The role of placental carbonyl reducing enzymes in biotransformation of bupropion and 4-methylnitrosamino-1-(3-pyridyl)-1-butanone

Valentina M. Fokina, Svetlana L. Patrikeeva, Cheryl Oncken, Gary D.V. Hankins, Mahmoud S. Ahmed, Tatiana Nanovskaya

Research output: Contribution to journalArticlepeer-review


Background: Bupropion (BUP) has a potential to be an effective pharmacotherapy for smoking cessation during pregnancy. Smoking during pregnancy stimulates placental carbonyl reductases that catalyze the biotransformation of BUP. 4-methylnitrosamino-1-(3-pyridyl)-1-butanone (NNK) is a potent carcinogen of cigarette smoke. Carbonyl reduction of NNK into 4-methylnitrosamino-1-(3-pyridyl)-1-butanol (NNAL) constitutes a major step in NNK detoxification. Thus, placentas of pregnant smokers on BUP therapy can become a site of drug-drug interaction. Therefore, we investigated the effect of continuous exposure to BUP and cigarette smoke on the activity of placental carbonyl reductases in the formation of NNAL from NNK. Methods: The reductive metabolism of NNK was determined using microsomal and cytosolic subcellular fractions of placentas obtained from non-smoking women treated with BUP for depression, and women not exposed to BUP: non-smokers (control) and smokers. The effect of BUP and its metabolites on the reductive metabolism of NNK was investigated using subcellular fractions of control placentas. Results: The formation of NNAL from NNK by placental cytosolic fractions of heavy smokers (≥20 cigarettes per day) was lower than that of control (12.1±3.5 nmol.mgP-1 vs 16.5±6.0 nmol.mgP-1, P<0.05). While being exposed to BUP, the activity of placental carbonyl reductases remained unaffected, the formation of NNAL in the placental cytosolic fraction decreased only in the presence of high concentrations of BUP metabolites. Conclusion: Smoking during pregnancy decreases the detoxifying capacity of soluble carbonyl reductases towards NNK. Given the experimental conditions, exposure to BUP and its metabolites should not impede the reductive metabolism of NNK by placenta in vivo.

Original languageEnglish (US)
Pages (from-to)29-34
Number of pages6
JournalDrug Metabolism Letters
Issue number1
StatePublished - Mar 1 2017


  • Bupropion
  • Carbonyl reductases
  • NNAL
  • NNK
  • Placenta
  • Smoking

ASJC Scopus subject areas

  • Pharmaceutical Science
  • Clinical Biochemistry
  • Biochemistry, medical
  • Pharmacology (medical)


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