Pharmacological studies of N-(2-mercapto-2-methylpropanoyl)-L-cysteine (SA96) (3). Effects of SA96 on experimental allergic reactions.

The effects of an antirheumatic agent, N-(2-mercapto-2-methylpropanoyl)-L-cysteine (SA96), were investigated on allergic reactions in rats and guinea pigs. The effects of SA96 were compared with those of D-penicillamine (D-Pc). SA96 given twice orally at the doses of 10 to 50 mg/kg significantly caused inhibitions of 28%, 29% and 44% against passive cutaneous anaphylaxis (PCA), reversed cutaneous anaphylaxis (RCA) and reversed passive Arthus (RPA) reactions, which are classified as Type I, Type II and Type III allergic reactions, respectively. D-Pc also showed inhibitions of 30%, 23% and 18% on Type I, Type II and Type III reactions, respectively, and inhibitions on Type II and Type III reactions were not significant. On the other hand, SA96 (10 to 50 mg/kg twice) had no influence on the Type IV allergic reaction, delayed hypersensitivity, while D-Pc (20 mg/kg twice) showed an enhancement of 27% on the Type IV reaction. In the in vitro study, SA96 inhibited the hemolytic complement activity at 10(-4) to 10(-2) M and the macrophage migration at 1 X 10(-4) to 5 X 10(-3) M in a dose-dependent manner. These in vitro activities of SA96 were more potent than those of D-Pc. These results showed that SA96 had some different immunopharmacological properties on experimental allergic reactions as compared with those of D-Pc.