FIG. 5.

LY is released from endosomes upon exposure of cells to porin. LY was loaded into the endosomes of A431 cells as described in Materials and Methods. Cultures were stimulated for 5 min at 18°C with Ca²⁺-replete (+) or Ca²⁺-depleted (−) medium (M) or with medium containing P1.B. Certain cultures, as indicated, were stimulated with P1.B that had been preincubated with 0.1 mM ATP. LY in the medium was monitored by determining the fluorescence of the samples (excitation wavelength, 485 nm; emission wavelength, 538 nm). The amount of LY released into the medium upon exposure to P1.B was expressed as the percentage of total LY taken up by cells in control wells (LY level in cultures stimulated with P1.B in Ca²⁺-replete medium, 10.36 ± 1.88; P < 0.01, paired Student's t test).