—We analyzed the influence of aging and genetic hypertension on the function and expression of soluble guanylyl cyclase (sGC) in the aortas of prehypertensive and old spontaneously hypertensive rats (SHR) as well as in age-matched normotensive Wistar-Kyoto rats (WKY). The expression of heterodimeric sGC (α₁ and β₁) was assessed at the mRNA and protein level, and its function was assessed by the relaxant responses of phenylephrine-contracted endothelium-denuded aortic rings to the nitric oxide (NO) donor sodium nitroprusside. The vasodilator potency of sodium nitroprusside was significantly reduced (P<0.05) with age (3- to 6-fold increase in the EC₅₀ in old WKY and SHR compared with their young counterparts) as well as with hypertension (3-fold increase in old SHR compared with age-matched WKY), whereas the vasodilator potency of sodium nitroprusside did not differ between young SHR and WKY. A similar influence of aging and hypertension on NO-stimulated GC activity was revealed at the GC expression level: Whereas the β₁ protein content was similar in young rats of both strains, old WKY exhibited 60% lower and old SHR exhibited 80% lower β₁ subunit protein compared with young rats (P<0.05). Moreover, the abundance of α₁ and β₁ mRNA (assessed by reverse transcriptase—polymerase chain reaction) was similar in young rats but was 2.5-fold (α₁) and 4.3-fold (β₁) lower in old SHR compared with old WKY. In conclusion, our findings show that both aging and hypertension decrease sGC expression and its NO-dependent activation in aortic tissue. Downregulation of sGC may therefore contribute to arterial dysfunction in senescence and chronic hypertension.