The Vasomotor Impact of Cu/ZnSODs Is Higher in Arterial Smooth Muscle of Early Postnatal Rats Compared to Adult Animals

The mechanisms of vascular tone regulation during early postnatal ontogenesis differ considerably from those in adulthood. We tested the hypothesis that the vasomotor influence of superoxide dismutases is higher in arteries of rats shortly after birth compared to adult animals. Saphenous arteries of 10 to 15 day ("young") and 3 to 4 month ("adult") old rats were studied using quantitative PCR, spectrophotometry, Western blotting, and isometric myography. <i>Sod3</i> mRNA was most abundant in both adult and young saphenous arteries. Total SOD activity, Cu/ZnSODs activity, and SOD3 protein content were higher in young compared to adult arteries. H₂O₂ caused vessel contraction, while elimination of H₂O₂ weakened contractile responses of endothelium-denuded young arteries. The Cu/ZnSOD inhibitor DETC had no influence on contraction of adult arteries, but weakened contraction of endothelium-denuded, but not endothelium-intact arteries of young rats. The latter effect was observed in the presence of the NO-synthase inhibitor L-NNA, but not with the soluble guanylate cyclase inhibitor ODQ. DETC had no effect in the presence of sodium nitroprusside. Thus, Cu/ZnSODs promote contraction of saphenous arteries in the early postnatal period, but not in adult age. This influence of Cu/ZnSODs is counteracted by endothelial NO in early postnatal arteries.