beta-Adrenoceptors potentiate alpha1-adrenoceptor-mediated inotropic response in rat left atria.
OBJECTIVE
To investigate whether stimulation of beta-adrenoceptor (AR) and its subtypes augment alpha1-AR-evoked positive inotropic response and inositol phosphate (InsP) accumulation in isolated rat left atria.


METHODS
Inotropic response was determined by contractile function experiment in isolated electrically driven rat left atria. 3H-InsP accumulations were measured by 3H-inositol incorporation and column chromatography.


RESULTS
(1) Stimulation of alpha1-AR by phenylephrine (PE) or norepinephrine (NE) in the presence of propranolol (Prop) evoked positive inotropic response and 3H-InsP accumulations, while stimulation of beta-AR by isoprenaline (ISO) or NE in the presence of phentolamine (Phen) only evoked positive inotropic response, but not 3H-InsP accumulations. (2) Simultaneous stimulation of alpha1- and beta-AR by NE or ISO plus PE significantly shifted the concentration-dependent inotropic response curves and 3H-InsP accumulation curves to the left and upward compared with individual alpha1-AR stimulation by PE or NE in the presence of Prop. (3) In the presence of ICI118551 (selective beta2-AR antagonist) or CGP12177 (selective beta1-AR antagonist), stimulation of either beta1- or beta2-AR did not change alpha1-AR-evoked inotropic response and 3H-InsP accumulations.


CONCLUSIONS
Stimulation of beta1-AR and beta2-AR potentiates alpha1-AR-mediated positive inotropic response and InsP accumulation in isolated rat left atria.
Zhang
Yong-Zhen
YZ
Institute of Vascular Medicine, Peking University Third Hospital; Key Laboratory of Ministry of Education for Molecular Cardiovasology, Beijing 100083, China.
Zhang
You-Yi
YY
Chen
Ming-Zhe
MZ
Han
Qi-De
QD
D058646:Adrenergic alpha-1 Receptor Agonists; D058668:Adrenergic alpha-1 Receptor Antagonists; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D016279:Atrial Function, Left; D006352:Heart Ventricles / Q000378:metabolism; D066298:In Vitro Techniques; D007295:Inositol Phosphates / Q000378:metabolism*; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D013268:Stimulation, Chemical
D058646:Adrenergic alpha-1 Receptor Agonists; D058668:Adrenergic alpha-1 Receptor Antagonists; D000319:Adrenergic beta-Antagonists; D007295:Inositol Phosphates; D018340:Receptors, Adrenergic, alpha-1; D011943:Receptors, Adrenergic, beta; D010656:Phenylephrine; D009638:Norepinephrine