RESTON, Va.-- Smoking appears to reduce a key enzyme in the lungs, possibly contributing to some of smoking's deleterious health effects, according to a study published in the September issue of the Journal of Nuclear Medicine. The study, which used a radiotracer to track the enzyme, also shows that smokers had a lower concentration of the tracer in the bloodstream than nonsmokers did, leading to speculation that smokers and nonsmokers may respond differently to a variety of substances administered by inhalation or intravenously, including therapeutic, anesthetic and addictive drugs.

"The effects of smoking on human health are enormous; yet, little is known about the pharmacologic effects of smoking on the human body apart from the effects of nicotine," noted Joanna S. Fowler, Ph.D., program director of the Brookhaven Center for Translational Neuroimaging in Upton, N.Y. Researchers from Brookhaven National Laboratory, the National Institute on Drug Abuse and the State University of New York at Stony Brook used positron emission tomography (PET) scanning and a tracer chemical that binds to a specific form of the enzyme monoamine oxidase (MAO A) to track MAO A levels in both smokers and nonsmokers. With whole-body PET imaging, researchers could measure the concentration and movement of the radiotracer and MAO A, a subtype of the enzyme crucial to mood regulation and one that breaks down chemical compounds that elevate blood pressure, said the Society of Nuclear Medicine member.

In the study, "Comparison of Monoamine Oxidase A in Peripheral Organs in Nonsmokers and Smokers," researchers traced the MAO A subtype in nine smokers and nine nonsmokers, discovering that MAO A was fairly well "intact" in all of the peripheral organs except in smokers' lungs, said Fowler. Smokers had MAO A levels that were 50 percent lower than in nonsmokers, she said, noting that a prior study had also shown a significant reduction of MAO A in smokers' brains.

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Contact: Maryann Verrillo
mverrillo@snm.org
703-708-9000
Society of Nuclear Medicine
6-Sep-2005

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