Abstract 665: Endothelial Nitric Oxide Negatively Modulates Phenylephrine-induced Contraction In Matrix Metalloproteinase 2 (mmp-2)-filled Rabbit Aortic Rings

Abstract

Endothelial nitric oxide negatively modulates Phenylephrine-induced contraction in Matrix metalloproteinase 2 (MMP-2)-filled rabbit aortic rings The present study aimed to evaluate the vascular function of aortic rings after intraluminal injection of matrix metalloproteinase 2 (MMP-2) and contribution of endothelial nitric oxide (NO) in this response. METHODS: thoracic aorta isolated from New Zealand rabbits (3.0 Kg) was isolated and were performed in situ gelatinolytic assay (intraluminal exposure with Krebs solution or MMP-2 1.2 μg/mL, at 37° C for 30 minutes, with measure of fluorescence intensity - FI) or vascular reactivity. Cumulative concentration-effect curves for phenylephrine (PE, 0.1 nM - 10 μM/L) were performed in endothelium-intact (E+) or denuded (E-) aortic rings, in the absence or presence of L-NAME (non-selective inhibitor of NOS, 100 μM) or Hydroxycobalamine (scavenger of intracellular NO), 30 min before the PE curves on E+ rings. The vascular contraction was normalized by grams of tension by dry tissue (g/g) and were analyzed the agonist maximum effect (Emax) and potency (pD2). Data represent mean ± S.E.M and the results were statistically analyzed using Student t test, one-way or two-way ANOVA with Bonferroni pos-hoc (p<0,05). Results: In situ gelatinolytic activity was increased in the vessels filled with MMP-2 (19.19+0.93U,n=5) compared to vehicle (10.75+0.45U,n=5). In the vascular reactivity, E- aortic rings filled with MMP-2 increased Emax of PE (1893,28+122,40g/g,n=9) versus vehicle E- (1485.73+76.82g/g,n=9), but no differences were observed on Emax of E+ aortic rings (vehicle: 1416.13+120.87g/g,n=7; MMP-2: 1893.28+122.40g/g,n=9). The presence of L-NAME induced an increase in Emax of E+ aortic rings filled with vehicle (1817.60+76.37g/g,n=7) or MMP-2 (2340.50+130.43g/g,n=5). Hydroxycobalamine also increased the Emax of E+ aortic rings with vehicle (1889,81+129,17,n=6) or MMP-2 (2480,12+192,57,n=5). No difference of pD2 value was observed in this study. Conclusion: Data suggest this protease cross the aorta layers from the lumen. An increased vasoconstriction in E- vessels suggests a vascular smooth muscle activity of MMP-2. In the presence of L-NAME and Hydroxycobalamine, vessels filled with MMP-2 shows a greater maximum effect suggesting that NO exerts a negative modulation of the PE-induced vasoconstriction on MMP-2 aortic rings.