AJP - Regulatory, Integrative and Comparative Physiology, Vol 268, Issue 2 303-R309, Copyright © 1995 by American Physiological Society
Oxygen, glucose, and lactate uptake by fetus and placenta during prolonged hypoxemia
S. B. Hooper, D. W. Walker and R. Harding
Department of Physiology, Monash University, Clayton, Victoria, Australia.
Our aim was to compare the effects of short (4 h) and prolonged (24 h)
periods of reduced uterine blood flow (RUBF) on fetal and placental uptake
of O2, glucose, and lactate. In pregnant sheep, uterine and umbilical blood
flows were measured under normal conditions and after 4 and 24 h of RUBF. A
50% reduction in uterine blood flow caused a 56% reduction in fetal
arterial O2 saturation (SaO2). Umbilical blood flow increased from 325 +/-
33 to 378 +/- 32 ml.min-1.kg-1 (P < 0.05) after 4 h but was not
different from pre-RUBF values after 24 h. O2 uptake by the gravid uterus
was not altered by RUBF, due to an increase (84%) in uterine O2 extraction.
Similarly, uteroplacental and fetal O2 consumptions and fetal glucose
uptake were not affected by RUBF, whereas uteroplacental glucose uptake was
significantly reduced after 4 h (by 42%) and 24 h (by 58%) of RUBF. Fetal
lactate uptake was greatly reduced from 78.7 +/- 15.5 to -167 +/- 57
mumol.min-1.kg-1 after 4 h and to -198 +/- 80 mumol.min-1.kg-1 after 24 h
of RUBF; negative values indicate placental lactate uptake from the fetal
circulation. Thus, although RUBF significantly reduced fetal SaO2, fetal
and uteroplacental O2 consumptions did not change. In addition, although
fetal glucose uptake was not altered by RUBF, during RUBF the placenta
became a major site of lactate clearance from the fetal circulation.
