Abstract
Summary
The effects of zinc, certain other metals (Cu, Hg, Pb, Cd, Ni and Au), 8-hydroxyquinoline (8-HQ), and various stoichiometric complexes of Zn:8-HQ on the release of β-glucuronidase from lysosomes isolated from rat liver were tested. Zinc and Zn:8-HQ (1:1 and 1:2 complexes) markedly stabilized lysosomes in a concentration-related fashion. The saturated 1:3 complex and 8-HQ alone showed a labilizing effect, while the nonchelating substitute of 8-HQ (8-methoxyquinoline) did not affect lysosomal stability. Cd and Pb also stabilized lysosomes, although they were both less effective than zinc.
The distribution of zinc between the membrane and the interior of isolated liver lysosomes is 2:1. After treatment with zinc, the distribution is unchanged but the total content of zinc increased 10-fold. In samples treated with unsaturated complexes of Zn:8-HQ (1:1 or 1:2) the total amount of zinc present is the same as in zinc-treated particles, but the metal is bound exclusively to the membrane fraction.
The effect of pH on lysosomal fragility in the presence of zinc was almost opposite to that observed when calcium was tested. The results of this study favor the concept that the stabilizing effect of zinc occurs at the surface of the membrane. The effect does not seem to be related to the function of known phospholipases.
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