Plasma platelet activating factor acetylhydrolase in preterm and term neonates

Objectives: Platelet activating factor (PAF) may play a role in the pathogenesis of necrotizing enterocolitis. PAF is metabolized by the enzyme PAF acetylhydrolase to the biologically inactive lyso-PAF. We sought to characterize the changes of plasma PAF acetylhydrolase activity during the perinatal period. Methods: We determined plasma PAF acetylhydrolase activity sequentially during the first 3 weeks after birth in 35 neonates of different gestational age, and in adult subjects. Results: Very immature preterm neonates (n = 11, 28.2 ± 0.4 weeks at birth) had a plasma PAF acetylhydrolase activity of 9.8 ± 1.4 nmol min^-1 ml^-1 at 1-2 days after birth. PAF acetylhydrolase activity in larger preterm neonates (n = 14, 32.6 ± 0.3 weeks) and term neonates (n = 10, 39.7 ± 0.2 weeks) was 13.0 ± 2.6 and 13.8 ± 2.5 nmol min^-1 ml^-1, respectively. Maternal plasma PAF acetylhydrolase activity (n = 7) measured soon after delivery was higher than neonatal values (25.0 ± 1.4 nmol min^-1 ml^-1, p < 0.01). Plasma PAF acetylhydrolase activity increased similarly in the three groups of neonates and at 1 week after birth did not differ from maternal values. Neonatal and maternal PAF acetylhydrolase activities were lower than that of normal non-pregnant adults (males 53.0 ± 6.1, females 38.012.4 nmol min^-1 ml^-1). Conclusions: The activity of the enzyme that metabolizes PAF is decreased during the perinatal period. The lower activity of plasma PAF acetylhydrolase may predispose neonates to disease mediated by PAF.