Assessment of Antiinflammatory Agents Using 125I-Labeled Human Serum Albumin to Quantify Footpad Edema Volume in the Rat

Intravenously injected human serum albumin, labeled with radioactive iodine ([125I]HSA), accumulates at inflammatory foci in proportion to the volume of the exudate, making it possible to quantify the volume of edema. This paper describes the use of [125I]HSA to measure edema formation in the carrageenin rat-footpad model, both continuously and at a single time point. In assessing antiinflammatory agents, the method was shown to be more sensitive than the most commonly used technique of thickness measurement. Because anesthetics are known to suppress inflammation, the comparative effect of five anesthetic agents on the inflammatory response was determined. Ether was the only anesthetic tested that did not substantially inhibit the accumulation of edema. The technique overcomes many of the limitations of previously used procedures and has the potential to become the method of choice when assessing edema in the rat footpad.