0629 Involvement of Nitric Oxide in Regulation of Gingival Circulation
Y. OMORI, Kanagawa Dental College, Yokosuka, Japan

Objective: Reactive hyperemia is a rational response that regulates the local circulation of the tissue after ischemia, and improves oxygen supply to the tissue. The aim of this study is to examine a possible involvement of nitric oxide (.NO) in reactive hyperemia of the canine gingiva induced by tissue compression. Methods: Female beagle dogs weighing 8-10 kg were anesthetized with sodium pentobarbital (25 mg/kg, i.v.). Blood flow and tissue PO2 of the gingiva, and the systemic hemodynamics were continuously monitored during compression-induced hyperemia. Reactive hyperemia was elicited by releasing the transient compression of the right mandibular gingiva. In order to perform pharmacological assessment of reactive hyperemia, various drugs were injected into the external carotid artery. Direct detection of .NO concentration was tried using an .NO-selective electrode. Distribution of .NO synthase (NOS) activities in the gingival region were visualized by NADPH-diaphorase histochemistry. Results: A transient compression of the gingiva resulted in an immediate decrease in the tissue blood flow and PO2. Upon releasing the pressure, an increase in the blood flow and a recovery of the tissue PO2 were observed in an ischemic interval-dependent manner. These hyperemic responses were not significantly altered by pretreatment with muscariic antagonist, b-blocker, H1, H2-blocker. Whereas, pretreatment with L-NAME (60 mg/kg, i.a.), an inhibitor of NOS, significantly suppressed the reactive hyperemia. Furthermore, we could detect an increase of .NO concentration by using the .NO-selective electrode in the gingival tissue during a reactive hyperemia. NOS activity was localized in endothelia, and perivascular nerve fivers in post-hyperemic gingival tissue. Conclusion: These results have suggested a possibility that .NO is involved in reactive vasodilation that underlies the compression-induced hyperemia of the gingiva, and plays a major role in the maintenance of homeostasis in the gingival circulation.

Seq #71 - Oral Tissues, Pharmacology
11:00 AM-12:15 PM, Thursday, 26 June 2003 Svenska Massan Exhibition Hall B

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