The present study was undertaken to assess the role of hepatic glycogen metabolism in fetal and maternal glucose homeostasis during a prolonged fast in the pregnant ewe. A control fed group of 13 ewes and 16 fetuses were compared to a 5-day-fasted group of 13 ewes and 17 fetuses, studied at 125 days gestation (term = 147 days). Tissue samples were obtained during pentobarbital anesthesia and frozen in liquid nitrogen. Protein, glycogen, active phosphorylase and total phosphorylase activity were determined. Fetal weight (3.61 vs. 2.86 kg) was decreased in the fasted group (p < 0.001) while fetal hepatic glycogen was unchanged (59.8 vs. 52.4 mg/g tissue). Maternal liver glycogen decreased during fasting (38.2 vs. 4.0 mg/g tissue, p < 0.001). Fetal active phosphorylase and total phosphorylase did not change between fed and fasted states (fed active phosphorylase 398 vs. fasted 441 and fed total phosphorylase 510 vs. fasted 574 μmol/h/g tissue). The maternal active phosphorylase and total phosphorylase decreased between fed and fasted (active phosphorylase 690 vs. 238 and total phosphorylase 981 vs. 599 μmol/h/g tissue, p < 0.001). During fasting, the pregnant ewe depletes her hepatic glycogen stores, associated with a reduction in glycogen catabolizing enzyme activity. The fetus maintains a relatively large glycogen catabolizing enzyme activity, a relatively large glycogen reserve and substantial phosphorylase activity.
- Ovine fetus
ASJC Scopus subject areas
- Developmental Biology
- Pediatrics, Perinatology, and Child Health