Polymorphonuclear leukocyte accumulation in inflammatory dermal sites as measured by 51Cr-labeled cells and myeloperoxidase.

Two methods for quantitating polymorphonuclear leukocyte (PMN) accumulation in inflammatory skin lesions were studied. The lesions were produced in rats by intradermal injections of different dilutions of zymosan-activated plasma (ZAP). PMN accumulation in the skin lesions was estimated by determination of (1) homologous 51Cr-labeled PMNs and (2) activity of myeloperoxidase (MPO) in the tissue sample. 125I-labeled human serum albumin was used for measurement of albumin extravasation. The [51Cr]PMN content and MPO activity in the skin lesions were both proportional to the concentration of ZAP injected. The correlation coefficient (r) between the two methods of measuring PMN accumulation in the inflammatory skin lesions was calculated to be 0.81 +/- 0.13 (mean +/- SD, N = 8). The proportionality of the PMN accumulation to the different dilutions of injected ZAP, as measured both by [51Cr]PMN and by MPO activity, and the correlation of the two methods to each other, suggest that these two methods are reliable for measuring PMN accumulation in vivo. The inflammatory reaction also included albumin extravasation, which reached a relatively high level already at the lowest concentration of injected ZAP and did not seem to parallel PMN accumulation.