Autophagic vacuoles produced in vitro. I. Studies on cultured macrophages exposed to chloroquine.

Mouse macrophages exposed to 30 microg/ml of chloroquine in vitro develop autophagic vacuoles containing various cytoplasmic components and acid phosphatase. The early toxic vacuoles appear in the perinuclear region within 15 min; on electron microscopy, they show irregular shape, amorphous moderately dense content, apparent double membranes, and in some instances curved thin tubular extensions with a central, dark linear element. Cytoplasmic structures are probably transported into the vacuoles by invagination of the vacuolar membrane. After exposure to chloroquine for 1-4 hr, macrophages display large vacuoles containing degraded cytoplasmic structures, membranous whorls, and amorphous material. When chloroquine is removed by changing the culture medium after 4 hr, the cells survive and 24 hr later they exhibit no abnormality except for large cytoplasmic dense bodies packed with membrane lamellae. During recovery chloroquine disappears from the cells. 24 hr after exposure to chloroquine the macrophages have accumulated less hydrolases than control cells.