Characterization of hepatic and pulmonary cytochromes P-450 in 3-methylcholanthrene-treated hamsters.
Two major forms of hepatic cytochrome P-450 (hepatic P-450MCI and P-450MCII) were purified approximately 5-fold from liver microsomes in Syrian golden hamsters treated with 3-methylcholanthrene (MC). The purified preparations of hepatic P-450MCI and P-450MCII contained 9.6 and 8.3 nmol cytochrome P-450 (P-450) per mg protein, respectively, and were essentially free from NADPH-cytochrome c (P-450) reductase (fpT), NADH-cytochrome b5 reductase and cytochrome b5. By sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the molecular weights of hepatic P-450MCI and P-450MCII were estimated to be 56,000 and 53,500. Further, a major form of pulmonary P-450 (P-450MC) were purified from lung microsomes of MC-treated hamster, and contained 14.2 nmol P-450 per mg protein, and estimated to be 56,000 in monomeric molecular weight, indicating the similar molecular weight to hepatic P-450MCI in the hamster. From the absorption spectra the oxidized forms of hepatic P-450MCI and P-450MCII were high- and low-spin ferric hemoproteins, respectively, and pulmonary P-450MC was similar to hepatic P-450MCII in their hemoprotein spin state. No difference, however, was observed in the CO-reduced forms among hepatic P-450MCI, P-450MCII and pulmonary P-450MC, all exhibiting 446.5 nm Soret bands. In a reconstituted system containing fpT and dilauroylphosphatidylcholine (DLPC), pulmonary P-450MC efficiently catalyzed benzo[a]pyrene (BP) hydroxylation at a rate of 11.4 mol formed per min per mol P-450, but hepatic P-450MCI and P-450MCII both exhibited lower levels, e.g., 0.49 and 0.54, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D001711:Biotransformation; D002384:Catalysis; D006224:Cricetinae; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000302:isolation & purification*; D004790:Enzyme Induction; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008168:Lung / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D008647:Mesocricetus; D008748:Methylcholanthrene / Q000494:pharmacology*; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism
D008748:Methylcholanthrene; D003577:Cytochrome P-450 Enzyme System; D009251:NADPH-Ferrihemoprotein Reductase