Effects of selected inflammatory mediators on blood flow and vascular permeability in the dental pulp

One of the major events involving inflammatory processes is the alteration of microcirculatory hemodynamics by inflammatory mediators released from tissue components. Using modern macrocirculatory techniques, 15 mu radioisotope labeled microspheres, 133Xe washout, laser Doppler flowmetry and double isotopes, 125 and 131I-albumin, and microcirculatory methods, intravital fluorescence microscopy with FITC labeled dextran, we have examined the effects of selected mediators, e.g. 5-hydroxytryptamine (5-HT), prostaglandin E2 (PG-E2), bradykinin (BK), substance P (SP), calcitonin gene related peptide (CGRP) and histamine on blood flow and vascular permeability in the pulp of experimental animals. Surprisingly, SP and CGRP caused weak albumin leakage in the pulp, while the opposite is true in high compliance tissues, such as muscles, suggesting that the vessels in a low compliance environment, such as the pulp, may not be as permeable in response to selected mediators. Intraarterial injection of 5-HT caused a strong vasoconstriction which was mediated by 5-HT1p receptor subtype. The pulpal 5-HT receptor subtype was identified by immunocytochemistry, receptor autoradiography and functional investigations. Intravital fluorescence microscopy observations of the rat incisor preparation showed that histamine, BK and PGE2 increased permeability, whereas isoproteranol caused partial inhibition of the BK-induced increase. In an induced pulpal inflammation model using plaque extract, blood flow increased over 40% in the moderately inflamed pulp, which demonstrated severe vasodilation and polymorpholeukocyte accumulation. In the partially necrotic pulp, blood flow decreased nearly 35%. Results of this study clearly show that there is a high structural/functional correlation in pulpal microcirculation in inflammation. As demonstrated in this presentation, the effects of inflammatory mediators on pulpal microcirculatory hemodynamics are complex.(ABSTRACT TRUNCATED AT 250 WORDS)