Decrease in peritoneal mast cell count in rats with adjuvant arthritis. II. Inhibition by anti-inflammatory and immunosuppressive drugs.

The following drugs were administered daily to adjuvant-injected rats: indomethacin, flufenamic acid, phenylbutazone, prednisolone, dexamethasone, methotrexate and 6-mercaptopurine. The effects on the decrease in the mast-cell count and histamine content of the peritoneal fluid were studied as well as the effect on the development of polyarthritis 14 days after adjuvant injection. At the doses tested, these drugs markedly inhibited changes in the parameters of peritoneal fluid. With the exception of flufenamic acid, the preventive effects on the decrease in the peritoneal mast-cell count paralleled the prevention of development of arthritic lesions. 6-Mercaptopurine administered daily for 5 consecutive days starting from day 0 was almost as effective as when it was given over the entire period (days 0 through 13). These results show that the decrease in the peritoneal mast-cell count is one of the symptoms of adjuvant disease in rats that can be used for the quantitative evaluation of antirheumatic drugs.