Uterine metabolism of the pregnant rabbit under chronic steady-state conditions

The study of uterine metabolism in pregnancy under chronic steady-state conditions has been confined to large mammals and, more recently, to the guinea pig. The pregnant rabbit is of interest because of its short gestation and large litter size. We developed an indirect approach involving retrograde catheterization of the uterine venous drainage, permitting measurement of both uterine metabolic quotients and uterine uptakes. Radioactive microspheres were used to measure blood flow. A large lactate and ammonia efflux from the uterus was found. In the fed state, ketogenic substrates were taken up in small amounts. However, during starvation a significant increase in ketoacid uptake was observed with a concurrent fall in acetate uptake. There was a large glucose/oxygen quotient across the uterus, but the glucose plus lactate/oxygen quotient was comparable to that found in the sheep and guinea pig (0.6 +/- 0.1). It is apparent that in all three species studied under chronic steady-state conditions (sheep, guinea pig, and rabbit) there is a large glucose uptake associated with a net lactate production, and fuels other than glucose and lactate must be used by the uterus.