Placental and hepatic xenobiotic-metabolising activities were studied in smokers and non-smokers, who were classified by anamnestic interview, plasma thiocyanate and plasma cotinine determinations. Plasma thiocyanate assay is inadequate in the classification of smokers and non-smokers. Plasma cotinine levels reflect more accurately the smoking status. The anamnestic smokers remained smokers and several self-declared non-smokers proved to be smokers. On the basis of plasma cotinine determination all real smokers had higher 7-ethoxyresorufin 0-deethylase (ERDE) activities measured either in placental microsomes or liver biopsy homogenates than non-smokers. Classification based on plasma cotinine levels showed a statistically significant (P less than 0.001) difference between smokers and non-smokers in liver homogenate ERDE activity. However, cotinine levels did not correlate with any of the xenobiotic-metabolising activities tested. An objective biochemical marker, such as cotinine determination seems to be necessary when evaluating the effect of smoking on drug metabolism in man.

Aryl Hydrocarbon Hydroxylases↗

PubMedDate not supplied

Immunohistochemical detection of human placental cytochrome P-450-associated mono-oxygenase system inducible by maternal cigarette smoking.

Several xenobiotic-metabolizing mono-oxygenase activities, in conjunction with the immunohistochemical localization of the respective cytochrome P-450 forms, were investigated in placentae from smoking and non-smoking women. The antibodies used in the immunohistochemical analyses were monoclonal antibodies (MAbs) 1-7-1 and 2-66-3, prepared against the 3-methylcholanthrene-induced and phenobarbital-induced rat liver P-450, respectively. The mono-oxygenase activities were higher in placental microsomes from smokers, although no difference was observed in microsomal P-450 content. A distinct positive staining with MAb 1-7-1 was detectable in the trophoblastic layer of all placentae from smokers. In placentae from non-smokers, minimal cytoplasmic staining was observed in large villi in a few trophoblastic cells. The staining reaction was negative when MAb 2-66-3 or non-specific antibody were used. These results demonstrate that maternal cigarette smoking induces in the trophoblastic layer of the placenta a cytochrome P-450 form which is detectable immunohistochemically with the monoclonal antibody to 3-methylcholanthrene-inducible P-450 in rat liver.

Antibodies, Monoclonal↗

PubMedDate not supplied

Effects of phenobarbital and beta-naphthoflavone on cerium induced biochemical changes in rat serum.

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Animals↗

PubMedDate not supplied

Xenobiotic and steroid-metabolizing monooxygenases catalysed by cytochrome P450 and glutathione S-transferase conjugations in the human placenta and their relationships to maternal cigarette smoking.

Placentae from both smoking and non-smoking mothers were studied with respect to P450-dependent xenobiotic and steroid-metabolizing reactions, GSHt activity with different substrates and umbilical blood cotinine levels. Catalytic activities were determined in both freshly prepared homogenate subfractions and subfractions prepared after freezing the tissue sample. The results showed three correlation clusters: (i) AHH and ECDE (P less than 0.001), (ii) ECDE and ERDE (P less than 0.05), and (iii) Arom and CSCC reactions correlated with each other both in the mitochondria and microsomes. Among xenobiotic and steroid metabolizing activities, only CSCC and AHH showed a significant negative correlation. Our results agree with the earlier studies (Gottlieb and Manchester, 1986) reporting that xenobiotic metabolising MO and GSHt reactions did not show any statistically significant correlations, reflecting the fact that maternal cigarette smoking does not affect GSHt activities. However, in placentae from smoking mothers a statistically significant (P less than 0.01) positive correlation between GSHt and Arom activity was found. No plausible biological explanation is available for this finding. Among xenobiotic-metabolizing activities only ERDE correlated with plasma cotinine levels, suggesting that it is most closely related to the extent of maternal cigarette smoking. The present findings also suggest that cigarette smoke induced ERDE activity is a distinct one compared with the other xenobiotic-metabolizing P450s. Negative correlations between xenobiotic-metabolizing MO activities and CSCC lend some support to an earlier suggestion (Juchau et al, 1972) that cigarette smoking affects endogenous steroid-metabolizing CSCC reaction catalyzed by P450. Whether this finding is a true biological phenomenon and what is the mechanism behind it remain to be elucidated.

Cotinine↗

PubMedDate not supplied

Freezing affects the activity and subcellular distribution profile of human placental xenobiotic- and steroid-metabolizing enzymes.

Human placentae from both smoking and non-smoking mothers were examined with respect to the activity and apparent subcellular distribution of cytochrome P-450-linked xenobiotic-and steroid-metabolizing activities. Freezing of the placental sample in pieces before preparing mitochondria and microsomes led to decreases in some catalytic activities and changed the distribution profile of activities between mitochondria and microsomes. Cholesterol side-chain cleavage enzyme and aryl hydrocarbon hydroxylase were especially sensitive to the destructive effect of freezing. Activities in the microsomes were apparently more sensitive to freezing than were those in the mitochondrial fraction. In addition to the destruction of activities by freezing, cross-contamination of microsomes and mitochondria was postulated. Freezing tended to level off the differences between induced and uninduced material. In JEG cells, the specific activities of xenobiotic-metabolizing enzymes were higher in the mitochondrial fraction. In liver biopsy samples the expected, principally microsomal, localization of xenobiotic-metabolizing enzymes was observed. It is suggested that the placenta should be processed fresh at least as far as the postmitochondrial supernatant before freezing to avoid the destructive and cross-contaminating effects of freezing.

Cell Line↗