Chondrocytic monoamine oxidase activity in the development of natural murine osteoarthritis.

Most of the male STR/ORT mice develop osteoarthritis (OA) involving the medial tibial plateau. A peculiarity of two chondroprotective drugs is the presence of a nitrogen atom so that cleavage of the molecule could generate a molecule that might act as an inhibitor of monoamine oxidase (MAO). Direct examination showed abnormal localization of MAO in the potentially osteoarthritic cartilage indicating possible abnormal response to catecholamines. In normal cartilage, the direct effect of excessive concentration of adrenaline caused considerable oedema, as measured by microscopic interferometry. It is therefore suggested that the excess of water found in the matrix of osteoarthritic cartilage may be related to disturbance of the MAO activity.