ENDOCYTOSIS OF CIGARETTE-SMOKE CONDENSATE BY RABBIT ALVEOLAR MACROPHAGES INVITRO MEASURED AS FLUORESCENCE INTENSITY

It has previously been shown that alveolar macrophages (AMs) from smokers have increased fluorescence compared to AMs from nonsmokers. In the present investigation, AMs lavaged from rabbits were exposed to a cigarette-smoke condensate (CSC) in order to study its influence on the fluorescence of AMs. Flow cytofluorometry was used. Alveolar cells exposed to 0.01% of CSC showed a fluorescence which increased with higher concentrations of the CSC. Incubation with CSC for 5 min was enough to give a significant rise (p < 0.001) in cell fluorescence compared to controls. After incubating fluorescent cells with untreated nonfluorescent AMs, fluorescent material was distributed to the non-fluorescent AMs within 30 min. Furthermore, fluorescence decreased when exposed cells were cultured in CSC-free medium. When incubating CSC with blood leucocytes, an almost threefold increase in fluorescence was observed among the phagocytic cells at 37-degrees-C compared to 4-degrees-C, whereas the fluorescence in the nonphagocytic cell population only showed a minor enhancement. Endocytosis of fluorescent material in CSC can explain the strong fluorescence seen in AMs from smokers. Exocytosis and re-endocytosis of the material by new AMs may explain the slow decline in the fluorescence of AMs observed after cessation of smoking.