SKIN PLASMA EXUDATION AND VASODILATATION MONITORED BY EXTERNAL DETECTION OF CONVERSION ELECTRONS

We have examined the plasma exudation response of inflammation in guin ea pig skin by a noninvasive method and have evaluated the influence o f vasodilatation. Indium radionuclides have been used to label plasma and blood and conversion electrons have been detected by an external d etector. Transferrin (79,600 Da) was labeled by In-111 or In-113m in v ivo and red blood cells were labeled by In-111 in vitro. These tracers were given to separate groups of anesthetized guinea pigs and baselin e activities were recorded from shaved skin surface areas. Skin prick tests with histamine and saline were performed and time-activity curve s were recorded. The measurements with In-111-transferrin and In-111-l abeled red blood cells demonstrated that histamine produced dose-depen dent accumulation of plasma (up to a 6.5-fold increase) and blood (up to a 2.0-fold increase) in the skin. Hence, about one-third of accumul ation of plasma induced by histamine may be explained by vasodilatatio n. With In-113m-transferrin as plasma tracer greater effects of histam ine were recorded, probably reflecting that the measurements also incl uded deeper sections of the skin. We conclude that the intensity of ac cumulation of plasma in skin inflammation can be monitored by external detection of conversion electrons from In-111- and In-113m-transferri n, and that the influence of vasodilatation can be estimated by detect ion of In-111-labeled red blood cells. (C) 1996 Academic Press, Inc.