MAO A AND B RADIOTRACERS SHOW A REDUCED ARTERIAL PLASMA INPUT FUNCTION, PROLONGED LUNG RETENTION AND REDUCED MAO IN SMOKERS vs NON-SMOKERS

摘要

We have previously shown that smokers have reduced human brain monoamine oxidase A and B (MAO A and B) using PET and the irreversible mechanism-based radiotracers [~11C]clorgyline and [~11C]deprenyl (CLG and DEP) and their deuterium-substituted derivatives (D CLG, D DEP) (Fowler er al., 1996). We also compared MAO in peripheral organs in non-smokers and smokers using the deuterium isotope effect to assess specificity for MAO. In applying a three-compartment model to time-activity data for the lung, we found that smokers had reduced k3, the model term proportional to MAO activity, even though the lung uptake at plateau was similar for the two groups. To investigate the factors contributing to a reduced value of k3 even when the plateau phase of the time-activity curves were similar, we re-examined the radiotracer kinetics and the robustness of the model term k3 for estimating lung MAO A and B. Methods: Time-activity data from lung and arterial plasma over a 60 min study time were used from 7 non-smokers and 7 smokers scanned with CLG and D CLG and 5 non-smokers and 9 smokers scanned previously with DEP and D DEP (Fowler et al., 2003). The integrals for the arterial plasma time-activity curves were compared at an early time point (2.5 min) and at the end of the study (55 min).