Hydroxylase, benzo pyrene hepatic microsomal

Bend, J. R., Hall, P., and Foureman, G. L. Comparison of benzo(a)pyrene hydroxylase (aryl hydrocarbon hydroxylase, AHH) activities in hepatic microsomes from untreated and 1,2,3,4-dibenzanthracene (DBA)-induced little skate (Raja erinacea). Bull. Mt. Desert Island Biol. Lab. (1976) 16. 3-5. 

Rats were dosed with soil suspensions, by gavage, either once or for four consecutive days. Total TCDD dosages administered to rats were either 10 ug TCDD/kg or 40 ug/ TCDD/kg. Rats were sacrificed 24 hours after the final dose, autopsied, and hepatic microsomal fractions were collected. Aryl hydrocarbon hydroxylase (AHH) levels were determined in the microsomes, using the fluorescent assay of the product of the metabolism of benzo(a)pyrene to 3-OH benzo(a)pyrene (16). 

Figure 9.1. Sex-differences in rat hepatic microsomal drug metabolism. Data shown are based on enzyme assays in rat liver microsomes using the three indicated xenobiotic substrates ethylmorphine (EM), benzo[o] pyrene (BP), and hexobarbital (HB). Ethylmorphine A -demethylase and benzo[a]pyrene hydroxylase activities are expressed as nmol product formed per minute per mg microsomal protein, whereas hexobarbital hydroxylase activity is expressed as nmol product formed per 30 min per g liver. Also shown is hepatic microsomal total cytochrome P450 content, which is expressed as nmol per mg microsomal protein (values multiplied by 10). The data are shown as mean SD for 4 or 5 rats, except for ethylmorphine W-demethylase and total P450 which are based on a pool of 6 livers.

Benzo(a)pyrene hydroxylase activities in hepatic and intestinal microsomes of fiber-fed rats are presented in Table VIII. There were no significant differences (0.05 level) among any of the purified fiber treatment groups in either liver or intestinal microsomes. Lab Chow-fed rats had the lowest liver microsomal benzo(a)pyrene hydroxylase (AHH) level. The indication of enhanced intestinal P-448-dependent hydroxylation of biphenyl in the pectin-fed rats (seen as elevated 3-hydroxybiphenyl formation in microsomes, Table Vl) was not supported by these preliminary data. 

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