2．6150 Experimental gastric ulcer in the rabbit
Karsner et al. 1) attempted to induce a Shwartzman reaction in the rabbit stomach using a standard surgical procedure. However, the reaction was weak because it was induced intradermally and thus did not produce gastric ulcer. Here, we succeeded in producing typical gastric ulcer in the rabbit via a Shwartzman reaction and herein describes the procedure.
Procedure and results
To induce a Shwartzman reaction in subcutaneous tissue and preferred sites in organs, it was considered necessary to use an adjuvant in the preparatory injection and to administer the intravenous endotoxin before administering the local injection; a procedure contrary to the standard procedure for inducing a Shwartzman reaction 2). This was done, however, to avoid the Gross-Ogata effect which is caused by the absorption of a trace amount of endotoxin from the preparatory injection site into the vasculature.
Purified endotoxin mixed with Freund's adjuvant was intradermally injected into rabbits as the preparatory injection. After 24 h, the eliciting injection was performed using the standard procedure, resulting in a negative Shwartzman reaction. We then attempted to subcutaneously induce a Shwartzman reaction in rabbits using purified endotoxin mixed with gelatin, gum arabic, soluble starch, 1% aqueous solution of carboxymethylcellulose, or 0.1% aqueous solution of agar as an adjuvant, using the standard or contrary procedure for a Shwartzman reaction; however, neither procedure induced a reaction of sufficient strength. Unexpectedly, local injection of bacteria killed at 60 °C for 30 min induced a stronger subcutaneous reaction than that of purified endotoxin with adjuvant. This indicated that killed bacteria have endotoxic activity and produce an adjuvant effect.
Rabbits were laparotomized under general anesthesia, and 0.25 ml of saline suspension of killed E. coli bacteria (2 mg/ml) was precisely injected through the serous membrane into the musculosubmucosa of the stomach with a fine needle. After 24 h, 50 γ of purified endotoxin was intravenously administered following the standard procedure for a Shwartzman reaction. The procedure was repeated except with systemic injection being performed before local injection.
In the rabbits in which killed bacteria were injected into the gastric musculosubmucosa and after 24 h purified endotoxin was intravenously injected following the standard procedure, laparotomy performed 24 h post-procedure revealed hemorrhagic necrosis at local injection sites. One-third of these rabbits had microscopically and histologically typical gastric ulcer. Furthermore, edema, hemorrhage, and fibrinoid degeneration were extensively observed. Hyalinization of muscularis mucosae and cellular infiltration into the muscle layer and serous membrane were also observed. The largest ulcer was 8 mm in diameter. Neither the radiation pattern of gastric folds nor perforation/penetration to the serous membrane was observed in any rabbit. The same results were obtained when performing systemic injection before local injection. Killed bacteria were also injected under the serous membrane using the same procedure, but did not produce hemorrhage or ulcer. When purified endotoxin, instead of bacteria, was mixed with the aforementioned water-soluble materials and injected into the gastric musculosubmucosa using the same procedure, hemorrhage but not ulcer was produced. Local injection alone without intravenous injection did not produce any major macroscopic lesion. On the basis of these findings, it is hypothesized that some types of human gastric ulcer arise within a short time in response to allergic reaction.
This abstract was presented at the 11th Bacterial Toxin Symposium and at the 14th Annual Meeting of Japanese Society of Allergology.
The author would like to thank Dr. Yamanaka for reviewing this manuscript and Drs. Hosokawa and Yamashita of Yamaguchi Medical College (currently Yamaguchi University School of Medicine) for their assistance preparing tissue specimens.
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