Effects of (±)-, (+)- and (—)-Celiprolol on the Rat Left Atria and Portal Vein

Abstract

Abstract Differing effects of (±)-celiprolol at β-adrenoceptors have been reported. The effects of (±)-, (+)- and (—)-celiprolol on the contractile responses of the rat left atria and portal vein have therefore been studied. (±)-Celiprolol did not augment the responses of the atria to electrical stimulation and is therefore not an agonist at β1-adrenoceptors. Prolonged treatment with (±)-celiprolol attenuated the contractile activity of the vein and this effect was blocked by ICI 118,551 and is therefore mediated by agonism at β2-adrenoceptors. The pA2 values for (±)-, (+)- and (–)-celiprolol at the β1-adrenoceptors of the atria were 8·0, 6·0 and 8·6, respectively. On the portal vein, (±)- and (–)-celiprolol produced non-parallel rightward shifts of log isoprenaline attenuation curves with a reduction in isoprenaline maximum responses. This effect of (±)-celiprolol on the vein was not due to slowly reversible antagonism, as the inhibitory effect of (±)-celiprolol was readily reversible.