Site of the Vascular Reponse to Thermal Injury

Abstract

THE increase of vascular permeability in response to a number of types of mild injury—including thermal injury—is biphasic, consisting of a transient immediate phase, usually lasting 20–30 min, and a delayed phase which comes to a maximum several hours later1–3. The alteration of a vessel wall is demonstrable in animals with carbon particles or a vital dye in the circulating blood: in one case the carbon is deposited between the vascular endothelium and the basement membrane under it; in the other, dye-stained plasma exudes into the surrounding tissues. Majno et al.^4,5, applying these methods to the rat cremaster muscle, showed therein that venules and fine capillary vessels were readily distinguishable by their characteristic distribution and size, and that, according to the type of injury, venules alone or both venules and capillaries might be affected. We used Majno's technique to locate the site of vascular change during the response to mild thermal injury. A heated copper disk 9 mm in diameter, as used by Wilhelm and Mason³ in their investigation of thermal injury to the dorsal skin of the rat trunk, was applied to the scrotal skin.