Iron and ferritin contents and distribution in human alveolar macrophages

Abstract

Previous investigations have shown that alveolar macrophages from cigarette smokers contain more iron than do macrophages obtained from nonsmokers. To localize intracellular iron and to help assess its potential for participation in the production of hydroxyl radicals, macrophages were fractionated and the ferritin and iron contents were measured in various cell fractions. Alveolar macrophages from seven smokers and six nonsmokers were lysed by nitrogen cavitation and centrifuged, first at 500 g and then at 11,000 g. Measured by radio-immunoassay, the total cellular ferritin was 133.8 +/- 33.2 ng and 782.0 +/- 177.8 ng per 1 x 10(6) macrophages (mean +/- SEM, p less than 0.01) obtained from nonsmokers and smokers, respectively. The total cellular iron contents were 7.5 +/- 0.6 nmol and 27.6 +/- 4.8 nmol per 1 x 10(6) macrophages (p less than 0.02) obtained from nonsmokers and smokers, respectively. The accumulation of iron by smokers' alveolar macrophages correlated with the number of cigarettes that had been smoked. Forty-two percent of the iron but only 9% of the ferritin was contained in the pellet obtained from centrifugation at 500 g. The pellet from the second centrifugation contained approximately 33% of the iron and 5% of the ferritin. The supernatant resulting from the second centrifugation contained 25% of the iron and 85% of the ferritin. Cigarette smoking did not appear to alter the intracellular distribution of either iron or ferritin. The ferritin content of bronchoalveolar lavage fluid was 0.10 +/- 0.04 micrograms/mg and 0.90 +/- 0.18 micrograms/mg albumin for nonsmokers and smokers, respectively (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)