Partition of maternal glucose production between conceptus and maternal tissues in sheep

Experiments were conducted in late-gestation, conscious, pregnant ewes to measure maternal glucose production and the net glucose uptake by the uterus, fetus, uteroplacenta, and nonuterine maternal tissues. Glucose concentration in the ewes varied naturally or decreased in response to fasting. Normoglycemic ewes (63.8 ± 8.7 mg/dl) had a glucose production rate of 178.7 ± 44.5 mg/min compared with a rate of 76.9 ± 20.6 mg/min for hypoglycemic ewes (34.7 ± 7.4 mg/dl). Uterine glucose uptake (56.5 ± 16.8 mg/min), fetal glucose uptake (15.7 ± 5.2 mg/min), uteroplacental glucose uptake (40.8 ± 13.4 mg/min), and nonuterine maternal glucose uptake (122.2 ± 27.7 mg/min) in the normoglycemic ewes were significantly greater than in the hypoglycemic ewes (28.7 ± 5.4, 7.5 ± 4.4, 21.2 ± 6.6, and 48.2 ± 15.2 mg/min, respectively). The fractional distribution of maternally produced glucose among nonuterine maternal tissues, the fetus, and the uteroplacenta was not altered markedly by hypoglycemia despite a 57% reduction in maternal glucose production.