Phospholipase A2 (PLA2) regulates the production of platelet-activating factor (PAF), a phospholipid inflammatory mediator which may be important in the pathogenesis of necrotizing enterocolitis (NEC). We have developed a newborn rat model of NEC induced by asphyxia (A) and formula feedings (F). In this model, the clinical signs and intestinal lesions are similar to those of human NEC. This experiment measured intestinal PLA2 enzyme activity and PLA2 gene transcription in the rat model of NEC. Intestinal PLA2 enzyme activity from 14 formula-fed and asphyxiated(F,A) and 13 non-asphyxiated, mother-fed control rat pups was assayed by measuring the conversion of a radiolabeled phosphatidylethanolamine substrate to free arachidonic acid. The mean PLA2 enzyme activity for the stressed animals compared to the control pups was 90.6 ± 10.6 vs 58.7± 7.7 pmol/gm protein/hr (p=0.02). Intestinal PLA2-II mRNA was quantified by competitive RT-PCR using a 401bp cRNA of rat PLA2-II(gift of Dr. W. Hsueh). Following the competitive RT-PCR amplification, reaction products were separated by electrophoresis and transcript and competitor cDNA bands quantified by phosphorimaging. Intestinal samples were studied from 5 starved (S), 6 formula-fed (F) and 14 formula-fed and asphyxiated (F,A) newborn rats. Mean PLA2 transcript levels (pg PLA2 transcript per ug total RNA) were similar between the starved and formula-fed groups (0.366 ± 0.259 vs 0.260 ± 0.052) but increased more than 5-fold in the formula-fed rat pups subjected to asphyxia(0.260 ± 0.052 vs 1.399 ± 0.427). These data suggest that in the newborn rat model of NEC these stresses increase PLA2 enzyme synthesis at the level of gene transcription and that the increased PLA2 enzyme activity may represent an increase in PLA2 -II gene activity. The increased PLA2 enzyme activity following exposure to risk factors for human NEC further supports the role of PAF in the pathogenesis of NEC. Supported by NIH grant HD 00999 and a grant from The March of Dimes.