title: The effect of cytochalasin B on the release of lysosomal enzymes and intra-lysosomally-stored polyvinylpyrrolidone in the isolated perfused rat liver.
abstract: The uptake and subcellular distribution in vivo and release in vitro of 125I-polyvinylpyrrolidone (125I-PVP) has been studied in rat liver. Using the techniques of sucrose-density-gradient sedimentation and isopycnic centrifugation, it was shown that 4-15 days after injection of 125I-PVP the majority of the radioactivity was still in a high-molecular-weight form and associated with the lysosomes of the liver, the size and density properties of which were not significantly altered. Practically all of the 125I-PVP found in the lysosomes was free in the lumen and not associated with the lysosomal membrane, its intra-lysosomal distribution being much more similar to that of beta-galactosidase than arylsulphatase or beta-N-acetylglucosaminidase. In an isolated recirculating perfusion system the liver released all the enzymes studied (arylsulphatase, beta-galactosidase and lactate dehydrogenase) and, when previously loaded, 125I-PVP was also released into the perfusate. The magnitude of the release was always in the order 125I-PVP greater than beta-galactosidase greater than arylsulphatase. Preloading the lysosomes in vivo appeared to bring about an increase in the mean levels of release of all the enzymes, but the wide spread of data made this statistically significant only for lactate dehydrogenase. The microfilament poison cytochalasin B increased the release of arylsulphatase and beta-galactosidase, but not lactate dehydrogenase, in the perfused non-loaded livers, but failed to augment the release of any of the enzymes or 125I-PVP in the loaded livers. After perfusion, subcellular fractionation of the liver showed that the lysosomes had become enlarged and more fragile, especially so with those rich in 125I-PVP and beta-galactosidase rather than those rich in arylsulphatase and beta-N-acetylglucosaminidase.
mesh_terms: D000818:Animals; D001192:Arylsulfatases / Q000378:metabolism; D003571:Cytochalasin B / Q000494:pharmacology*; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D066298:In Vitro Techniques; D007457:Iodine Radioisotopes; D008099:Liver / Q000378:metabolism*; D008247:Lysosomes / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D011205:Povidone / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D007457:Iodine Radioisotopes; D003571:Cytochalasin B; D001192:Arylsulfatases; D001616:beta-Galactosidase; D011205:Povidone; D004121:Dimethyl Sulfoxide