Inflammatory reaction in an experimental model of open wounds in the rat. The role of polymorphonuclear leukocytes.
The accumulation of polymorphonuclear leukocytes (PMNLs) and the concentration of prostaglandin E2 in full thickness open skin wounds, created in the back of the rat, were studied. The quantity of PMNLs in the granulation tissue, assessed by analysis of wound exudate myeloperoxidase activity, increased from 0.45 units/ml on day 1 after wounding to 0.8 units/ml on day 2 and then remained constant throughout the 5 days of observation. The prostaglandin E2 concentration in wound exudate was measured by radioimmunoassay increased progressively from 70 ng/ml on day 1 to 290 ng/ml on day 5. The lack of correlation between these two variables indicates that PMNLs were not the major source of prostaglandin E2. To study the relation between PMNL accumulation, blood flow, and albumin extravasation in the granulation tissue, rats were treated with an antineutrophil serum. This resulted in an 83% decrease in circulating PMNLs and a 61% decrease in granulation tissue myeloperoxidase activity on the 5th day, as compared with rats treated with normal rabbit serum. No relationship was observed between myeloperoxidase activity and blood flow (r = 0.37) or between myeloperoxidase activity and albumin extravasation (r = -0.34) when absolute values were compared. However, when interindividual variation in the absolute levels of the variable measured was eliminated, by calculating in each rat a left to right wound ratio, good correlations (r = 0.81 and r = 0.65, respectively) were found. It is suggested that blood flow and albumin extravasation in the granulation tissue are influenced by local PMNL accumulation.