Equine uteroplacental metabolism at mid- and late gestation

Uptakes of oxygen, glucose and lactate by the gravid uterus, fetus and uter oplacental tissues were measured in chronically catheterized pregnant ponie s and their fetuses at mid- and late gestation (term approximate to 335 day s). Rates of O-2 uptake by the gravid uterus, fetus and uteroplacental tiss ues were significant at both gestational ages and were 2- to 3-fold higher in late gestation than the mid-gestation values of 3338 +/- 794, 1352 +/- 2 58 and 2035 +/- 602 mu mol min(-1), respectively (n = 4). Similarly, there were significant uptakes of glucose by the gravid uterus, fetus and uteropl acental tissues at both mid- and late gestation. However, unlike O-2 uptake , glucose uptake by the uterus and uteroplacental tissues did not increase between mid- and late gestation. No significant uptakes or outputs of lacta te were observed by the uterus or uteroplacental tissues at either gestatio nal age, although there was a significant umbilical uptake of lactate in la te but not mid-gestation. There was no change in the distribution of uterin e O-2 uptake between the fetus and uteroplacental tissues with increasing g estational age. The uteroplacental tissues accounted for about 50% of the u terine O-2 uptake at both gestational ages. In contrast, the proportion of the uterine glucose uptake used by the uteroplacental tissues decreased fro m 73.2 +/- 2.1% (n = 5) at mid-gestation to 61.1+/-1.9% (n = 4, P < 0.02) i n late gestation. The gestational changes in uteroplacental carbohydrate me tabolism in the mare differ from those seen in the ewe and may have importa nt consequences for the duration and outcome of pregnancy in the mare.