Details

Autor(en) / Beteiligte

• Stohs, S.J.
• Grafström, R.C.
• Burke, M.D.
• Moldéus, P.W.
• Orrenius, S.G.

Titel

The isolation of rat intestinal microsomes with stable cytochrome P-450 and their metabolism of benzo(α)pyrene

Ist Teil von

• Archives of biochemistry and biophysics, 1976-11, Vol.177 (1), p.105-116

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

1976

Quelle

Elsevier Journal Backfiles on ScienceDirect (DFG Nationallizenzen)

Beschreibungen/Notizen

• A procedure has been developed for the isolation of microsomes from rat intestinal mucosa with stable cytochrome P-450. Preservation of the hemoprotein has been obtained by including trypsin inhibitor, glycerol, and heparin in the homogenization medium. The spectral properties of the hemoprotein from control and phenobarbital (Pb)- and 3-methylcholanthrene (MC)-treated rats were examined. In fed animals, MC given orally resulted in a 30-fold stimulation of benzo(α)pyrene (BP) monooxygenase within 24 h with a simultaneous increase in cytochrome P-450 ( P-448) but had no effect on NADPH-cytochrome c reductase activity. The effect of MC on BP monooxygenase and cytochrome P-450 ( P-448) could be seen as early as 1.5 h after oral administration. Pb treatment increased cytochrome P-450 levels but had no effect on NADPH-cytochrome c reductase activity and comparatively little effect on BP monooxygenase. In fasted animals, MC also produced large increases in BP monooxygenase activity when compared to control animals. At 7 μ m α-naphthoflavone, BP monooxygenase was inhibited 96% in microsomes from MC-treated rats and stimulated 4.5-fold in microsomes from control animals. The pattern of BP metabolites was similar for intestinal microsomes from control and MC-treated rats but differed sharply from that produced by hepatic microsomes. The 4,5-oxide of BP constituted one of the major intestinal metabolites with only small amounts of dihydrodiols being formed after a 5-min incubation. It is concluded that the cytochrome P-450-linked monooxygenase system present in the intestinal mucosa differs markedly from the hepatic system with regard to induction properties, substrate specificity, and pattern of BP metabolites.