Study objectives: Cadmium (Cd) is a toxic metal associated with emphysema and lung cancer, which is present in both air pollution and cigarette smoke. Metallothionein (MT) is an inducible protein that binds and detoxifies cellular Cd. The goals of this study were to determine whether increased concentrations of Cd are present in alveolar macrophages (AMs) of cigarette smokers (CSMs) and to determine whether MT accumulated in response to the presence of Cd.
Design: AMs were recovered by BAL from 10 healthy nonsmokers (NSMs) and 10 CSMs. The Cd content of the AMs was determined by inductively coupled plasma-mass spectrometry, and the MT content was determined using a Cd/hemoglobin radioassay (with 109Cd).
Measurements: Cd was detected in AMs recovered from all subjects, with higher mean (± SEM) concentrations in CSMs compared with those in NSMs (3.4 ± 0.5 vs 1.3 ± 0.2 ng/106 cells; p < 0.005). There was a correlation between current smoking history (cigarettes per day) and the AM content of Cd (r = 0.74; p < 0.05). The mean AM content of MT was similar in NSMs (1.2 ± 0.2 μg/107 cells) and CSMs (1.0 ± 0.2 μg/107 cells).
Conclusions: AMs in CSMs accumulate significant amounts of Cd without a concurrent increase in MT content, indicating greater saturation of MT. Increased Cd burden in alveolar cells could contribute to the development of lung diseases in CSMs.