Plasma epinephrine (EPI) and norepinephrine (NE) levels were examined among healthy men aged 20 to 25 and 60 to 65 years basally and during EPI infusions. On separate days, 14.3 and 42.9 ng/kg/min EPI was administered intravenously for 45 min. Although there was no age difference in venous EPI levels basally, the old had less increase during the EPI infusions. The plasma metabolic clearance rate of EPI was greater among the old men. Plasma NE levels were elevated among the elderly men, but both age groups had an increase in NE during the EPI 42.9 ng/kg/min infusion rate. During EPI infusions, the old men had less increase in systolic but not diastolic blood pressure or heart rate compared with the young men. The different pattern of change in venous EPI levels and increased metabolic clearance rate of EPI observed among the old men could, in part, explain diminisheds end-organ responsivity.
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