Human Anatomy and Physiology, ed 2

Several studies have documented a strong association between smoking and depression. Because ciga- rette smoke has been reported to inhibit monoamine oxidase (MAO) A in vitro and in animals and because MAO A inhibitors are effective antidepressants, we tested the hypoth- esis that MAO A would be reduced in the brain of cigarette smokers. We compared brain MAO A in 15 nonsmokers and 16 current smokers with ( 11 C)clorgyline and positron emis- sion tomography (PET). Four of the nonsmokers were also treated with the antidepressant MAO inhibitor drug, tranyl- cypromine(10mgydayfor3days)afterthebaselinePETscan andthenrescannedtoassessthesensitivityof( 11 C)clorgyline binding to MAO inhibition. MAO A levels were quantified by using the model term lk3which is a function of brain MAO A concentration. Smokers had significantly lower brain MAO A than nonsmokers in all brain regions examined (average reduction, 28%). The mean lk3values for the whole brain were 0.18 6 0.04 and 0.13 6 0.03 ccbrain (mlplasma) 21 min 21 for nonsmokers and smokers, respectively; P < 0.0003). Tranyl- cypromine treatment reduced lk3by an average of 58% for the different brain regions. Our results show that tobacco smoke exposureisassociatedwithamarkedreductioninbrainMAOA, and this reduction is about half of that produced by a brief treatment with tranylcypromine. This suggests that MAO A inhibition needs to be considered as a potential contributing variable in the high rate of smoking in depression and in the development of more effective strategies for smoking cessation.

Brain monoamine oxidase A inhibition in cigarette smokers

The present paper is a review of up-to-date findings on vitamin A transport from intestines to target-cell and metabolism of this fat-soluble vitamin. The hypotheses of possible enzymes participation in the process of etherification/hydrolysis and oxidation/reduction of vitamin A are discussed. Furthermore, possible roles of cellular retinoid-binding proteins in the process of vitamin A transport and metabolism are reviewed.

Izel Fourie Sørensen

Papers

Influence of tobacco smoke constituents on monoamine oxidase activity in vitro and on human placental monoamine oxidase A activity in vivo