Abstract
In adults glucose (glu) incorporation to glycogen (glyc) is indirect following recycling from lactate. In neonates galactose (gal) entry to glyc exceeds that for glu but the pathway is unknown. The path of hexose incorporation to glyc was studied in 5-7 day old rats and 6 hr old rats injected (IP) with either double labeled [6-3H (nonrecycle) U-14C (recycle)]-glu or (6-3H)-glu and (U-14C)-gal in saline (S), N=8-15. In another group of rats 1g/kg of glu or gal was used to determine glycemia and glyc synthesis at 15′ to 180′. Glu increased from 3.4±0.4 to 8.5±1.5mM in 5-7 day pups in response to IP glu; there was no glycemic response to gal, although gal levels increased from 0.5 to 6.3 mM at 15′. Glyc increased after IP glu from 14±2 at 15′ to 30±3 at 120′, (p<0.01) while after IP gal glyc was 44±6 umol/g at 120′, p<0.05. After IP glu, 3H and 14C dpm in glyc increased slowly with 14C exceeding H at 120′ and 180′. In contrast IP 14C gal resulted in a large peak of 14C incorporation to glyc which was 5 fold greater than that after 14C glu. The ratio of 3H;14C in glyc relative to the injectate after IP glu decreased from 0.69±0.12 to 0.36±0.03, p<0.01 between 15′ to 180′ while the ratio after gal was 0.06±0.007 to 0.15±0.02. 6 hr old pups also demonstrated augmented incorporation of 14C gal in glyc relative to 3H14C glu. In contrast to 5-7 day pups there was no evidence of glu recycling in 6 hr. pups. In conclusion, gal entry into glyc exceeds that for glu and is not dependent on recycling. Direct incorporation of gal exceeds that for direct incorporation from 3H glu suggesting a preferential diversion of gal for neonatal glyc synthesis.
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Kunst, C., Kliegman, R. & Trindade, C. THE GALACTOSE-GLUCOSE “PARADOX” IN NEONATAL MURINE HEPATIC GLYCOGEN SYNTHESIS. Pediatr Res 21 (Suppl 4), 343 (1987). https://doi.org/10.1203/00006450-198704010-01058
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DOI: https://doi.org/10.1203/00006450-198704010-01058