Binding of Sulfhydryl Reagents to Normal and Irradiated Leucocyte Lysosomes

Abstract

Summary The cytoplasmic granules (lysosomes) of leucocytes are highly reactive in situ, undergoing explosive rupture during phagocytosis, and relatively radiosensitive in the isolated state. The possibility that these properties might be related to membrane sulfhydryl groups was investigated by standard the binding of 203Hg‐labelled HgCL2 and p‐chloromercuribenzenesulfonate to granules isolated from rabbit peritoneal‐exudate neutrophils. Leucocyte lysosomes had a maximum mercury‐binding capacity of 1·92×10−7moles/mg. protein (7·5 × 10−17 moles per “average” granule), p‐chloro‐mercuribenzenesulfonate binding at 6·6 × 10−4 M was similar to this figure, but at lower concentrations binding of the mercurial was approx. 25% less than that of mercury. Binding of p‐chloromercurihenzenesulfonate was influenced by the physical state of the preparations as well as by the ionic composition of the suspending medium. Isolated granules were highly sensitive to mercury and p‐chloromencuribenzenesulfonate, undergoing rapid disruption upon incubation at 28° in the presence of low concentrations of these agents. At high concentrations of mercury (but not of p‐chloromercuribenzeuesulfonate) the granules became increasingly resistant to rupture. Lysosomes were more sensitive to gammaradiation when they were irradiated in the presence of 10 −5 M HgCl2, indicating that sulfhydryl groups may be involved in the rupture of the granules by radiation.