Metabolism of the Human Placenta Perfused in Vitro: Glucose Transfer and Utilization, O2 Consumption, Lactate and Ammonia Production

Abstract

SummaryOxygen consumption, glucose transfer and utilization, and lactate and ammonia release were studied in the human full term placenta using an in vitro perfusion technique. DGlucose was the only substrate added to the perfusion fluid. On the maternal side, oxygen and glucose were taken up at a constant rate during perfusion. On the fetal side, a lower oxygen uptake was observed. Glucose was steadily released into the fetal perfusate as a result of the downhill concentration gradient established between maternal and fetal circulations. Bv contrast. lactate and ammonia release took place only into thematernal circulation and decreased rapidly during perfusion. No significant change in tissue glucose content was observed between the onset i d the endof the experiment. Placental lactate and ammonia concentrations were shown to diminish significantly during perfusion. Abbreviation v-a, veno-arterialThe supply of oxygen, glucose, and amino acids to the fetus has often been studied without due regard to their rate of metabolism in the placenta. There are now several lines of evidence indicating that placental metabolism interferes with the transfer of certain endogenous molecules. During transfer across the perfused human placental lobule, an extensive conversion of cortisol to cortisone has been demonstrated (4). Furthermore the lack of glutamate transfer has been interpreted as being the result of its rapid uptake and degradation by the trophoblastic membrane (19).The role of placental metabolism in relation to the supply of glucose and lactate to the fetus was studied recently in sheep. Placental tissue utilization of glucose seems to be implicated in the limitation of its materno-fetal transfer (22). Maternal lactate is transferred only in small amounts across the sheep cotyledon(l1); however, this substrate is produced by the placenta and release into the umbilical circulation (1, 23).The purpose of this study is to reexamine some aspects of transfer and metabolism in the perfused human placenta using only D-glucose as substrate. Oxygen consumption, glucose transfer and utilization, lactate and ammonia release were investigated to serve as a baseline for further studies with additional substrates. MATERIALS AND METHODSPefusion technique. Human placentae from uncomplicated pregnancies were collected after vaginal delivery at term. The perfusion technique has been described in detail by Schneider et al. (18). A suitable lobule was selected for perfusion. The fetal vessels were canulated with polyethylene catheters. Two fine canulas were inserted directly into the intervillous space over the area blenched by perfusion of fetal circulation. The maternal outflow, emerging from openings in the decidual plate, was drained outside the perfusion chamber. The perfusion was started within 30 min after delivery. Fifteen minutes were allowed to wash out the blood from the circulations, after which the experiment lasted 45 min.To allow for metabolic studies, changes in temperature control were introduced into the orieinal d...

Effects of gestational diabetes on human placental glucose uptake, transfer, and utilisation

“…The HPLC results suggest that during the time of the experiment (1.5 h), the pool of glucose used for lactate production is independent of the glucose being transported from the maternal perfusate to the fetal effluent. This is consistent with previous research suggesting the lactate released may have been synthesised, at least in part, before perfusion [16,18].…”

Glucose Uptake, Utilization, and Transfer by the Human Placenta as Functions of Maternal Glucose Concentration

“…However it is of the same order of magnitude of values measured in the fetoplacental unit of the rabbit (23) and the cow (24). Although previous studies have shown that the conditions of oxygenation used in our perfusions are within the physiological range (14,25), we still should consider the possibility that the oxygen consumption had been physically limited in our experiments. In maternal physiological conditions (4 to 7 mM arterial glucose), the maximal proportion of glucose which is retained, but not metabolized, within the placenta is very small but increases dramatically during maternal hyperglycemia (Fig.…”

“…The present study establishes the relationships that exist between placental glucose uptake from the maternal circulation, transfer to the fetal circulation and utilization, and maternal glucose concentration. The rates of glucose uptake and transfer were proportional to maternal glucose concentration up to 17-22 mM for a maternofetal gradient of [14][15][16][17][18][19] mM. Above this value both glucose uptake and transfer rates appeared to be limited.…”

“…Term human placentas were obtained from uncomplicated pregnancies after either vaginal delivery or caesarean section. The perfusion experiments were performed on an isolated lobule according to the method described by Panigel et al (13), recently adapted for metabolic studies (14). medium containing bovine serum albumin (1 g/liter).…”

TNF-α Is a Predictor of Insulin Resistance in Human Pregnancy

“…Five human placentas from uncomplicated pregnancies were collected immediately after cesarean sections. Perfusion of a suitable placental lobule was carried out as described previously (32). The placenta was washed before perfusion, and the medium was recirculated in the fetal and maternal circulation for 120 min.…”