Uptake and metabolism of prostaglandin E 1 in isolated pzbfuseb petal, newborn and adult rabbit lungs

Abstract

PGE 1 has been used to maintain the patency of the ductus arteriosus in newborns with pulmonary hypertension. However, it is known that adult lungs avidly take up and metabolize circulating PGE 1. We compared the ability of isolated perfused lungs from previable, 26-day gestation, fetal rabbits; newborn rabbits (within 12 hours of birth) and 3 month old adult rabbits to metabolize a 20-second bolus of PGE 1. The concentration of PGE 1 infused was approximately 2 orders of magnitude below the Km for the PGE 1 uptake process so that first order uptake kinetics are assured. The retention time of a vascular marker dye was monitored as an index of pulmonary vascular surface area. In all three sizes of lungs perfusate flow was adjusted to produce an approximately 7 second dye retention time. At these flows the adult lungs inactivate about 45 percent of the infused PGE 1. In contrast, fetal and newborn rabbit lungs both inactivate about 22 percent of the infused PGE 1. We conclude that the ability of the lung to take up and metabolize circulating PGE 1 is markedly reduced in premature and term newborns.