[Effects of cigarette smoking on I-123 IMP clearance from the lung]

N-isopropyl-p-I-123-iodoamphetamine (I-123 IMP), originally developed as a brain scanning agent, is also taken up by the lung. To evaluate the cigarette smoking on the uptake of IMP by the lung, we studied I-123 IMP clearance from the lung of 14 volunteers; 5 non-smokers and 9 smokers. After the injection of 111 MBq (3 mCi) of I-123 IMP into the medial cubital vein, the time-activity curve for 60 minutes and the regional activity using 1 frame per minute and a 64 x 64 matrix was obtained. 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 significant correlations between k1, k2, and the number of cigarettes smoked per day were found. In conclusion, this study suggests that the delayed clearance and retention of I-123 IMP in the lung indicate the lung metabolic disorders due to cigarette smoking.