Adrenaline and noradrenaline increase contractile force of human ventricle through both beta 1- and beta 2-adrenoceptors.
Several paradoxical findings have come to light with regard to the function of beta 1- and beta 2-adrenoceptors that coexist in human ventricular myocardium. Although a predominance of beta 1 (greater than 2/3) was found in membrane particles, stimulation of the adenylate cyclase was mostly through beta 2 (5/6 adrenaline and 2/3 noradrenaline). One beta 2-adrenoceptor generates 4-12 times more cAMP.s-1 than one beta 1-adrenoceptor. Both adrenaline and noradrenaline can enhance maximally contractile strength through beta 1. Low adrenaline concentrations and high noradrenaline concentrations can increase contractile strength by up to 50% of maximum through beta 2. The question as to whether beta 1- or beta 2 augment contractile strength at a different oxygen cost still needs elucidation.
Kaumann
A J
AJ
Department of Clinical Physiology, University of Dusseldorf, FRG.
D000242:Cyclic AMP / Q000378:metabolism; D004837:Epinephrine / Q000494:pharmacology*; D006352:Heart Ventricles / Q000187:drug effects; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects* / Q000502:physiology; D016276:Ventricular Function
D007093:Imidazoles; D011943:Receptors, Adrenergic, beta; C049763:CGP 20712A; D000242:Cyclic AMP; D009638:Norepinephrine; D004837:Epinephrine