Biochemical and physiological development of fetal rhesus lung.

Study of 17 fetal rhesus monkeys (Macaca mulatta) revealed a sequential rise in lung phosphatidylcholine (PC) concentration due to elevations in both disaturated (DSPC) and unsaturated constituents. The % DSPC in lung tissue clinical abruptly at 145 days of gestation prior to significant increases in PC or DSPC concentration but in association with improved lung deflation stability (% V10). This suggests that the DSPC-to-PC ratio may be a sensitive biochemical indicator of surfactant phospholipid production in lung parenchyma. Phosphatidyl-glycerol content did not increase significantly until after 155 days gestation, which was coincident with maximizing pulmonary distensibility (V max). Declining levels of phosphatidylethanolamine and sphingomyelin in lung tissue at 162 days support the hypothesis that preferential synthesis of PC occurs during late gestation. A serial decline in lung glycogen content with advancing gestation may reflect glycogen utilization as a substrate for lung phospholipid production. Comparison of biochemical and physiological data confirms the impression that discordances occur among lung maturational events. Lastly, a relationship between rising fetal blood cortisol levels and indices of fetal lung development was not demonstrated.