A new recycling technique for human placental cotyledon perfusion: Application to studies of the fetomaternal transfer of glucose, inulin, and antipyrine

A previously described technique has been modified to permit the continuously recirculating perfusion of the separate maternal and fetal circulations of an isolated cotyledon of human placenta. Viability of the perfused cotyledons was established by measurements of oxygen consumption (average, 0.18 ml/gm/hr), glucose utilization (average, 1.0 mg/gm/hr), and lactate production (<0.01 μmol/gm/hr), and integrity of the placental barrier by the failure of India ink,125I-albumin, or35S-sulfobromophthalein to cross from fetal to maternal circulation. Clearance of3H-inulin from the fetal circuit, 0.0059 ± 0.0005 (SE) ml/min/gm, corresponded to 2.5% of its clearance by the adult human kidney. Clearance of14C-antipyrine was 0.013 ± 0.003 ml/min/gm. After introduction into the fetal circuit, the observed appearance of both inulin and antipyrine in the maternal circuit closely paralleled curves predicted by a dimple mathematical model. The use of a continuously recirculating perfusion system is technically feasible, and has advantages over the single-pass technique for studying transplacental transfer of metabolites with a low efficiency of extraction.