Sensitivity of human placental monooxygenase activity to maternal smoking

Clin Pharmacol Ther. 1981 Nov;30(5):687-92. doi: 10.1038/clpt.1981.221.


The in vitro oxidation of 7-ethoxyresorufin was studied in placental microsomes from 47 full-term pregnancies. Placental activities were compared in four groups formed on the basis of maternal smoking history as follows: nonsmokers (n = 12), passive smokers (n = 16), 1 to 20 cigarettes/day (n = 13), and 20+ cigarettes/day (n = 5). Passive smoking was defined as living with someone who smoke cigarettes. Umbilical cord plasma thiocyanate concentrations were measured to confirm histories and were higher when mothers smoked (80 +/- 10 micro M, 1 to 20 cigarettes/day, 116 +/- 8 micro M, 20+ cigarettes/day) than when mothers did not smoke (34 +/- 3 micro M, nonsmokers; 35 +/- 3 micro M, passive smokers). 7-Ethoxyresorufin O-deethylase activity was increased 10- to 30-fold in placentas from smokers. Activity toward 7-ethoxyresorufin in placentas from smokers was markedly inhibited in vitro by addition of 7,8-benzoflavone. Among nonsmokers, percent inhibition of O-deethylase activity by 7,8-benzoflavone was greater (P less than 0.05) in placentas from women passively exposed to cigarette smoke. Human placental monooxygenase activity is sensitive to both active and passive cigarette smoke exposure.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Benzoflavones / pharmacology
  • Cytochrome P-450 CYP1A1
  • Female
  • Humans
  • Oxidoreductases / analysis
  • Oxygenases / analysis*
  • Placenta / enzymology*
  • Pregnancy
  • Tobacco Smoke Pollution
  • Tobacco Use Disorder / enzymology*


  • Benzoflavones
  • Tobacco Smoke Pollution
  • alpha-naphthoflavone
  • Oxidoreductases
  • Oxygenases
  • Cytochrome P-450 CYP1A1