Comparison of lactate and glucose metabolism in the developing porcine placenta

The present experiment was conducted to determine whether lactate is an important metabolic substrate for the developing porcine placenta. Pregnant gilts were anesthetized with pentobarbital sodium (5 mg/kg) at 65, 85, or 110 days of gestation and underwent an abdominohysterectomy. Fetal and maternal placental tissues were obtained and isolated for enzyme analysis and tissue incubations. Tissues were incubated for 2 h in Krebs-Ringer bicarbonate buffer containing 10 mM glucose, 1.0 mM Na-palmitate, 2.0 mM L-lactate, and 2% albumin. The incorporation of glucose or lactate into CO2, total lipids, and fatty acids was examined by radioactive tracers. Lactate was shown to be at least as important a substrate as glucose for utilization through these metabolic pathways in both the fetal and maternal placentas during gestation. This ability to metabolize lactate may serve as a conservation mechanism to spare other nutrients for transfer to the fetus. Additionally, analysis of enzyme and incubation data indicated that the fetal and maternal placenta follow different developmental patterns, implying the origins for (or mechanisms of) regulation of these two tissues may differ.