MMP2 and endothelial dysfunction: However, RUPP-induced endothelial dysfunction is followed by decreases in both vascular MMP-2 activity and circulating NO levels with concomitant increases in vascular contraction, but when circulating NO levels were restored by sodium nitrite treatment under the RUPP condition, there was a recovery of the gelatinolytic activity of vascular MMP-2, thus normalizing vascular contraction in aortas from RUPP + Nitrite rats (Figure 5 and Supplementary Table S1).