Platelet-activating factor acetylhydrolase in term and preterm human milk: a preliminary report.

Human milk may protect against necrotizing enterocolitis (NEC). Since platelet-activating factor (PAF) may participate in the pathophysiology of NEC, we measured PAF acetylhydrolase (PAF-AH), which metabolizes PAF, in term and preterm human milk. The activity of PAF-AH in term milk collected 2-4 days after delivery (n = 17) was 2.7 +/- 1.2 nmol x min-1 x ml-1. A higher activity was found in milk collected at similar times from mothers who delivered between 33 and 36 weeks of gestation (n = 6, 5.6 +/- 2.1 nmol x min-1 x ml-1, p < 0.01). However, milk from mothers who delivered between 26 and 32 weeks of gestation had a PAF-AH activity similar to that of term milk (n = 6, 3.0 +/- 0.7 nmol x min-1 x ml-1). With advancing lactational age, PAF-AH activity in term milk decreased, whereas the activity of this enzyme in preterm milk remained unchanged. In milk samples collected beyond 14 days after delivery from women who gave birth between 33 and 36 weeks or 26 and 32 weeks of gestation, PAF-AH activity was fivefold higher than that found in milk for women delivering at term (3.7 +/- 1.3 and 3.6 +/- 3.6 nmol x min-1 x ml-1 serum 0.7 +/- 0.4 nmol x min-1 x ml-1, respectively, p < 0.05). We speculate that the presence of PAF-AH in human milk may protect against NEC in preterm newborns.