Abstract
We have previously reported that an increase of the opioid petide content in the rat incisor pulp induced by cavity formation was markedly inhibited following infusion of Des-Arg9- [Leu8] -bradykinin, a potent bradykinin (BK) -antagonist, into the pulp cavity and the inhibitory effect of BK-antagonist was reversed by combination with BK. These findings suggested that BK might be a triggerr in the increase of the pulpal opioid peptide content. In the present study, we examined the BK-effect on the opioid peptide content in in vitro experimental system newly designed by us, using whole incisor pulp of the rat, in order to certify this suggestion. The met-enkephalin (ME) -like peptide content was remarkably increased by BK at a concentration of 1μM, but not in higher concentrations. The effect of BK (1μM) was antagonized with Des-Arg9- [Leu8] -BK (1μM) and was not inhibited by FOY-305 (0.001μM), a trypsin inhibitor. From these results, it was demonstrated that the increase of ME-like peptide content induced by BK was due to activation of an enzyme different from trypsin-like enzyme which was mediated through BK-receptor in the pulp.
