Estimation of glucose kinetics in fetal-maternal studies: Potential errors, solutions, and limitations
- Children's Hospital Medical Center, Cincinnati, OH (USA)
We investigated whether errors occur in the estimation of ovine maternal-fetal glucose (Glc) kinetics using the isotope dilution technique when the Glc pool is rapidly expanded by exogenous (protocol A) or endogenous (protocol C) Glc entry and sought possible solutions (protocol B). In protocol A (n = 8), after attaining steady-state Glc specific activity (SA) by (U-14C)glucose (period 1), infusion of Glc (period 2) predictably decreased Glc SA, whereas. (U-14C)glucose concentration unexpectedly rose from 7,208 +/- 367 (means +/- SE) in period 1 to 8,558 +/- 308 disintegrations/min (dpm) per ml in period 2 (P less than 0.01). Fetal endogenous Glc production (EGP) was negligible during period 1 (0.44 +/- 1.0), but yielded a physiologically impossible negative value of -2.1 +/- 0.72 mg.kg-1.min-1 during period 2. When the fall in Glc SA during Glc infusion was prevented by addition of (U-14C)glucose admixed with the exogenous Glc (protocol B; n = 7), EGP was no longer negative. In protocol C (n = 6), sequential infusions of four increasing doses of epinephrine serially decreased SA, whereas tracer Glc increased from 7,483 +/- 608 to 11,525 +/- 992 dpm/ml plasma (P less than 0.05), imposing an obligatory underestimation of EGP. Thus a tracer mixing problem leads to erroneous estimations of fetal Glc utilization and Glc production via the three-compartment model in sheep when the Glc pool is expanded exogenously or endogenously. These errors can be minimized by maintaining the Glc SA relatively constant.
- OSTI ID:
- 6643032
- Journal Information:
- American Journal of Physiology; (USA), Vol. 258; ISSN 0002-9513
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GLUCOSE
METABOLISM
ADRENALINE
CARBON 14 COMPOUNDS
DATA COVARIANCES
FETUSES
ISOTOPE DILUTION
MATHEMATICAL MODELS
MEMBRANE TRANSPORT
PREGNANCY
SHEEP
TRACER TECHNIQUES
ADRENAL HORMONES
ALDEHYDES
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
CARBOHYDRATES
CARDIOTONICS
CARDIOVASCULAR AGENTS
DOMESTIC ANIMALS
DRUGS
HEXOSES
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
MAMMALS
MONOSACCHARIDES
NEUROREGULATORS
ORGANIC COMPOUNDS
RUMINANTS
SACCHARIDES
SYMPATHOMIMETICS
VERTEBRATES
550501* - Metabolism- Tracer Techniques