FIGURE 4.

Activation of lysosomal P2X4 under physiological conditions. A, schematic diagram showing measurement of ATP concentration in the lysosomal fraction and methods used to estimate ATP concentration in lysosome lumen. B, yield of lysosome isolation was determined by measuring the ratio of Lamp1 band intensity in fraction G over that in whole cell lysate. C, activation of lysosomal P2X4 by alkalization of intraluminal pH. NH₄Cl induced currents were compared with the basal currents before NH₄Cl application. D, summary of currents elicited by NH₄Cl in enlarged lysosomes dialyzed with 0.1 and 2 mm ATP in pH 4.6 Tyrode.