DIRECT EVIDENCE FOR THE OCCURRENCE OF SUPEROXIDE RADICALS IN THE SMALL-INTESTINE OF THE BURNED RAT

To determine if superoxide radicals (0(2)-) and related metabolites ar e generated in extradermal tissues of burned animals, 2-methyl-6-[p-me thoxyphenyl]-3,7-dihydroimidazol [1,2-a]pyrazin-3-one (MCLA) was infus ed intravenously into rats, and change in the chemiluminescence (CL) i ntensity of the small intestine was determined by using a sensitive ph otodetector. When animals were challenged with burn stress of 40% tota l body surface area (TBSA), the CL intensity of the intestine graduall y increased, reaching a maximum within 1 hour and remaining elevated f or up to 3 hours. Pretreatment of animals with a long-acting superoxid e dismutase (SOD) derivative (SM-SOD) significantly inhibited the incr ease in CL intensity. Administration of SM-SOD immediately after induc ing burn injury also significantly inhibited the increase in CL. These results suggest that superoxide radicals are generated in extradermal tissues, such as the small intestine, in the early stage after burn i njury.