Hyperthermia-induced changes in the vascular permeability of rats: a model system to examine therapeutic interventions.

Extravasation in the heart, liver, lung, kidney, spleen, gastrocnemius, and duodenum was quantified in normothermic and hyperthermic (core temperature (T(c))=41.5, 42, or 42.6 degrees C) rats. Following attainment of the target T(c), Evans blue (Eb) was administered via jugular cannula; the animals were anesthetized, exsanguinated, tissues removed and washed in saline, and Eb extracted with formamide. There was significantly (p<0.05) more Eb (µg/g of dry wt of tissue, mean+/-SD) in the tissues of severely hyperthermic (T(c)=42.6 degrees C) rats vs that of control rats: liver - 198+/-39 vs 125+/-28, kidney - 376+/-68 vs 176+/-60, and small intestine - 170+/-49 vs 106+/-20. This model may be useful in evaluating the efficacy of treatment modalities designed to sustain vascular integrity in the face of environmental insult.