COMPARISON OF INTERACTIONS OF R(-ISOMER AND S(-)-ISOMER OF BETA-ADRENERGIC PARTIAL AGONISTS, BEFUNOLOL AND CARTEOLOL, WITH HIGH-AFFINITY SITE OF BETA-ADRENOCEPTORS IN THE MICROSOMAL FRACTIONS FROM GUINEA-PIG CILIARY BODY, RIGHT ATRIA AND TRACHEA())

1. The stereoselectivities of beta-adrenergic partial agonists for the high affinity binding site of beta-adrenoceptors in the guinea-pig ci liary body, right atria and trachea were studied. 2. The inhibition cu rves by the S(-)-isomers of befunolol and carteolol were not significa ntly different from that by the R(+)-isomers in the guinea-pig ciliary body. 3. The inhibition curves by the S(-)-isomers of befunolol and c arteolol were about 10 times as potent as the R(+)-isomers in the guin ea-pig atria and trachea. 4. The pK(i) Values of the S(-)-isomers of b efunolol and carteolol were significantly larger than those of R(+)-is omers in the guinea-pig atria and trachea but not larger than those of the R(+)-isomers in the guinea-pig ciliary body. 5. These results sug gest that the high affinity binding site of P-adrenoceptors in ciliary body cannot discriminate stereoselectively between the R(+)- and S(-) -isomers, while in other tissues there is stereoselectivity between th e two enantiomers.