Angiotensin converting enzyme inhibition and sympathetic activity in healthy subjects.
BACKGROUND
One suggested mechanism for the reduction in mortality rates resulting from the use of angiotensin converting enzyme inhibitors in congestive heart failure is the inhibition of the angiotensin II-mediated norepinephrine release. Direct evidence for this mechanism is lacking in humans.


METHODS
We examined the effects of captopril, 25 mg three times a day, or matched placebo for 7 days on sympathetic activity during a 10 mEq/day sodium diet in seven healthy male subjects aged 30 +/- 3 (SEM) years. A tritiated norepinephrine radioisotope dilution technique was used to measure sympathetic activity, both at rest and during isometric handgrip exercise.


RESULTS
Captopril blunted the increase in mean arterial pressure during isometric handgrip exercise (placebo, from 81 +/- 4 to 112 +/- 2 mm Hg; captopril, from 78 +/- 3 to 101 +/- 2 mm Hg; p < 0.01). However, the increase in systemic norepinephrine spillover during isometric handgrip exercise was not blunted by captopril. Captopril had no effect on resting mean arterial pressure or systemic norepinephrine spillover.


CONCLUSIONS
Captopril did not attenuate baseline or static exercise-stimulated sympathetic activity in healthy subjects. These findings would indicate that angiotensin converting enzyme inhibition does not decrease sympathetic activity at rest or during the stimulus of isometric handgrip exercise.
Lang
C C
CC
Division of Clinical Pharmacology, Vanderbilt University, Nashville, TN 37232-6602, USA.
Stein
C M
CM
He
H B
HB
Wood
A J
AJ
D000328:Adult; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D002216:Captopril / Q000494:pharmacology*; D004311:Double-Blind Method; D015444:Exercise; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D009638:Norepinephrine / Q000097:blood* / Q000493:pharmacokinetics; D011865:Radioisotope Dilution Technique; D012083:Renin / Q000097:blood; D012146:Rest; D013564:Sympathetic Nervous System / Q000187:drug effects*
D000806:Angiotensin-Converting Enzyme Inhibitors; D002216:Captopril; D012083:Renin; D009638:Norepinephrine