Effects of experimental marijuana and tobacco smoke inhalation on alveolar macrophages. A comparative stereologic study.

Male rats were exposed for 30 consecutive days to whole smoke from either marijuana or tobacco cigarettes. At the end of this period, anesthetized animals from the two smoke-exposed groups together with their age-matched, nonexposed controls underwent bronchopulmonary lavage, and the free lung cells obtained were fixed and collected for light and electron microscopy. Measurements made on 1-micrometer. sections indicated slight, but statistically nonsignificant, shifts in the frequency distributions of alveolar macrophage profile diameters after both exposure regimens. Stereologic techniques were used to study the subcellular morphology of alveolar macrophages from the three groups of animals. Statistically significant changes were found in cells from tobacco-exposed animals in the volume densities of mitochondria, lipid inclusions, lysosomes, remaining cytoplasm, and the surface to volume ratio of the cell. In contrast, only two parameters in the cells from marijuana-exposed animals were found to have changed significantly, with a 3-fold increase in the volume density of lipid inclusions and a slight reduction in the volume density of the remaining cytoplasm. Possible reasons for the differences in the response of the cells in the two smoke-exposed groups are discussed.