摘要:
1. The metabolism of carteolol, a beta-adrenoceptor blocking drug, was investigated in male Sprague-Dawley rat liver microsomes.2. The formation of 8-hydroxycarteolol was the principal metabolic pathway of carteolol in vitro and followed Michaelis-Menten kinetics with a K-m = 11.0+/-5.4 mu M and a V-max = 1.58 +/- 0.64 nmol/min/nmol P450 respectively (mean +/-SD, n = 5). Eadie-Hofstee plot analysis of carteolol 8-hydroxylase activity confirmed single-enzyme Michaelis-Menten kinetics.3. The cytochrome P450 isoforms involved in B-hydroxylation of carteolol were investigated using selective chemical inhibitors and polyclonal anti-P450 antibodies. Quinine (K-i = 0.06 mu M) and quinidine (K-i = 2.0 mu M), selective inhibitors of CYP2D1, competitively inhibited 8-hydroxycarteolol formation. Furthermore, only anti-human CYP2D6 antibody inhibited this reaction.4. These results suggest that carteolol is metabolized to 8-hydroxycarteolol by CYP2D1. The K-m of carteolol for CYP2D1 in male rat liver microsomes was much greater than those of propranolol or bunitrolol, indicating that carteolol has a lower affinity for CYP2D1 compared with these other beta-adrenoceptor blocking drugs.