Pulmonary retention of iodobenzyl-propanediamine in humans. Effect of cigarette smoking.

N,N,N'-trimethyl-N'-(2-hydroxy-3-methyl-5-iodobenzyl)-1,3-propanediamine (HIPDM), a synthetic basic compound with high affinity for lung tissue of various animal species, was labeled with 123I and injected into normal smokers (n = 9) and into asymptomatic smokers (n = 9). Time/activity curves were recorded for 90 min by gamma camera. HIPDM lung clearance was described by two exponential components. In smokers, the mean time of the first component, 10 +/- 1.4 min (mean +/- SEM), did not significantly differ from that of nonsmokers (9.7 +/- 0.9 min), whereas the mean time of the second component (12.9 +/- 0.6 h) was longer than that of nonsmokers (6.7 +/- 0.2 h). The intercept to the ordinate of the second exponential component was significantly higher in smokers (90.3 +/- 1.5%) than in nonsmokers (80.7 +/- 1.9%). Control studies in rabbits showed that, 2 min after intravenous injection, 95% of HIPDM is taken up by the lung; time/activity curves were similar to those obtained in humans. The longer pulmonary persistence of HIPDM in smokers may reflect an increased number of cellular binding sites or may be the expression of hindered HIPDM biotransformation. The rabbit can be used as a model to further investigate HIPDM kinetics in relation to lung dysfunction.