Changes in plasma noradrenaline and adrenaline during isometric exercise.

1. Plasma noradrenaline and adrenaline were measured radioenzymatically in twelve hypertensive and four normotensive subjects before and during handgrip. In the resting arm (n=11), plasma noradrenaline increased by 17% (P<0.01) and plasma adrenaline by 27% (P<0.001). In the exercising arm, plasma adrenaline increased by 97% (P<0.005) but the mean increase of noradrenaline of 10% was not significant (P>0.1). 2. The noradrenaline response suggests a small and variable sympathetic adrenergic response; the significant difference (P<0.05) in adrenaline responses between resting and exercising arms may reflect local variation in tissue clearance.