Abstracts
2000 Digestive Disease Week

# 2227 Modulation of Growth Factor Expression by Nitric Oxide During Rat Colon Anastomotic Healing.
David T. Efron, Daniel Most, Udaya S. Tantry, Hanping Shi, Adrian Barbul, Baltimore, MD

We have previously shown that inhibition of nitric oxide generated by inducible nitric oxide synthase (iNOS) results in impaired colon anastomotic healing. We studied whether disruption of iNOS activity would alter the normal pattern of growth factor expression during anastomotic healing. Twenty-two male Sprague-Dawley rats underwent distal colonic division and anastomosis and jugular venous catheterization. Rats were randomized into two groups. The first group (n=10) received q8 hour intravenous injections of 10mg/kg L-N-Iminoethyl-Lysine (L-NIL, a selective inhibitor of iNOS), while the second group (n=12) received q8 hour saline (equal volumes). On post-operative day 5, animals were sacrificed. Anastomotic bursting pressure was determined and plasma nitrite/nitrate (NOx) concentration was measured as an index of iNOS inhibition. Histologic sections of the anastomosis were subjected to in situ hybridization versus mRNA of the proteins in the table below. Positive control was achieved using a poly-T probe versus ubiquitous mRNA poly-A tails. Positively stained cells were quantified using a calibrated optical grid encompassing 0.5mm2 area centered over the anastomosis. Results are reported as the number of positive cells/ 1000 cells positive for poly-T. Statistical significance was determined by the Students’ t-test. L-NIL treated animals demonstrated a 32% decrease in plasma NOx as compared to controls (24.3 ± 2.5 vs. 35.6 ± 2.2 mM, mean ± SEM; p<0.05,). This corresponded to a 15% decrease in anastomotic bursting pressure (152.6 ± 4.4 vs. 179.0 ± 9.6 mmHg mean ± SEM;p<0.05). L-NIL also markedly increased the number of cells expressing TGFb, TNFa, VEGF, iNOS, and eNOS, but had no effect on bFGF expression. The data demonstrate that iNOS inhibition markedly disrupts the profile of cytokine and growth factor mRNA normally expressed during anastomotic healing. This provides in vivo evidence that NO modulates gene expression during anastomotic healing.