A rapid method of monitoring the acute phase response in a rat model

The acute phase response (APR) is accompanied by major changes in micronutrient status. It is important to be able to quantitate the degree of APR, which can then be related to the accompanying alterations in micronutrient levels. A rapid and convenient means of achieving this, viz. the use of an animal model in which APR can be induced, would facilitate such an investigation. The aim of the present study was to establish, by means of a rat model, a rapid procedure to identify APR which is less time-consuming and less expensive than the more traditional enzyme-linked immunosorbent assay and radio-immunoassay. Blood was drawn immediately prior to, and at 24, 48, 72 and 96-hour intervals post-inducement of the acute phase. The serum was deproteinised and treated with a dye, Auramine O, which specifically binds the acute phase protein alpha 1-acid glycoprotein (AAG), the latter remaining in solution after deproteinisation. The product formed is a fluorescent addition compound. With fluorescence spectrophotometry, levels of AAG were determined and the extent of APR monitored. A progressive and reproducible increase in AAG was observed, the highest fluorescence intensity recorded after 48 hours; this indicated a mean value (N = 5) of 9.4 mg/ml from zero at baseline. With a spiking approach, a mean AAG recovery of 96% was obtained. The validated methodology, less expensive and less time-consuming than existing procedures, which rapidly detects AAG in rat serum, provides a simple technique for monitoring the APR process in these animals.