Surfactant metabolism in surfactant-treated preterm ventilated lambs

Abstract

Preterm lambs were delivered at 132 days gestational age, treated with 100 mg/kg radiolabeled natural sheep surfactant or Surfactant TA, and ventilated for times up to 24 h. Compared with an untreated group that developed respiratory failure by 5 h, both surfactant-treated groups had stable respiratory function to 24 h. Although only approximately 13% of the labeled surfactant phosphatidylcholine was recovered by alveolar wash at 24 h, there was no significant loss of the labeled phosphatidylcholine from the lungs. Labeled palmitic acid intravascularly injected at 1 h of age comparably labeled lung phosphatidylcholine in the three groups of lambs at 5 h; however, only approximately 0.5% of the labeled phosphatidylcholine was secreted to the air spaces of surfactant-treated lambs at 24 h. Labeled lysophosphatidylcholine given with the natural sheep surfactant was taken up by the lungs, converted to phosphatidylcholine with 30-40% efficiency, and resecreted to the air spaces, demonstrating recycling of a phospholipid. The large surfactant aggregates recovered from alveolar washes by centrifugation were surface active and contained approximately 76% of the air-space phosphatidylcholine in both surfactant-treated groups. Although clinical status was comparable, alveolar washes and surfactant subfractions from Surfactant TA-treated lambs had better surface properties than did sheep surfactant-treated lambs. These studies identified no detrimental effects of surfactant treatments on endogenous surfactant metabolism and indicated that the surfactants used for treatments were recycled by the preterm ventilated lamb lung.

Surfactant Phosphatidylcholine Half-life and Pool Size Measurements in Premature Baboons Developing Bronchopulmonary Dysplasia

“…Thus, the half-life of surfactant did not change during the first 2 wk of life in the very premature baboon. The same half-life of 35 h was found in preterm lambs using PG as tracer in alveolar washes (29). In one study in term newborn lambs, endotracheally injected 3 H-PC had a very long half-life of 6 d (30).…”

Pulmonary surfactant kinetics of the newborn infant: novel insights from studies with stable isotopes

“…In preterm ventilated lambs, surfactant treatment stimulated [ 3 H]palmitic acid incorporation into surfactant PC after correction for the increased surfactant pool. 40 However, in 3-day-old rabbits, administration of surfactant did not influence the incorporation of labeled precursor in the total lung surfactant pool. 41 In preterm infants with RDS, the half-life of PG was independent of the dose of exogenous surfactant (60 vs 120 mg kg -1 ).…”

Effect of Exogenous Surfactant on the Development of Surfactant Synthesis in Premature Rabbit Lung

“…In mechanically ventilated rabbit pups of 27 d gestation, administration of natural rabbit surfactant had no effect on the incorporation of either palmitate or glycerol into PC during the first 2 h of life (36). In mechanically ventilated lambs of 132 d gestation neither natural sheep surfactant nor surfactant TA affected the incorporation of precursor into surfactant phospholipid in the first 5 h of life (37). These last two studies were marked by physiologic instability that may have masked potential effects of surfactant.…”