met-enkephalin decreases in adjuvant arthritic ankles

Objective. To study whether met-enkephalin (met-enk) concentration changes in adjuvant arthritic ankles and spinal cords. Methods, Adjuvant arthritis was induced by intradermal injection of Mycobacterium butyricum in paraffin oil, into the base of rat tail. The levels of met-enk were measured using radioimmunoassay and high performance liquid chromatography electrochemical detection in arthritic ankle and spinal cord of arthritic and control rats. Protein concentration was measured according to Lowry method. Results. We observed a significant decrease of concentration of met-enk in ankle joints of chronic arthritic rats. However, increased concentration of met-enk was obtained in the spinal cord of chronic arthritic rats. Conclusion. The significant reduction of met-enk concentration in the arthritic ankle joints indicates a possible role for the endogenous opioid peptide in arthritis.