Endothelial Nitric Oxide Synthase in Human Intestine Resected for Necrotizing Enterocolitis

Objective

To determine the expression and function of endothelial nitric oxide synthase (eNOS) in submucosal arterioles harvested from human intestine resected for necrotizing enterocolitis (NEC) or congenital bowel disease.

Study design

eNOS expression was determined by using immunohistochemistry. The arteriolar diameter was measured in vitro at pressures of 10 to 40 mm Hg and also in response to the eNOS agonist acetylcholine (ACh), the exogenous nitric oxide (NO) donor S-nitroso-N-acetylpenicillamine, and the smooth muscle relaxant papaverine. Arteriolar release of NO in response to ACh was determined with a Sievers NOAnalyzer. Hemodynamics were also determined at flow rates of 50 and 100 μL/min.

Results

eNOS was present in microvessels from both groups, but NEC arterioles failed to demonstrate physiological evidence of eNOS function: they constricted in response to pressure, failed to dilate or generate NO in response to ACh, and failed to dilate in response to flow. However, they dilated in response to exogenous NO and papaverine, indicating functional vascular smooth muscle and vasodilator reserve.

Conclusion

eNOS-derived NO, a vasodilator in the newborn intestine, did not contribute to vasoregulation in arterioles harvested from intestine resected for NEC. These vessels were constricted; lack of eNOS-derived NO may contribute to this vasoconstriction.

Abbreviations: ACh, Acetylcholine, DSB, Distal small bowel, eNOS, Endothelial nitric oxide synthase, iNOS, Inducible nitric oxide synthase, L-NNA, L-NG-nitro-arginine, NEC, Necrotizing enterocolitis, NO, Nitric oxide, P_i, Inlet pressure, P_o, Outlet pressure, PSB, Proximal small bowel, SNAP, S-nitroso-n-acetylpenicillamine