Characterization of a local renin-angiotensin system in rat gingival tissue

There is paucity of data regarding the unequivocal existence of crucial renin-angiotensin system (RAS) components, such as renin and angiotensinogen, in the rat gingival tissue. Additionally, so far there is no information on the expression and contribution of enzymatic pathways to angiotensin (Ang) II generation in this tissue. Objectives: The aims of this work were to 1) study the expression and localization of RAS components to the rat gingival tissue and 2) evaluate the in vitro production of Ang II and other peptides by rat gingival tissue homogenates. Methods: In the rat gingival tissue mRNA expression was assessed by reverse transcription-polymerase chain reaction (RT-PCR) and protein was detected by immunohistochemical (IHC) analysis. A standardized fluorimetric method with the tripeptide Hip-His-Leu was used to measure tissue ACE activity in rat gingival tissue homogenates. High performance liquid chromatography (HLPC) was used to analyze the products formed after the incubation of rat gingival tissue homogenates with Ang I, Ang II or tetradecapeptide renin substrate (TDP). Results: RT-PCR revealed the expression of mRNA for renin, angiotensinogen, ACE and Ang II receptors (AT1a, AT1b and AT2). ACE activity was detected by the fluorimetric assay. When Ang I was used as the substrate, HPLC analyses showed the formation of Ang II, Ang 1-9 and Ang 1-7 whereas these same peptides and Ang I were formed when TDP was the substrate. Additionally, HPLC revealed absence of Ang II degrading enzymes in rat gingival tissue homogenates. IHC demonstrated the existence of renin in vessels of the rat gingival tissue. Conclusion: The results presented here clearly show the existence of a local RAS in the rat gingival tissue, which is capable of generating Ang II and other vasoactive peptides in vitro. Further studies are required to identity the role of this local RAS system. Financial support: FAPESP (process #2004/13479-3).