Condition and performance of the perfused human placental cotyledon.

The perfused human placental cotyledon was examined with respect to its viability, metabolic state, and performance. During the ischemic period before the start of perfusion, tissue adenosine triphosphate concentration and other measures of energy state fell rapidly to about half of the estimated in vivo value. During the subsequent perfusion, energy levels remained relatively stable but did not recover appreciably toward in vivo values. A very low transplacental leakage of inulin and a small cellular potassium loss indicate relative intactness of membrane function, but there were differences from the in vivo state in levels and balance of metabolic regulators adenosine triphosphate, adenosine monophosphate, and adenosine triphosphate/adenosine monophosphate ratio, and a more reduced cytoplasmic reduced nicotinamide adenine dinucleotide/ionized nicotinamide adenine dinucleotide couple. However, rates of oxygen and glucose consumption and lactate production and the maintenance of physiologic upward maternal-to-fetal concentration gradients of amino acids lead us to conclude that despite differences in energy and metabolic states the perfused cotyledon remains substantially intact and functions in certain respects comparably with the in vivo state.