INFLUENCES OF AGE AND SEX ON ENDOTHELIUM-DEPENDENT VASCULAR-RESPONSESAND ARTERIAL BLOOD-PRESSURE IN THE RAT

1. Vascular reactivity related to age and sex on two endothelium-depen dent effects in isolated rat aorta (acetylcholine-induced relaxation a nd modulation of noradrenaline response) and blood pressure decreases by acetylcholine administration were studied. Group of male Wistar rat s aged 2, 4, 8, 16 and 24 months plus female rats of 4 months were use d. 2. Blood pressure was measured by using a standard tail-cuff techni que. Acetylcholine in vivo administration (0.002 mg/kg i.v.) significa ntly reduced diastolic pressures in the 2 month old males and 4 month old females, but not in other age groups. 3. Isolated helical strips o f rat aorta were used to determine the endothelium-dependent reactivit y. The maximal relaxation from different groups of male rats induced b y acetylcholine was: 100% in those of 2 months; 53.2 +/- 6.0% in those of 4 months; 61.8 +/- 6.1% in those of 8 months; 57.6 +/- 5.0% in tho se of 16 months and 31.0 +/- 4.9% in those of 24 months. Concentration -response curves to noradrenaline were significantly greater only when endothelial eels were removed from aorta strips of 2 month old rats. In aorta strips with endothelium the maximal contraction to noradrenal ine was significantly greater in 2 month aid rats when compared with t he other groups and smaller in aorta strips from 24 month old rats. 4. These results suggest that the endothelium-dependent effects studied and the noradrenaline-induced contraction decreased according to the a ge of the rats.