Stimulation of the release of lysosomal and nonlysosomal granular enzymes from macrophages treated with monensin.

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Abstract
Mouse peritoneal macrophages that had been treated with a monovalent carboxylic ionophore, monensin, selectively secreted lysosomal and nonlysosomal granular enzymes into the medium. When macrophages were incubated with 1 to 10 μM monensin, the release of β-glucuronidase, β-hexo-saminidase and β-galactosidase was stimulated time and does dependently. Neither the β-glucosidase nor acid phosphatase, enzymes bound to the lyso-somal membranes, however, were released by monensin. Neutral α-glucosidase, shown recently to be localized in nonlysosomal granules of macrophages (15), was released by monensin at concentrations lower than those required for lysosomal enzyme release. Increased release of lysosomal enzymes also took place in a manner similar to that seen with monensin-treated macrophages after treatment of macrophages with weak bases, chloroquine and ammonium chloride. Neutral α-glucosidase, however, was not released when chloroquine was present in concentrations that stimulated the release of lysosomal enzymes. The UDP-galactosyltransferase activity of the Golgi apparatus in the macrophages markedly decreased after treatment with low concentration of monensin.