Abstract
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Objectives: To elucidate potential mechanisms underlying the slow release of nicotine from lung tissue and differences between dependent (DS) and non-dependent smokers (NDS) in the rate of nicotine washout from the lung tissue observed after cigarette smoking.
Methods: The chest of each of 18 DS and 10 NDS participants was scanned for 10 minutes after the i.v. administration of 260 MBq of [11C]-nicotine. The volume distribution of lung tissue (VT) was calculated using Logan analysis. The blood input function was obtained by the measurement of radioactivity in the right ventricle.
Results: At several seconds after administration, 72% of the injected dose was observed in the lungs. The time for the washout of 50% of the radioactivity (T1/2) from the lungs for DS (70 ± 11 sec) was significantly higher (P < 0.005) than that for NDS (23 ± 4 sec). The total volume distribution (VT) in the lungs (including air space and blood volume) in DS was almost two fold of that in NDS (1.46 ± 0.13 and 0.77 ± 0.05, respectively; P < 0.0001). There was a strong correlation between VT and washout T1/2 values (r = 0.78, P < 0.0001) and between VT and T1/2 of brain accumulation after inhalation of a single puff of cigarette smoke (r = 0.71, P < 0.005).
Conclusions: The high accumulation, slow release from the lungs, and difference in washout of nicotine in DS and NDS can be explained by high VT values for nicotine in lungs. Assuming that only 1/20th of total lung volume is represented by lung tissue the respective VT values for true lung tissue in DS and NDS are ca. 30 and 15.
Research Support: Philip Morris USA
- Society of Nuclear Medicine, Inc.