EFFECTS OF CIGARETTE-SMOKING ON I-123 N-ISOPROPYL-P-IODOAMPHETAMINE CLEARANCE FROM THE LUNG

Iodine 123 N-isopropyl-p-iodoamphetamine (I-123-IMP), originally developed as a brain scanning agent, is also taken up by the lung. To evaluate the effects of cigarette smoking on the kinetics of IMP in the lung, we studied I-123-IMP clearance from the lung in 18 volunteers (8 non-smokers and 10 smokers). After the injection of 111 MBq of I-123-IMP into the medial cubital vein, the time-activity curve for 60 min and the regional activity using 1 frame per minute and a 64 x 64 matrix were obtained. The I-123-IMP clearance curve was described as follows: C(t) = A1e(-k1t) + A2e(-k2t) (A1, A2: intercepts, and k1, k2: slopes of the exponential components). I-123-IMP clearance was delayed in smokers, and k2 was smaller in smokers. Also, a correlation between k1, k2, and the number of cigarettes smoked per day was found (r = -0.65, r = -0.74, respectively, P < 0.01). In conclusion, this study suggests that the delayed clearance and retention of I-123-IMP in the lung indicate lung metabolic disorders due to cigarette smoking.