Absorption of platelet-activating factor acetylhydrolase by rat intestine.

Platelet-activating factor acetylhydrolase (PAF-AH) is a 43-kDa protein that catalyzes the degradation and inactivation of this potent phospholipid mediator. PAF plays an important role in the pathogenesis of necrotizing enterocolitis (NEC), and the elevation of the plasma PAF-AH activity may be beneficial in the prevention of this disease. The activity of PAF-AH was transferred from the mucosal to the serosal fluid in intestinal sacs from neonatal rats. Translocation was highest on day 15, decreased by day 21, and disappeared by day 24. Greater transport of the enzyme was noted in the neonatal jejunum compared with duodenum or ileum. PAF-AH absorption in 15-day-old rats was decreased by the addition of inhibitors of energy production and by low temperature. We have, therefore, concluded that the enzyme transport is an energy-dependent process. It is suggested that PAF-AH found in milk may prove to be beneficial in the prevention of NEC by its translocation across the intestinal mucosa. The absorption of macromolecules in the neonate, in addition to providing a passive immunity, may also serve a protective role by inactivating certain proinflammatory agents, such as PAF.