Cigarette Smoking Alters Sympathoadrenal Regulation by Decreasing the Density of β2-Adrenoceptors. A Study of Monitored Smoking Cessation

Abstract

We report the effects of monitored smoking cessation on adrenergic regulation in chronic smokers. The beta 2 adrenoceptor density of mononuclear leukocytes (MNLs) and plasma catecholamines was analyzed before cessation and 2, 3, and 8 weeks after cessation. We found a progressive increase in beta-adrenoceptor density after smoking cessation. During smoking the beta-adrenoceptor density was 1.456 +/- 83 (mean +/- SEM) binding sites per cell (n = 10), whereas 3 weeks after cessation the density was 1,774 +/- 157 sites per cell (n = 10; p less than 0.05), and at 8 weeks, 1,900 +/- 227 sites per cell (n = 8; p less than 0.05), representing an overall increase of 23%. Smoking cessation had no effect on binding affinity nor on lymphocyte subgroup distribution. The density of MNL cell beta-adrenoceptors in age-matched nonsmoking men was higher, at 1,896 +/- 271 sites per cell, than that of the chronic smokers before cessation, 1,419 +/- 117 sites per cell (n = 14; p less than 0.01). Plasma epinephrine decreased as a result of cessation from 0.36 pmol/ml (0.26-0.44, 95% confidence interval; baseline) to 0.26 pmol/ml (0.20-0.32) at 8 weeks (p less than 0.05), and norepinephrine decreased from 2.09 pmol/ml (1.38-2.80) to 1.69 pmol/ml (1.14-2.24; p = 0.06). We conclude that stopping smoking progressively increases beta 2-adrenoceptor density on MNL cells. Eight weeks after cessation the adrenoceptor density reaches the corresponding level of nonsmokers. These reversible changes in adrenergic regulation after smoking cessation may be associated with the relatively rapid reduction in cardiovascular disease risk among ex-smokers.