Studies on Induction of Salivary Cysteine Proteinase Inhibitor by Isoproterenol

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Rat cystain S(RSC), a cysteine proteinase inhibitor belonging to family 2 of the cystatin superfamily. (1)Papain(Ki : O. l nM)and ficin(Kl : 0.2 nM)were inhibited strongly, and bromelain and cathepsin C partially. The proteinases were inhibited by RSC competitively. However, trypsin, kalllkrein and pepsin did not inhibit by RSC. (2)When RSC was reduced and S-carboxymethylated, the proteinases inhibitory activity was lost completly. Complex formation between papain and RSC was 1 : 1 molar ratio. (3)The proteinase inhibitory activity of RSC was stable to extremes of pH 1-12 for I hour at 37 ﾟC) and to heat treatment (100 ﾟC for 1 hour). (4)Cysteine proteinases are important in the penetration of human tissue by microorganism. Anti-bacteria activity of RSC was tested to seventeen strains including of oral bacteriaby disc diffusion analysis. We found that RSC have anti-bacterial activity against Bacteroides gingivalis, an oral bacterium suspected of being a pathogen of periodontal disease(minimum effective dose : 75 mug/disc). (5)Treatment of rats with the beta-adrenergic-agonist, isoproterenol, produces hypertrophy and hyperplasia of submandibular glands and induces a large quantity of RSC. However, biological rule of the responses did not understand. When papain, a cysteine proteinase of plant(papaya), was administered into the oral cavity of rats of 8 weeks age, a dramatic increase in the level of RSC in enlarged submandibular glands. The magnitude of induction of RSC and enlargement of the glands were correlated with the dose of papain and duration of the treatment. We tested to specify on the respence in kind of proteinase. We found that ficin, a cysteine proteinase of plant(Ficus), and trypsin, a serine proteinase of pancreas, had same activity. We proposed that induction of the RSC in the submandibular glands by oral administration of the proteinases is a biological response which plays a role in preventing injury exgeneous proteinases.