The effect of salicylate and chloroquine on prostaglandin-induced articular damage in the rabbit knee.

Prostaglandins are found in increased concentrations in various arthritic joint fluids, and the E and F series have been shown to produce inflammation. Vane suggests that the effectiveness of aspirin is mediated by inhibition of synthesis or release of prostaglandins. In our studies PGE-1 intra-articularly produced the greatest amount of synovial and cartilage damage of the several PGs tested. Five knee intra-articular injections of 500 ng PGE-1 were given to 12 mature white New Zealand rabbits at 4 day intervals, with control solutions on the opposite sides. Four with intramuscular chloroquine at clinical levels and 4 controls. At 20 days histologic examination with H & E and safranin-O showed increased synovitis and abnormal cartilage in the controls and salicylate groups, normal cartilage in the chloroquine group. Whereas chloroquine's ability to stabilize cell membranes is protective in this experiment, salicylate's ability to prevent biosynthesis of prostaglandins is bypassed and therefore is not protective. Vane's hypothesis is supported by this study of PG induced experimental arthritis.