Sympathetic alterations after sodium restriction and short-term captopril administration.

OBJECTIVES

The purpose of this study was to examine the effects of short-term captopril therapy during sodium restriction on several markers of the sympathetic nervous system, including plasma norepinephrine, neuropeptide Y, beta-adrenergic receptors and cortisol.

BACKGROUND

Recent studies suggest that the therapeutic effects of converting enzyme inhibitors involve not only the renin-angiotensin and prostaglandin systems but also the sympathetic system.

METHODS

Twelve hypertensive and 20 normotensive men were studied after 2 5-day hospital stays during which they consumed a 10-mEq sodium diet and received captopril (25 mg twice daily) or placebo in a double-blind crossover study.

RESULTS

Captopril decreased neuropeptide Y (p < 0.05) and angiotensin II (p < 0.01) and increased isoproterenol-stimulated cyclic adenosine monophosphate (AMP) in lymphocytes (p < 0.03), plasma norepinephrine (p < 0.02), cortisol (p < 0.05) and renin (p < 0.001) in both hypertensive and normotensive subjects. Hypertensive subjects had an increased beta-adrenergic receptor density (p < 0.02) and a greater decrease in diastolic blood pressure compared with normotensive subjects (p < 0.02).

CONCLUSIONS

The results of this study suggest that the short-term therapeutic effects of captopril may involve concerted changes in key components of the sympathetic nervous system. These findings, such as decreased neuropeptide Y combined with increased norepinephrine and beta-adrenergic receptors, are compatible with the observation of increased cardiac output and decreased peripheral resistance after short-term angiotensin-converting enzyme inhibition.