Effect of chronic ANG I-converting enzyme inhibition on aging processes. III. Endothelial function of mesenteric arterial bed of rat.

Age-related changes in endothelial (E) function were studied in mesenteric arterial bed (MAB) preparations removed from male, normotensive, WAG/Rij rats. At the age of 6 mo, one-half of the animals was assigned to chronic treatment with a hypotensive dose of an angiotensin I (ANG I)-converting enzyme inhibitor (ACEI; perindopril, 1 mg.kg-1.day-1 po). Animals were killed at 6, 12, 24, or 30 mo of age; the MAB was perfused in vitro, perfusion pressure (PP) being taken as an index of arteriolar tone. Disruption of E function produced a fall in baseline PP in all groups except 30-mo-old rats, suggesting that 1) baseline tone is maintained by the release of E vasoconstrictor factor(s) and 2) this mechanism is impaired in 30-mo-old rats. The muscarinic agonist, carbachol, antagonized vasoconstriction produced by norepinephrine (NE) in the presence of E. This mechanism was impaired in 30-mo-old rats. NE vasoconstriction increased following disruption of E, suggesting that NE release of endothelium-derived relaxing factor attenuates vasoconstriction. This mechanism was impaired in 30-mo-old rats. Chronic ACEI postponed the age-related decrease in E function, possibly due to a direct effect, or an indirect effect via the prolonged hypotensive action of such treatment.