Abstract
Glucose (Glu) levels are exceedingly low in the ovine fetus and the ungulate liver has little measurable glucokinase. Nonetheless, at term, the fetal (Fet) sheep liver contains significant glycogen stores. Recent suggestions that glycogenesis in the adult may proceed through the gluconeogenic pathway led us to examine the capacity of lactate (Lac) to serve as a glycogenic precursor in the chronically catheterized Fet sheep. Six ovine fetuses were prepared with aortic (Ao) and inferior vena cava (IVC) catheters. On day 5 post surgery, after a maternal (Mat) 48 hour fast, a steady state Mat venous infusion of Glu was begun sufficient to raise Mat blood Glu from 19.41.6 mg/dl to 48.6±6.2 mg/dl. A simultaneous infusion of 300 uC (U-14C) Lac was administered to the Fet IVC over a 5 hour period to steady state. Six Fet Ao and Mat art. samples were obtained q 10 min during the last 60 min of the infusion. The fetus and ewe were then sacrificed and liver removed for determination of glycogen and 14C glycogen enrichment. Minimal radiolabel was found in Mat blood or liver glycogen. Fet blood levels were Lac 13.6±1.3 mg/dl (SA 42±9 uc/mg×103), fructose 70.2±10.4 mg/dl (SA 1.0±.2 uc/mg×103), Glu 23.2±4.3 mg/dl. No Lac-derived labelled Fet Glu could be reliably detected. Fet hepatic glycogen was 40.0±6.5 mg/g liver (SA 1.4±.5 uc/mg×103). The SA of glycogen and absent Glu labelling suggests that Lac is a precursor of Fet glycogen through the gluconeogenic path. This is teleologically important, since placental conversion of Mat Glu to Lac maintains higher levels of Lac in the Fet circulation and seems to be a means for Fet conservation of energy stores.
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Levitsky, L., Paton, J. & Fisher, D. 1228 LACTATE IS A GLYCOGENIC PRECURSOR IN THE OVINE FETUS. Pediatr Res 19, 315 (1985). https://doi.org/10.1203/00006450-198504000-01258
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DOI: https://doi.org/10.1203/00006450-198504000-01258