Experimental gingivitis in ODU plaque-susceptible rats. V. The presence of bradykinin in the gingival tissue and the bradykinin inactivating factor in rat dental plaque.

Plaque formation and gingival inflammation were found in ODU plaque-susceptible rats. A study was performed to determine the relationship between the presence of bradykinin in gingival tissue and the inflammatory capacity of rat plaque. Bradykinin content in gingival tissue and the bradykinin inactivating activity of dental plaque of 12-month-old ODU rats were measured. The presence of bradykinin was observed in the gingival tissue of the ODU rat and a bradykinin inactivating factor was found in the rat plaque. The factor was destroyed at 60 degrees C for 30 minutes, at pH 1.5 or by treatment with perchloric acid. The optimum pH of the factor was approximately 8.0. Chelate reagents, such as O-phenanthroline and EDTA . 4Na, strongly inhibited the bradykinin inactivating factor. The protease inhibitor, Trasylol, also inhibited this factor. The SH reagent, L-cysteine, inhibited weakly and Zn++ inhibited less. The investigation suggested that the rat plaque posseses the ability to inactivate bradykinin and plays an important role in modifying the inflammatory response caused by bradykinin in gingival tissue.