Abstracts
1999 Digestive Disease Week

# 3475 EXPRESSION AND FUNCTION OF INDUCIBLE NITRIC OXIDE SYNTHASE DURING RAT COLON ANASTOMOTIC HEALING
D T Efron, F J Thornton, C Steulten, U S Tantry, M B Witte, T Kiyama, Adrian Barbul, Sinai Hosp of Baltimore, Baltimore, MD

Nitric oxide (NO) plays a significant but incompletely understood role in fibroblast proliferation and cutaneous wound collagen synthesis; however, the participation of inducible nitric oxide synthase (iNOS) in gastro-intestinal anastomotic healing has not been studied. Male Sprague-Dawley rats underwent single layer left colonic anastomosis. Animals were sacrificed at 24 hour intervals post-operatively and the anastomosis was excised; uninjured colon was taken from unoperated controls. Anastomotic and uninjured colon tissue samples were analyzed as follows. RT-PCR confirmed absence of iNOS mRNA in control colon and expression of the gene in anastomotic tissue on all study days. Northern hybridization demonstrated maximal iNOS mRNA transcription on day 1 with decreased levels on days 3 and 5. iNOS enzyme activity, measured biochemically by the conversion of [3H]arginine to [3H]citrulline ex-vivo, was also maximal on day 1 (7.35 ± 1.34 pmol/mg protein/min (± SEM), n=10) and decreased on days 3 (4.37 ± 2.32, n=6) and 5 (2.80 ± 0.92, n=6). Immunohistochemical staining demonstrated that iNOS expression is confined to a discrete cell population in the region of the anastomosis containing inflammatory cells, that those cells assume a highly conserved position on the luminal edge of the proliferating scar and are present through the fibroplastic phase of healing. 5 day old anastomoses from rats treated with a continuous iv infusion of S-methylisothiourea (a selective inhibitor of iNOS) at a dose of 200mg/kg/day demonstrated a significantly reduced anastomotic bursting pressure when compared to rats treated with iv normal saline (113.8 ± 4.7 vs 170.5 ± 17.0 mmHg, p<0.05) These results suggest that iNOS gene expression is induced during colonic anastomotic healing, that iNOS activity is present through all phases of healing but is maximal through the inflammatory phase, and that iNOS function is required for optimal anastomotic healing.

Copyright 1996 - 1999, SSAT, Inc.