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Plasma beta-endorphin response to exercise in patients with congestive heart failure.

OBJECTIVE
To determine whether the net release of beta-endorphin during exercise, similar to that of norepinephrine, is related to functional disability in patients with congestive heart failure.


BACKGROUND
Plasma beta-endorphin and norepinephrine levels are elevated at rest in patients with heart failure, reflecting a functional disability. The net release of beta-endorphin during exercise in patients with heart failure is unknown.


METHODS
We measured plasma beta-endorphin and norepinephrine levels (respectively: radioimmune and radioenzymatic assay) at rest and during graded exercise testing in 28 patients with congestive heart failure (Weber's class A, 10; B, 9; and C, 9) and in 9 normal subjects.


RESULTS
At rest, plasma beta-endorphin levels were higher in patients in classes B and C than in normal subjects (p < 0.05 and < 0.01, respectively). At peak exercise, patients in different functional classes and normal subjects reached similar beta-endorphin levels. However, the net release of beta-endorphin during exercise was lower in patients in classes B and C than in those in class A and normal subjects (p < 0.01 for both). At rest, plasma norepinephrine levels were significantly higher in patients than in normal subjects (p < 0.01). At peak exercise, norepinephrine levels were significantly lower in class C patients than in normal subjects (p < 0.05), and tended to be lower in patients in classes A and B (p = NS). The net release of norepinephrine during exercise was lower in patients than in normal subjects (p < 0.01). In patients, releases of both beta-endorphin and norepinephrine during exercise were related to peak oxygen consumption and duration of exercise, but not to resting left ventricular ejection fraction.


CONCLUSIONS
In patients with congestive heart failure, the net release of plasma beta-endorphin during exercise is decreased, like norepinephrine, and reflects a functional disability.