P0936 INTESTINAL PLATELET-ACTIVATING FACTOR ACETYLHYDROLASE ACTIVITY IN A NEONATAL PIGLET MODEL OF NECROTISING ENTEROCOLITIS.

Abstract

Introduction: We recently reported a model of necrotising enterocolitis (NEC) in the neonatal piglet using hypoxia (H) and endotoxin (lipopolysaccharide, LPS), which both induce endogenous release of platelet-activating factor (PAF). Intestinal lesions produced in this model are ameliorated by a prophylactic PAF-antagonist, suggesting a role for PAF in the pathogenesis of NEC.1 PAF is rapidly degraded in-vivo by the specific enzyme PAF-acetylhydrolase (PAF-AH). The aim of this study was to determine PAF-acetylhydrolase activity throughout the intestine in this model of NEC. Methods: 9 anaesthetised neonatal piglets were studied: controls n=2; hypoxia + low dose LPS [H+LLPS] n=3; and hypoxia + high dose LPS [H+HLPS] n=4. Control animals breathed room air; H+LLPS animals received a combination of 10% O2 (for 45 minutes) and LPS (2 mg/kg); and the H+HLPS animals received 10% O2 and LPS (4 mg/kg). The experiment was terminated after 360 minutes and samples of intestine were snap-frozen and stored at −80 degrees C. Cytosolic PAF-AH activity was determined in the duodenum, jejunum, proximal ileum, distal ileum, caecum and colon with a colourmetric assay using 2-Thio-PAF as a substrate. Results: In control animals PAF-AH activity was lowest in the duodenum and increased along the intestine to a maximum in the ileum (between 5 and 7 fold) and was decreased in the colon. A similar pattern of enzyme activity was observed in both insult groups. In the H+LLPS animals there was no statistically significant change in the mean PAF-AH activity in any region when compared with controls. However, in the H+HLPS animals the mean PAF-AH activity was significantly increased (between 3.5 and 11 fold) in all regions when compared with controls (p < 0.05). Conclusion: In all groups PAF-AH activity increases between 5 and 7 fold from the duodenum to the distal ileum before decreasing in the colon. In addition, hypoxia and high dose LPS resulted in a significant rise in PAF-AH activity from the baseline levels seen in controls. In our model, these insults cause intestinal damage typical of NEC. The rise in PAF-AH activity may be in response to a rise in PAF in these areas.