Fig. 10. Non-lamellar, cholesterol-rich LAMP-2-positive vacuoles are acidic, lysosomal organelles. M9 cells were grown in regular medium (A-C,G-I) or in media supplemented with 10 mM 3-MA for 3 days (D-F,J-L) and selected cultures were incubated with U18666A for the final 24 hours (G-L). Viable cells were labelled with Lysotracker Red (A,D,G,J) and after fixation, with filipin (B,E,H,K). Merged images (C,F,I,L) show Lysotracker Red in red and filipin in blue. The large cholesterol-rich swollen lysosomal vacuoles induced by U18666A are still acidic in the presence of 3-MA. Bar, 5 µm.