Cardiovascular responses and plasma catecholamines in old age.

Plasma catecholamines and haemodynamic responses to isometric handgrip, orthostatic body position and dynamic cycle exercise were studied in 10 healthy old men (mean age 71 years) and 10 healthy young men (mean age 26 years). At rest, plasma noradrenaline (NA) was significantly higher in the old age group. During handgrip there were greater increases in heart rate and blood-pressure in the young rather than in the old men, while forearm blood-flow increase was similar in the two age groups, and there was no increase in NA in either groups. In the orthostatic position heart rate increased in the young men only, and forearm blood-flow decreased more in the young than in the old men. NA concentration increased similarly in both age groups. During dynamic exercise the increases in both the heart rate and the blood-pressure, at similar relative submaximal as well as maximal loads, were smaller in the old men. At maximal work NA and adrenaline (A) concentrations were higher in the young men, while at the lowest load, NA concentration was higher in the old men. Similar increases in exercise heart rate, blood-pressure or rate of perceived exertion corresponded to lower increases in NA in the old men. It can be concluded that old men, compared with young men, have a reduced maximal capacity to release NA and A upon provocation. In addition, the sensitivity for catecholamines in the target organ is reduced with age, as suggested by the smaller increases in heart rate and blood-pressure for a given increase in NA during exercise. The higher basal NA level and the higher NA level, during moderate provocation, may suggest a compensatory increase in activity.