TREATMENT OF ANTIGEN-INDUCED ARTHRITIS IN RABBITS BY THE INTRAARTICULAR INJECTION OF METHYLPREDNISOLONE, Y-90 OR CHLORAMBUCIL

Rabbits with a bilateral antigen-induced arthritis were injected intra -articularly (i.a.) in one joint with methylprednisolone (1 mg), Y-90 (18.5 M Bq) or chlorambucil (1 mg) as a single dose. The severity of a rthritis was determined by measuring joint swelling and skin surface t emperature, macroscopic and histological changes in the joint being as sessed 8 weeks after induction of arthritis when the rabbits were kill ed. Methylprednisolone injected at the time of antigen challenge or 3 weeks later caused a reduction in joint swelling and temperature (P<0. 05) for 1 to 6 weeks after injection. Y-90 had an initial pro-inflamma tory effect lasting several days, but later caused a modest reduction in joint swelling for up to 4 weeks (P<0.05). Eight weeks after induct ion of arthritis, neither methylprednisolone nor Y-90-treated joints s howed any significant reduction in erosion or histopathology compared with control arthritic joints. Chlorambucil injected 1 week after anti gen challenge caused a rapid reduction in joint swelling which was mai ntained for the duration of the study. Joint surface temperature was r educed to a lesser extent. Eight weeks after induction of arthritis, c hlorambucil-treated joints showed a decrease (P<0.05) in all of the pa rameters of disease pathology assessed. Treatment with chlorambucil in tra-articularly was clearly more effective than with methylprednisolon e of Y-90 at the doses employed and deserves further study is a potent ial treatment for chronic synovitis.