Metabolite concentrations in human term placentae and their changes due to delayed collection after delivery

The present study was designed to quantify the major cellular metabolites in human placentae and their changes due to the confounding effect of time and subsequent hypoxia during sample collection using magnetic resonance spectroscopy ((1)H-and (31)P-MRS). The absolute placental concentrations of lactate, glucose, major amino acids and cellular volume/osmo-regulators, glutathione, high-energy phosphates, fatty acids, phospholipids, triglycerols, and cholesterol are reported. There were no spatial differences in metabolism or protein expression throughout the placenta. The most significant temporal changes, due to the collection time (from 1 to 25 min after delivery), were increased concentrations of lactate (r=0.996, statistically significant P< 0.01 after 11 min) and decreased concentration of glucose and ATP (r=-0.963 and -0.97, respectively, P< 0.01 after 11 min). The placental samples from the later collection groups (16-24 min) had also significantly lower level of NAD(+) (r=-0.95, P< 0.01). Only the latest collection group (21-24 min) had increased lipid peroxidation and changes in lipid metabolites (P< 0.01). We conclude that the optimal window for collecting placental tissue without incurring metabolic artifacts due to hypoxic conditions is within 9 min of placental delivery.