PLACENTAL DIFFUSING-CAPACITY AND FETAL DEVELOPMENT IN EXERCISING OR HYPOXIC GUINEA-PIGS

We studied either chronic exercise or chronic environmental hypoxia on placental carbon monoxide diffusing capacity (Dpco) in guinea pigs. Hartley guinea pigs with dated pregnancies were exercised moderately on a treadmill (10 m/min at an 8% grade for 15 min twice a day) or were exposed to hypoxia (12% O2) throughout the course of gestation. We measured Dpco, fetal body, heart, and brain weights, placental weight, and maternal body and heart weights near term (62-64 days). All parameters were compared to a control group of pregnant guinea pigs. Exercise at this level produced no changes in fetal body, organ, or placental weights. Hypoxia, on the other hand, caused a reduction in fetal body and brain weight, and an increase in the Dpco of brain, heart, and placenta weights to body weight. Dp in the exercise group decreased 34% to 2.16 ± 0.11 ml/(min x Torr x kg fetal wt) from a control value of 3.27 ± 0.10 ml/(min x Torr x kg). In the hypoxic group Dpco increased 63% to 5.33 ± 0.14 ml/(min x Torr x kg). Placental microsomal cytochrome P-450 concentrations were low in control animals and did not increase with hypoxia; thus, cytochrome P-450 apparently played no role in the increased placental Dpco with hypoxia.