TY - JOUR
T1 - Cytochrome P450 enzymes involved in the enhancement of propranolol N-desisopropylation after repeated administration of propranolol in rats
AU - Narimatsu, Shizuo
AU - Mochida, Masayuki
AU - Matsumoto, Takahiro
AU - Masubuchi, Yasuhiro
AU - Horie, Toshiharu
AU - Nagata, Kiyoshi
AU - Funae, Yoshihiko
AU - Cho, Arthur K.
AU - Suzuki, Tokuji
N1 - Funding Information:
We are very grateful to Drs. M. Kitada and S. Ohmori, Chiba University Hospital, for their kind gift of purified cytochromeb ,. This work was supportedi n part by a grant from Japan ResearchF oundation for Clinical Pharmacologyt o S.N.
PY - 1996/9/6
Y1 - 1996/9/6
N2 - Repeated oral administration of propranolol (PL, 100 mg/kg daily, for 5, 10 and 15 days) to male Wistar rats increased PL N-desisopropylase and decreased PL 4-,5- and 7-hydroxylase activities in liver microsomes. The increase was highest at the 10 day time point whereas the decrease was relatively constant over the 15 day treatment period. There were no significant changes in the total content of cytochromes P450 (450) or cytochrome b5, or in NADPH-cytochrome c reductase activity during the PL treatment. The enhanced N-desisopropylase activities were markedly inhibited by α-naphthoflavone (a P450-1A1/2 inhibitor), and moderately by triacetyloleandomycin (a P450-3A1/2 inhibitor) and diethyldithiocarbamate (a P450-2E1 inhibitor). Phenacetin O-deethylase activity, an index of P450-1A2, was significantly increased on day 5, 10 and 15 of the treatment, whereas p-nitrophenol hydroxylase activity was elevated on day 10 only. The PL N-desisopropylation showed a strong and significant correlation with phenacetin O-deethylation, and a weaker but significant correlation with p-nitrophenol hydroxylation. Immunoblot analysis revealed that a protein band corresponding to P450-1A2 was increased by PL pretreatment, and protein band corresponding to P450-3A tended to be increased slightly, but other protein band corresponding to the subfamily of P450-2B, -2C, or -2E was not changed. Pretreatment of rats with P450 inducers (β-naphthoflavone, phenobarbital, acetone and dexamethasone) increased PL N-dealkylase activity in liver microsomes. Furthermore, antibodies raised against P450-1A and -3A enzymes, suppressed PL N-desisopropylation in a concentration-dependent manner, but P450-2E antibody did not. Reconstitution studies showed that P450-1A1, -1A2, -2E1 and -3A2 exhibited catalytic activities for PL N-dealkylation. These results suggest that P450-1A2 is a major PL N-desisopropylase in the PL-treated rats, and P450-3A related enzyme(s) and P450-2E1 as a moderate or minor enzyme are also involved in PL N-dealkylation in native and PL-treated rats.
AB - Repeated oral administration of propranolol (PL, 100 mg/kg daily, for 5, 10 and 15 days) to male Wistar rats increased PL N-desisopropylase and decreased PL 4-,5- and 7-hydroxylase activities in liver microsomes. The increase was highest at the 10 day time point whereas the decrease was relatively constant over the 15 day treatment period. There were no significant changes in the total content of cytochromes P450 (450) or cytochrome b5, or in NADPH-cytochrome c reductase activity during the PL treatment. The enhanced N-desisopropylase activities were markedly inhibited by α-naphthoflavone (a P450-1A1/2 inhibitor), and moderately by triacetyloleandomycin (a P450-3A1/2 inhibitor) and diethyldithiocarbamate (a P450-2E1 inhibitor). Phenacetin O-deethylase activity, an index of P450-1A2, was significantly increased on day 5, 10 and 15 of the treatment, whereas p-nitrophenol hydroxylase activity was elevated on day 10 only. The PL N-desisopropylation showed a strong and significant correlation with phenacetin O-deethylation, and a weaker but significant correlation with p-nitrophenol hydroxylation. Immunoblot analysis revealed that a protein band corresponding to P450-1A2 was increased by PL pretreatment, and protein band corresponding to P450-3A tended to be increased slightly, but other protein band corresponding to the subfamily of P450-2B, -2C, or -2E was not changed. Pretreatment of rats with P450 inducers (β-naphthoflavone, phenobarbital, acetone and dexamethasone) increased PL N-dealkylase activity in liver microsomes. Furthermore, antibodies raised against P450-1A and -3A enzymes, suppressed PL N-desisopropylation in a concentration-dependent manner, but P450-2E antibody did not. Reconstitution studies showed that P450-1A1, -1A2, -2E1 and -3A2 exhibited catalytic activities for PL N-dealkylation. These results suggest that P450-1A2 is a major PL N-desisopropylase in the PL-treated rats, and P450-3A related enzyme(s) and P450-2E1 as a moderate or minor enzyme are also involved in PL N-dealkylation in native and PL-treated rats.
KW - 4-Hydroxylation
KW - Cytochrome P450-1A2
KW - Enzyme induction
KW - Enzyme inhibition
KW - N-Desisopropylation
KW - Propranolol
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U2 - 10.1016/0009-2797(96)03726-X
DO - 10.1016/0009-2797(96)03726-X
M3 - Article
C2 - 8870689
AN - SCOPUS:0030572727
SN - 0009-2797
VL - 101
SP - 207
EP - 224
JO - Chemico-Biological Interactions
JF - Chemico-Biological Interactions
IS - 3
ER -