Kaolin induced a clear and reproducible writhing reaction when intraperitoneally injected into mice. A simultaneous injection (i.p.) of soybean trypsin inhibitor (SBTI) significantly suppressed the kaolin-induced writhing reaction. This writhing reaction was markedly potentiated by a simultaneous injection (i.p.) of captopril. In an in vitro experiment kaolin caused kinin-release in mouse plasma, possibly through the activation of prekallikrein. This activation of plasma prekallikrein and kinin-release were inhibited in the presence of SBTI. Some non-steroidal anti-inflammatory agents inhibited the kaolin-induced writhing reaction dose-dependently. These results suggest that kaolin-induced writhing reaction may be caused by the released bradykinin through activation of the plasma kallikrein-kinin system. This model is a novel and simple tool for assessment of analgesic agents.

Abstract-As previously reported, pretreatment with captopril significantly en hanced pleural exudation of rat carrageenin-induced pleurisy. However, in high molecular weight kininogen-deficient rats (B/N-Katholiek), the pleural exudate volume was significantly less than that of the normal strain (B/N-Kitasato), and captopril pretreatment did not enhance exudation. In the present study, the follow ing additional evidences were demonstrated: 1) Captopril did not increase 6-keto PGF1a level in the deficient strain, but it was significantly increased in the normal strain after captopril treatment; 2) simultaneous administration of soybean trypsin inhibitor with carrageenin markedly suppressed the exudate volume and levels of 6-keto-PGF1a in the normal strain; and 3) indomethacin also suppressed pleural fluid accumulation and the production of arachidonate metabolites. These data suggest that carrageenin causes intrinsic kinin-release through the activation of plasma kallikrein and then in turn, the kinin stimulates the production of arachidonic acid metabolites. Thus these products and kinin may interact to induce more plasma exudation in carrageenin inflammation. The results also indicate that captopril uncovers the effects of bradykinin on exudation and stimulation of arachidonate metabolite production; otherwise, the biological effect of kinin is too slight to produce a clear effect at the initial phase of the inflammation.

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Abstract-Using a bradykinin enzyme immunoassay, we measured the amount of kinin in the peritoneal washings of mice with the kaolin-induced writhing reaction. Simultaneous treatment with captopril, a kininase II inhibitor, significantly increased the kinin level at 1 min after kaolin injection.Soybean trypsin inhibitor injected simultaneously with kaolin almost completely suppressed the kinin level at 1 min with or without treatment of captopril.These results suggest that kinin is released through activation of the plasma kallikrein-kinin system by kaolin, and that kinin could be a main mediator for the writhing reaction.

Nonalcoholic steatohepatitis (NASH) has become a major concern in clinical hepatology. To elucidate the disease mechanisms and to develop a treatment, the advent of an appropriate experimental model is crucial. Pregnant Sprague-Dawley rats were fed a high-fat diet from gestational day 16. Two days after birth, the neonates were injected subcutaneously with streptozotocin (STZ) (180, 200, or 256 mg/kg). The mothers were fed a high-fat diet during the nursing period. After being weaned (4 weeks of age), the juvenile rats were fed the same high-fat diet. The survival rates at the time of weaning were 25.6% (180 mg/kg STZ), 22.8% (200 mg/kg STZ), and 19.4% (256 mg/kg STZ). The mean body weight of NASH rats was approximately 20% less than that of normal rats. Serum levels of glucose, alanine aminotransferase, and hyaluronic acid increased in NASH rats. Histologically, typical features of steatohepatitis such as ballooning, inflammatory cell infiltration, and perivenular and pericellular fibrosis were observed. In an indocyanine green loading test, the blood half-life was significantly longer in NASH rats (5.04 ± 2.14 vs. 2.72 ± 0.72 min; p < 0.05), which was suggestive of an impaired hepatobiliary transportation function. Concomitantly, biliary ICG concentrations in NASH rats stabilized in a delayed fashion compared with normal rats. In addition, the amount of bile excreted in NASH rats was significantly lower than that in normal rats (4.32 ± 0.83 vs. 7.66 ± 1.05 mg/min; p < 0.01). The rat NASH model presented here mimics the clinical features of the disease and will be a helpful tool for medical and bioscience research.