Effects of (+/-)-, (+)- and (-)-celiprolol on the rat left atria and portal vein.

Differing effects of (+/-)-celiprolol at beta-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 beta 1-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 beta 2-adrenoceptors. The pA2 values for (+/-)-, (+)- and (-)-celiprolol at the beta 1-adrenoceptors of the atria were 8.0, 6.0 and 8.6, respectively. On the protal 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.