Am. J. Respir. Crit. Care Med., Volume 160, Number 5, November 1999, 1481-1485

Metabolism of Endogenous Surfactant in Premature Baboons and Effect of Prenatal Corticosteroids

JAN ERIK H. BUNT, VIRGILIO P. CARNIELLI, STEVEN R. SEIDNER, MACHIKO IKEGAMI, J. L. DARCOS WATTIMENA, PIETER J. J. SAUER, ALAN H. JOBE, and LUC J. I. ZIMMERMANN

Division of Neonatology, Department of Pediatrics, Sophia Children's Hospital/University Hospital Rotterdam/Erasmus University Rotterdam, Rotterdam, The Netherlands; Division of Neonatology, Department of Pediatrics, University Hospital Padova, Padua, Italy; University of Texas Health Science Center, San Antonio, Texas; Pulmonary Biology, Children's Hospital Medical Center, Cincinnati, Ohio; Department of Internal Medicine II, Erasmus University Rotterdam, Rotterdam, The Netherlands; and Department of Pediatrics, University Hospital Groningen, Groningen, The Netherlands

We studied the synthesis of surfactant and the effect of prenatal betamethasone treatment in vivo in very preterm baboons. Ten pregnant baboons were randomized to receive either betamethasone (beta) or saline (control) 48 and 24 h before preterm delivery. The newborn baboons were intubated, treated with surfactant, and ventilated for 6 d. They received a 24-h infusion with the stable isotope [U-¹³C]glucose as precursor for the synthesis of palmitic acid in surfactant phosphatidylcholine (PC). Palmitic acid in surfactant PC became enriched 27 ± 2 h after the start of the isotope infusion and was maximally enriched at 100 ± 4 h. The fractional synthesis rate of PC palmitate in the beta group (1.5 ± 0.2%/d) was increased by 129% above control (0.7 ± 0.1%/d) (p < 0.02, Mann- Whitney U test). The absolute synthesis rate of PC in the beta group [1.6 ± 0.3 µmol/kg/d] was increased by 128% above controls [0.7 ± 0.2 µmol/kg/d] (p < 0.02). These data show that the synthesis of endogenous surfactant from plasma glucose as precursor is a slow process. It is shown, for the first time in vivo, that prenatal glucocorticosteroids stimulate the synthesis of surfactant PC in the very premature baboon. Bunt JEH, Carnielli VP, Seidner SR, Ikegami M, Wattimena JLD, Sauer PJJ, Jobe AH, Zimmermann LJI. Metabolism of endogenous surfactant in premature baboons and effect of prenatal corticosteroids.

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