TY - JOUR
T1 - Identification of P-450ALC in microsomes from alcohol dehydrogenase-deficient deermice
T2 - Contribution to ethanol elimination in vivo
AU - Handler, Jeffrey A.
AU - Koop, Dennis R.
AU - Coon, Minor J.
AU - Takei, Yoshiyuki
AU - Thurman, Ronald G.
PY - 1988/7
Y1 - 1988/7
N2 - Isozyme 3a of rabbit hepatic cytochrome P-450, also termed P-450ALC, was previously isolated and characterized and was shown to be induced 3- to 5-fold by exposure to ethanol. In the present study, antibody against rabbit P-450ALC was used to identify a homologous protein in alcohol dehydrogenase-negative (ADH-) and -positive (ADH+) deermice, Peromyscus maniculatus. The antibody reacts with a single protein having an apparent molecular weight of 52,000 on immunoblots of hepatic microsomes from untreated and ethanol-treated deermice from both strains. The level of the homologous protein was about 2-fold greater in microsomes from naive ADH- than from naive ADH+ animals. Ethanol treatment induced the protein about 3-fold in the ADH+ strain and about 4-fold in the ADH- strain. The antibody to rabbit P-450ALC inhibited the microsomal metabolism of ethanol and aniline. The homologous protein, termed deermouse P-450ALC, catalyzed from 70 to 80% of the oxidation of ethanol and about 90% of the hydroxylation of aniline by microsomes from both strains after ethanol treatment. The antibody-inhibited portion of the microsomal activities, which are attributable to the P-450ALC homolog, increased about 3-fold upon ethanol treatment in the ADH+ strain and about 4-fold in the ADH- strain, in excellent agreement with the results from immunoblots. The total microsomal P-450 content and the rate of ethanol oxidation were induced 1.4-fold and 2.2-fold, respectively, by ethanol in the ADH+ strain and 1.9-fold and 3.3-fold, respectively, in the ADH- strain. Thus, the total microsomal P-450 content and ethanol oxidation underestimate the induction of the P-450ALC homolog in both strains. A comparison of the rates of microsomal ethanol oxidation in vitro with rates of ethanol elimination in vivo indicates that deermouse P-450ALC could account optimally for 3 and 8% of total ethanol elimination in naive ADH+ and ADH- strains, respectively. After chronic ethanol treatment, P-450ALC could account maximally for 8% of the total ethanol elimination in the ADH+ strain and 22% in the ADH- strain. Further, cytochrome P-450ALC appears to be responsible for about one-half of the increase in the rate of ethanol elimination in vivo after chronic treatment with ethanol. These results indicate that the contribution of P-450ALC to ethanol oxidation in the deermouse is relatively small. Desferrioxamine had no effect on rates of ethanol uptake by perfused livers from ADH-negative deermice, indicating that ethanol oxidation by a hydroxyl radical-mediated mechanism was not involved in ethanol metabolism in this mutant. Peroxisomal β-oxidation capacity was increased 40% over control values by ethanol treatment, consistent with the hypothesis that the increase in ethanol elimination in the ADH-negative deermouse is mediated predominantly via catalase-H2O2.
AB - Isozyme 3a of rabbit hepatic cytochrome P-450, also termed P-450ALC, was previously isolated and characterized and was shown to be induced 3- to 5-fold by exposure to ethanol. In the present study, antibody against rabbit P-450ALC was used to identify a homologous protein in alcohol dehydrogenase-negative (ADH-) and -positive (ADH+) deermice, Peromyscus maniculatus. The antibody reacts with a single protein having an apparent molecular weight of 52,000 on immunoblots of hepatic microsomes from untreated and ethanol-treated deermice from both strains. The level of the homologous protein was about 2-fold greater in microsomes from naive ADH- than from naive ADH+ animals. Ethanol treatment induced the protein about 3-fold in the ADH+ strain and about 4-fold in the ADH- strain. The antibody to rabbit P-450ALC inhibited the microsomal metabolism of ethanol and aniline. The homologous protein, termed deermouse P-450ALC, catalyzed from 70 to 80% of the oxidation of ethanol and about 90% of the hydroxylation of aniline by microsomes from both strains after ethanol treatment. The antibody-inhibited portion of the microsomal activities, which are attributable to the P-450ALC homolog, increased about 3-fold upon ethanol treatment in the ADH+ strain and about 4-fold in the ADH- strain, in excellent agreement with the results from immunoblots. The total microsomal P-450 content and the rate of ethanol oxidation were induced 1.4-fold and 2.2-fold, respectively, by ethanol in the ADH+ strain and 1.9-fold and 3.3-fold, respectively, in the ADH- strain. Thus, the total microsomal P-450 content and ethanol oxidation underestimate the induction of the P-450ALC homolog in both strains. A comparison of the rates of microsomal ethanol oxidation in vitro with rates of ethanol elimination in vivo indicates that deermouse P-450ALC could account optimally for 3 and 8% of total ethanol elimination in naive ADH+ and ADH- strains, respectively. After chronic ethanol treatment, P-450ALC could account maximally for 8% of the total ethanol elimination in the ADH+ strain and 22% in the ADH- strain. Further, cytochrome P-450ALC appears to be responsible for about one-half of the increase in the rate of ethanol elimination in vivo after chronic treatment with ethanol. These results indicate that the contribution of P-450ALC to ethanol oxidation in the deermouse is relatively small. Desferrioxamine had no effect on rates of ethanol uptake by perfused livers from ADH-negative deermice, indicating that ethanol oxidation by a hydroxyl radical-mediated mechanism was not involved in ethanol metabolism in this mutant. Peroxisomal β-oxidation capacity was increased 40% over control values by ethanol treatment, consistent with the hypothesis that the increase in ethanol elimination in the ADH-negative deermouse is mediated predominantly via catalase-H2O2.
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U2 - 10.1016/0003-9861(88)90576-0
DO - 10.1016/0003-9861(88)90576-0
M3 - Article
C2 - 3395117
AN - SCOPUS:0023820754
SN - 0003-9861
VL - 264
SP - 114
EP - 124
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
IS - 1
ER -