Role of leukocyte accumulation and oxygen radicals in ischemia-reperfusion-induced injury in skeletal muscle

The role of leukocytes and nonleukocyte-derived reactive oxygen metabolites (ROMs) in reperfusion-induced skeletal muscle injury was determined. Male rats received 2 h no-flow hindlimb ischemia-reperfusion (I/R, n = 6) or wer e rendered neutropenic via antineutrophil serum (ANS) before I/R (I/R + ANS , n = 5). Oxygen radicals in the absence of neutrophils were tested by admi nistration of dimethylthiourea (DMTU) (I/R + ANS + DMTU, n = 5). Perfused c apillaries (CDper) and rolling (L-r), adherent (L-a), and extravasated leuk ocytes (L-e) in the extensor digitorum longus muscle were measured every 15 min during 90 min of reperfusion using intravital microscopy. The vital dy es bisbenzimide (BB) and ethidium bromide (EB) provided direct measures of tissue injury (EB/BB). CDper decreased immediately on reperfusion in the I/ R and I/R + ANS groups. CDper in the I/R + ANS + DMTU group remained at bas eline throughout reperfusion. L-a increased in the I/R group; however, EB/B B was the same between I/R and I/R + ANS groups. Injury in the I/R + ANS DMTU group did not differ from other groups greater than or equal to 60 min , after which EB/BB became significantly lower. L-e did not differ between groups and was highly correlated to tissue injury. The results suggest that L-e lead to parenchymal injury, and ROMs lead to perfusion deficits during the early reperfusion period after ischemia.