Abstract
Heart rate, blood pressure, forearm vascular resistance (FVR), and catecholamine and renin responses to head-up tilt at 80 degrees and cold pressor test were investigated in 15 hypertensive men aged less than fifty-five (mean 44 ± 7 years; M ± SD) and 13 similarly hypertensive men aged more than fifty-five (mean 62 ± 4 years; M±SD). Baseline plasma norepinephrine levels, as well as norepinephrine responses to tilt and cold pressor stress, were similar in the two groups, suggesting a lack of age-related increase in plasma norepi nephrine (NE) responses in patients with essential hypertyension. Normalized FVR responses (% change) to tilting (28 ± 21 vs 95 ± 36; M ± SE) and cold pressor test (33 ± 12 vs 64±21; M ± SE) were signifiantly less (p<0.01) in older hypertensives. These results, but not the plasma NE responses to reflex sym pathetic activation by tilt and cold pressor testing in older hypertensives, sug gest an impaired forearm vasoconstriction.
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