18 analyses. Although our results include data which were outside the limits previously regarded as biologically possible, the correlations that we detected strongly suggest that variation in the observed dilution space ratio was mostly physiological rather than analytical.

KW - dilution space ratio

KW - total body water

KW - body composition

KW - energy expenditure

KW - doubly labelled water

KW - breath samples

KW - mouse

KW - Mus musculus

KW - DOUBLY LABELED WATER

KW - TOTAL-BODY WATER

KW - TOTAL-ENERGY-EXPENDITURE

KW - HEART-RATE

KW - CARBON-DIOXIDE

KW - CO2 PRODUCTION

KW - VALIDATION

KW - SEALS

KW - O-18

KW - EQUATIONS

M3 - Article

VL - 202

SP - 2839

EP - 2849

JO - Journal of Experimental Biology

JF - Journal of Experimental Biology

SN - 0022-0949

ER -