Potassium ion dependent proton efflux and depolarization from spleen lysosomes

Lysosomes, isolated from various organs, exhibited an acidic interior (approximately equal to pH 5.2) when incubated in a buffer at neutral pH. K+-induced proton efflux was observed in spleen lysosomes, but not in liver or kidney lysosomes. The initial velocity of the proton efflux showed saturation kinetics with Km value of about 15 mM K+. Rb+ and Cs+ have an effect similar to K+, while Na+, Li+ or divalent cations have little or no effect. The properties of the K+ induced proton efflux correlated with the K+-induced depolarization of the lysosomes, suggesting the presence of K+-transport system(s) in lysosomal membranes.