Lysosomes hepatocytic

Goldfischer, S., B. Schiller, and I. Sternlieb. 1970. Copper in hepatocyte lysosomes of the toad, Bufo marinus L. Nature 228 172-173. 

The intracellular localization of carboxylesterases is predominantly microsomal, the esterases being localized in the endoplasmic reticulum [73] [79] [93], They are either free in the lumen or loosely bound to the inner aspect of the membrane. The carboxylesterases in liver mitochondria are essentially identical to those of the microsomal fraction. In contrast, carboxylesterases of liver lysosomes are different, their isoelectric point being in the acidic range. Carboxylesterase activity is also found in the cytosolic fraction of liver and kidney. It has been suggested that cytosolic carboxylesterases are mere contaminants of the microsomal enzymes, but there is evidence that soluble esterases do not necessarily originate from the endoplasmic reticulum [94], In guinea pig liver, a specific cytosolic esterase has been identified that is capable of hydrolyzing acetylsalicylate and that differs from the microsomal enzyme. Also, microsomal and cytosolic enzymes have different electrophoretic properties [77]. Cytosolic and microsomal esterases in rat small intestinal mucosa are clearly different enzymes, since they hydrolyze rac-oxazepam acetate with opposite enantioselectivity [95], Consequently, studies of hydrolysis in hepatocytes reflect more closely the in vivo hepatic hydrolysis than subcellular fractions, since cytosolic and microsomal esterases can act in parallel. 

Kagedal, K., Bironaite, D., and Olhnger, K., 1999, Anthraquinone cytotoxicity and apoptosis in primary cultures of hepatocytes. Free Rad. Res. 31 419-428 Kagedal, K., Johansson, U., and Olhnger, K., 2001, The lysosomal protease cathepsin D mediates apoptosis induced by oxidative stress. FASEB J. (May 18, 2001) 10.1096/. 00-0708fje... 

Monney, L., Ohvier, R., Otter, 1., Jansen, B., Poirier, GG., and Bomer, C., 1998, Role ofan acidic compartment in tumor-necrosis-factor-a-induced production of ceramide, activation of caspase-3 and apoptosis. Eur. J. Biochem. 251 295-303 Morrison, H., Jemstrom, B., Nordenskjdld, M., Thor, H., and Orrenius, S., 1984, Induction of DNA damage by menadione (2-methyl-l,4-naphthoquinone) in primary cultures of rat hepatocytes. Biochem. Pharmacol. 33 1763-1769 Neuzil, J., Svensson, 1., Weber, T, Weber, C., and Brunk, U.T., 1999, alpha-tocopheryl succinate-induced apoptosis in Jurkat T cells involves caspase-3 activation, and both lysosomal and mitochondrial destabilisation. FEES Lett. 445 295-300 Ngo, E.O., Nutter, L.M., Sura, T., and Gutierrez, P. L., 1998, Induction ofp53 by the... 

The liver eliminates proteins on first pass after oral administration and on each pass of hepatic blood flow. Hepatocytes, Kupffer cells, adipocytes, and endothelial cells can all be involved in proteolysis (Figure 5.6). Proteolysis can occur in lysosomes after endocytosis of a protein and lysosomal fusion. Endocytosis of a protein may be a nonspecific or receptor-mediated process. Proteolytic products are eliminated from the liver through biliary excretion, and subsequently digested further in the intestinal tract. 

Three-month inhalation exposure to zwcto-xylene (1000 ppm [4340 mg/m ], 6 h per day on five days per week) of male Wistar rats had a very slight effect on the hepatocyte ultrastructure limited proliferation of smooth endoplasmic reticulum and lysosomes was observed. Findings were similar after six months exposure to 100 ppm [434 mg/m ]. Simultaneous exposure to toluene made the proliferation of smooth endoplasmic reticulum more prominent (Rydzynski et al., 1992). 

The majority of body iron is not chelatable (iron from cytochromes and hemoglobin). There are two major pools of chelatable iron by DFO (19). The first is that delivered from the breakdown of red cells by macrophages. DFO competes with transferrin for iron released from macrophages. DFO will also compete with other plasma proteins for this iron, when transferrin becomes saturated in iron overload. The quantity of chelatable iron from this turnover is 20mg/day in healthy individuals and iron chelated from this pool is excreted in the urine (19). The second major pool of iron available to DFO is derived from the breakdown of ferritin and hemosiderin. The ferritin is catabolized every 72 hours in hepatocytes, predominantly within lysosomes (I). DFO can chelate iron that remains within lysosomes shortly after ferritin catabolism or once this iron reaches a dynamic, transiently chelatable, cytosolic low-molecular-weight iron pool (20). Cellular iron status, the rate of uptake of exogenous iron, and the rate of ferritin catabolism are influent on the level of a labile iron pool (21). Excess ferritin and... 

Seglen PO, Gordon PB, Poli A. Amino acid inhibition of autophagic/lysosomal pathway of protein degradation in isolated rat hepatocytes. Biochim Biophys Acta 1980 630 103-118. 

In certain cell types (e.g., fibroblasts) from patients with I-cell disease, lysosomal enzymes are secreted into the extracellular milieu rather than targeted to lysosomes. In contrast, other cells (such as hepatocytes, Kupffer cells, and leukocytes) contain nearly normal levels of lysosomal enzymes, even though these cells are also deficient in phosphotransferase activity. What do these observations suggest about the targeting of lysosomal enzymes in these different kinds of cells ... 

---