Comparative study of the effect of aflatoxin and some antitumour antibiotics on rat liver lysosomes in vivo and in vitro

The alpha 1-macroglobulin-proteinase complex endocytosed into rat liver lysosomes was purified by a series of column chromatographic steps on concanavalin A-Sepharose, Sephacryl S-300, DEAE-cellulose and TSK gel DEAE-5PW columns. The complex contained no detectable alpha 2-macroglobulin. Studies on the substrate specificity indicated that the complex had tryptase-like activities towards various synthetic substrates, but no elastase, chymotrypsin, cathepsin-B and cathepsin-L activities. The proteinase activity was completely inhibited by di-isopropyl fluorophosphate, leupeptin and antipain, indicating that the proteinase bound to alpha 1-macroglobulin is a serine proteinase. Two protein bands (62 and 59 kDa) of the complex were labelled with [3H]diisopropyl fluorophosphate and both bands cross-reacted with anti-(mast-cell tryptase)antibody. These results suggest that mast-cell tryptase is a major targeting proteinase for alpha 1-macroglobulin in vivo. The main alpha-macroglobulin-proteinase complex in the adjuvant-treated rats was also the alpha 1-macroglobulin-tryptase complex, even though the plasma level of alpha 2-macroglobulin was elevated.

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On the localisation of d-tubocurarine in rat liver lysosomes in vivo by electron microscopy and subcellular fractionation

Naunyn-Schmiedeberg s Archives of Pharmacology ◽

10.1007/bf00499979 ◽

1975 ◽

Vol 289 (3) ◽

pp. 251-256 ◽

Cited By ~ 17

Author(s):

Jeanette G. Weitering ◽

Gerard J. Mulder ◽

Dirk K. F. Meijer ◽

Wim Lammers ◽

Maarten Veenhuis ◽

...

Keyword(s):

Electron Microscopy ◽

Rat Liver ◽

Subcellular Fractionation ◽

Liver Lysosomes ◽

Rat Liver Lysosomes

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The effect of Trypan Blue, suramin and aurothiomalate on the breakdown of 125I-labelled albumin within rat liver lysosomes

Biochemical Journal ◽

10.1042/bj1210021 ◽

1971 ◽

Vol 121 (1) ◽

pp. 21-26 ◽

Cited By ~ 41

Author(s):

Malcolm Davies ◽

J. B. Lloyd ◽

F. Beck

Keyword(s):

Rat Liver ◽

Trypan Blue ◽

Enzyme Inhibitors ◽

Protein Hydrolysis ◽

Particulate Carbon ◽

Liver Lysosomes ◽

Rat Liver Lysosomes

1. A fraction enriched in lysosomes was prepared by centrifugation from the livers of rats that had been injected 0.5h before death with 125I-labelled albumin. When suspended in sucrose-protected buffer, pH7.4, and incubated at 22°C for 2h, the particles progressively released iodotyrosine into the medium. Albumin digestion did not occur if the particles were subjected to treatments known to break lysosomes or if particles from uninjected rats were incubated in medium containing 125I-labelled albumin. It is concluded that the observed production of iodotyrosine results from protein hydrolysis within intact heterolysosomes. 2. Particles from rats pre-treated with Trypan Blue, suramin or aurothiomalate released iodotyrosine more slowly than controls. Since these compounds are enzyme inhibitors that concentrate in liver lysosomes after administration in vivo, their effect is ascribed to intralysosomal inhibition of proteolysis. The doses used did not decrease endocytosis of albumin into liver or cause increased lysosome breakage during incubation, thus allowing some alternative explanations of the decreased proteolysis to be eliminated. Particulate carbon, a non-inhibitor that also concentrates in lysosomes, did not affect albumin hydrolysis.

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