The effects of mild hypoxemia on fetal growth and maternal glucose kinetics& uptake and placental glucose transporters (GLUT 1 & 3) were examined in chronically catheterized pregnant rats. The animals were placed in 17% FIO2 from day 17 to 20 of gestation. The rate of glucose turnover was measured using [3-3H]glucose tracer infusion. Gluconeogenesis was estimated using deuterated water method. Glucose uptake by various maternal tissues was quantified using [U-14C] 2-deoxyglucose according to the method of Sokoloff. Placental GLUT 1 & 3 mRNA were determined in 4 hypoxemic and 5 control litters. Mild hypoxemia for 3 days resulted in a significant reduction in fetal weight [3.58±0.12 gm (n=12 litters) vs. 4.02±0.11 gm (n=9), mean+SEM, p<0.02] and a significant increase in maternal to fetal glucose gradient [2.6±0.24 (n=4) vs 1.48±0.11(n=5), p<0.05]. There was no change in the rate of glucose production or gluconeogenesis. In addition, there was no significant effect of hypoxia on placental GLUT 1 mRNA [0.89±0.1 (n=4) vs. 1.0±0.03 (n=5)] or GLUT 3 mRNA [1.22±0.15 (n=4) vs. 1.0±0.06 (n=5)].Table

Table 1

We conclude that prolonged mild hypoxemia for 3 days significantly reduces fetal growth. This effect is associated with increased maternal fetal glucose gradient without detectable effect on maternal glucose kinetics or glucose utilization by maternal tissues. The increased maternal fetal gradient may reflect an increase in placental fetal glucose consumption, which may contribute to fetal growth retardation.