254 CORRELATIONS OF GROWTH(G), LUNG PHOSPHATIDYLCHOLINE (PC), AND LUNG PROTEIN(PR) IN NEWBORN RABBITS

Abstract

Upon delivery, surfactant is released into the airway of newborn animals. However, changes in total lung (TL), alveolar wash (AW), and lung parenchyma (LP) PC, saturated PC (SPC), and LP PR have not been correlated with early neonatal G. We sacrificed 5 newborn rabbits per day taken from different healthy litters on days 1-12 of life. Following a standardized lung wash we measured in duplicate LP and AW PC, SPC and PR. Samples for the PC and SPC measurements contained 14C-SPC to correct for losses in processing. The rabbits grew from 53±3 g to 240±20 g in 12 days (G curve: Y=51e 0.1315t, r=0.986). TL PC increased from 13±1 μmoles to 34±4 μmoles by 12 days (PC curve: Y=11 + 3.87t -0.16t2, r=.958). AW PC increased for only about 4 days, then the majority of the increase in TL PC was due to an increase in the LP pool. The LP PR increased from 78.2±2.9 to 194±23 mg by 12 days (PR curve: Y=84.8 -9.2t + 3.8t2 -0.2t3, r=0.984). The curves for increases in G, PC, and PR are complex and nonlinear. However, for example, expressing AW PC and LP PC relative to weight results in linear curves (r=0.846 and r=0.930, respectively) that “hide” time dependent nonlinear changes in the pool sizes. However, SPC/PC in LP (0.340±0.003) and SPC/PC in AW (0.612±0.009) were invariant. While there are complex changes in pool sizes of protein and phosphatidylcholine relative to growth, the ratios of LP and AW SPC to PC are tightly regulated.