NITRIC-OXIDE REGULATES WOUND-HEALING

Nitric oxide (NO) synthesis occurs during wound healing, but its role has not been defined. To study the effect of NO on wound repair, S-met hyl isothiouronium (MITU, a competitive inhibitor of NO synthase) was administered at a dose of 10, 50, and 100 mg/kg body weight/day, using intraperitoneally implanted miniosmotic pumps. Groups of 10 male Balb /C mice underwent a dorsal skin incision and polyvinyl alcohol sponges were inserted subcutaneously. The animals were sacrificed 10 days pos twounding and wound breaking strength and hydroxyproline content of sp onges, an index of reparative collagen deposition, were determined. So me sponges were used to harvest wound fluid and infiltrating cells, wh ich were then incubated overnight with or without 1 mM MITU. Nitrite a nd nitrate, stable end products of NO, were measured in wound fluid an d in wound cell culture supernatants. Continuous intraperitoneal infus ion of MITU significantly decreased wound fluid nitrite/nitrate concen trations in a dose dependent manner (P < 0.01), Inhibition of wound NO synthesis by 100 mg MITU/kg/day was paralleled by lowered wound colla gen accumulation (P < 0.01) and wound breaking strength (P < 0.01). In vitro NO synthesis by wound cells obtained from animals treated with 100 mg MITU/kg/day was not significantly different from controls (12.6 +/- 1.2 vs 10.7 +/- 0.6 nmole NO2 + NO3/mu g DNA), reflecting the rev ersible inhibition of NO synthase by MITU. However, NO production was equally inhibited in wound infiltrating cells by the in vitro addition of MITU (83% vs 85%, respectively). These data suggest that nitric ox ide synthesis is critical to wound collagen accumulation and acquisiti on of mechanical strength. (C) 1996 Academic Press, Inc.