A model of intestinal ischemia in the neonatal rat utilizing superior mesenteric artery occlusion and intraluminal platelet-activating factor

The human premature newborn is susceptible to necrotizing enterocolitis (NEC) in the first 1 to 3 weeks of life, a time when the gastrointestinal tract is structurally and functionally premature. Studies of NEC are hampered by the lack of a standard, reproducible model in newborn animals. The purpose of this study was to produce a model for intestinal ischemic injury in newborn rats. On Days 14, 18, 22, and 26 of life, newborn rats (10/day) were subjected to 1 hr of superior mesenteric artery occlusion with a microaneurysm clip. Platelet activating factor (PAF, 50 micrograms/kg) was injected into the lumen of the proximal small intestine after occlusion was initiated. Control animals (10/day) underwent sham laparotomy on Days 14, 18, 22, and 26. Animals were autopsied upon demise (7.6 +/- 0.7 hr) or at 24 hr. The intestine was inspected for gross ischemic changes and samples were taken for histology and myeloperoxidase (MPO, an index of neutrophil infiltration). Ischemic injury was graded in a blinded fashion, by a pathologist, using a scale from 0 to 4 (0, no injury; 4, full-thickness necrosis). All animals in the experimental groups had evidence of histologic injury (mean +/- SEM) on Days 14 (1.0 +/- 0.0), 18 (2.5 +/- 0.5), 22 (3.6 +/- 0.3), and 26 (3.1 +/- 0.5). The sham-operated control animals had no injury (P < 0.0001). MPO levels (U/g protein) on Days 18 (27.2 +/- 1.7 vs 13.9 +/- 2.3), 22 (40.9 +/- 5.4 vs 7.6 +/- 0.8), and 26 (29.3 +/- 4.4 vs 7.6 +/- 1.0) were significantly higher in experimental groups vs controls (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)