Effect of reduced inspired oxygen on fetal growth and maternal glucose metabolism in rat pregnancy

The effect of prolonged exposure to a reduced fraction of inspired oxygen ( [FiO(2)] 0.17 for 3 days) on maternal glucose kinetics, placental glucose t ransporters GLUT1 and GLUT3, and fetal growth was examined in rat pregnancy . Arterial and venous catheters were placed 3 days before the study. [3-H-3 ]glucose tracer and deuterium labeling of water were used to measure the ra tes of glucose turnover and gluconeogenesis (GNG), respectively. Glucose up take by maternal tissues was measured using [C-14]2-deoxyglucose. Exposure to a reduced FiO(2) resulted in a significant decrease (mean +/- SE) in fet al weight (room air, 4.02 +/- 0.04 g; 0.17 FiO(2), 3.27 +/- 0.6 g, P <.02). There was a significant increase in the maternal-fetal glucose gradient (m aternal Fetal glucose ratio: room air, 1.48 +/- 0.11; 0.17 FiO(2), 2.26 +/- 0.24, P <.05), but there was no change in the maternal or fetal blood lact ate concentration. No significant change in maternal blood pH was observed; however a significant decrease in the blood partial pressure of O-2 (PO2) occurred (room air, 97 +/- 0.5 torr; 0.17 FiO(2). 81 +/- 1.8) on day 3. The re was no change in the rate of turnover of glucose or GNG in the maternal compartment, nor was there any effect on glucose uptake by the maternal tis sues. Placental GLUT1 and GLUT3 mRNA were not different in the control or e xperimental animals. We conclude that a mild reduction in the FiO(2) for 3 days in rat pregnancy results in a significant fetal growth restriction tha t is not related to any observed alteration in maternal glucose metabolism. The lower glucose concentration in the fetal brood may be the consequence of an increase in fetal glucose metabolism, thereby resulting in an increas ed maternal-fetal gradient of glucose. Copyright (C) 1999 by W.B. Saunders Company.