ATP is stored in LBs. (A) Staining of primary ATII cells with quinacrine and LTR (a marker for LBs), indicating the presence of intravesicular ATP in LBs (arrowheads). Bar, 10 µm. (B) ATII cells were incubated with mant-ATP for 1 h and labeled with LTR. Mant-ATP is enriched in LBs (arrowheads). Bar, 10 µm.