Repeated Immobilization Stress Increases Expression of β3-Adrenoceptor in the Left Ventricle and Atrium of the Rat Heart

Stress is a contributor of many cardiovascular diseases. Positive inotropic and chronotropic effects of catecholamines are regulated via beta-adrenergic receptors (ARs). Many reports exist concerning changes of cardiac beta(1)- and beta(2)-ARs in stress, but only a few deal with modulation of cardiac beta(3)-AR. Our aim was to analyze the expression and binding sites of beta(1)-, beta(2)- and beta(3)-ARs and adenylyl cyclase activity in the left ventricle, and beta(3)-AR expression and binding in the left atrium of rats exposed to acute and chronic immobilization stress (IMO). The concentration of noradrenaline in the ventricle decreased, while adrenaline increased, especially after repeated IMO. The mRNA and protein levels, and binding sites of beta(3)-subtype significantly rose following chronic IMO, while all parameters for beta(2)-AR dropped after single and repeated exposure. Similarly, the mRNA levels and binding sites for beta(3)-subtype increased in the left atrium as a consequence of chronic IMO. The rise in beta(3)-subtypes and a drop in beta(2)-subtypes resulted in inhibition of adenylyl cyclase activity within the left ventricle. Taken together, among other factors, up-regulation of beta(3)-AR could represent an adaptation mechanism, which might be related to altered physiological function of the left ventricle and atrium during prolonged emotional stress and might serve cardioprotective function during catecholamine overload. Copyright (C) 2013 John Wiley & Sons, Ltd.