scholarly journals Immunocytochemical localization of the receptor for asialoglycoprotein in rat liver cells.

1982 ◽  
Vol 92 (3) ◽  
pp. 865-870 ◽  
Author(s):  
H J Geuze ◽  
J W Slot ◽  
G J Strous ◽  
H F Lodish ◽  
A L Schwartz
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Golgi Complex ◽  
Blood Cells ◽  
Liver Cells ◽  
Frozen Sections ◽  
Capillary Membrane ◽  
Intracellular Receptor ◽  
Rat Liver Cells ◽  
Ultrathin Frozen Sections

We used high-resolution immunocytochemistry on ultrathin frozen sections labeled with colloidal gold to study the subcellular distribution of the asialoglycoprotein receptor in rat liver. The receptor was localized along the entire hepatocyte plasma membrane, including the bile capillary membrane, but was scarce intracellularly. Sinusoidal lining (Kupffer) cells and blood cells showed no immunoreactivity. In liver cells of rats injected with 1 to 100 micrograms of asialoorosomucoid (ASOR) 2-15 min before tissue fixation, endocytotic internalization of receptors at the blood front was conspicuous. At all times in this interval, receptor was present in approximately 100-nm vesicles and larger vacuoles adjacent to the sinusoidal plasma membrane. No other significant intracellular receptor was noted during the 15-min exposure to ASOR; in particular, lysosomes and Golgi complex were not labeled. Our observations, in combination with data from the literature which demonstrate that, under these conditions, the ligand is transferred further to the Golgi complex-lysosome region, suggest that the receptor and ligand are dissociated in the vicinity of the plasma membrane, after which the receptor rapidly returns to the cell surface.

scholarly journals Study of fluxes at low concentrations of l-tri-iodothyronine with rat liver cells and their plasma-membrane vesicles. Evidence for the accumulation of the hormone against a gradient

1981 ◽  
Vol 198 (3) ◽  
pp. 457-466 ◽  
Author(s):  
Govind S. Rao ◽  
Marie Luise Rao ◽  
Astrid Thilmann ◽  
Hans D. Quednau
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Liver Homogenate ◽  
Membrane Vesicles ◽  
Liver Cells ◽  
Free Form ◽  
Plasma Membrane Vesicles ◽  
Cytosol Fraction ◽  
Low Concentrations ◽  
Rat Liver Cells

1. Influx and efflux of l-tri-[125I]iodothyronine with isolated rat liver parenchymal cells and their plasma-membrane vesicles were studied by a rapid centrifugation technique. 2. At 23°C and in the concentration range that included the concentration of free l-tri-iodothyronine in rat plasma (3–5pm) influx into cells was saturable; an apparent Kt value of 8.6±1.6pm was obtained. 3. At 5pm-l-tri-[125I]iodothyronine in the external medium the ratios of the concentrations inside to outside in cells and plasma-membrane vesicles were 38:1 and 366:1 respectively after 7s of incubation. At equilibrium (60s at 23°C) uptake of l-tri-[125I]iodothyronine by cells was linear with the hormone concentration, whereas that by plasma-membrane vesicles exhibited an apparent saturation with a Kd value of 6.1±1.3pm. 4. Efflux of l-tri-[125I]iodothyronine from cells equilibrated with the hormone (5–123pm) was constant up to 21 s; the amount that flowed out was 17.7±3.8% when cells were equilibrated with 5pm-hormone. When plasma-membrane vesicles were equilibrated with l-tri-[125I]iodothyronine (556–1226pm) 66.8±5.8% flowed out after 21 s. 5. From a consideration of the data on efflux from cells and binding of l-tri-[125I]iodothyronine to the liver homogenate, as studied by the charcoal-adsorption and equilibrium-dialysis methods, it appears that 18–22% of the hormone exists in the free form in the cell. 6. Vinblastine and colchicine diminished the uptake of l-tri-[125I]iodothyronine by cells but not by plasma-membrane vesicles; binding to the cytosol fraction was not affected. Phenylbutazone, 6-n-propyl-2-thiouracil, methimazole and corticosterone diminished the uptake by cells, plasma-membrane vesicles and binding to the cytosol fraction to different extents. 7. These results suggest that at low concentrations of l-tri-[125I]iodothyronine rat liver cells and their plasma-membrane vesicles accumulated the hormone against an apparent gradient by a membrane-mediated process. Contribution of cytoplasmic proteins to uptake by plasma-membrane vesicles was negligible. The amount of l-tri-[125I]iodothyronine required to achieve half-maximal uptake agrees with that occurring in the free form in the blood, conferring physiological importance to the transporting system in the plasma membrane of the liver cell.

scholarly journals Localization and biosynthesis of NADH-cytochrome b5 reductase, an integral membrane protein, in rat liver cells. I. Distribution of the enzyme activity in microsomes, mitochondria, and golgi complex.

1980 ◽  
Vol 85 (3) ◽  
pp. 501-515 ◽  
Author(s):  
N Borgese ◽  
J Meldolesi
Keyword(s):  
Cytochrome C ◽  
Rat Liver ◽  
Golgi Complex ◽  
Cytochrome B5 ◽  
Liver Cells ◽  
Cytochrome C Reductase ◽  
Cytochrome B5 Reductase ◽  
Galactosyl Transferase ◽  
Rat Liver Cells ◽  
Nadh Cytochrome

The subcellular distribution of NADH-cytochrome b5 reductase in rat liver cells was reinvestigated. In fresh heavy and light Golgi fractions (GF3 and GF1 + 2) and in mitochondria, the specific activity of rotenone-insensitive NADH-cytochrome c reductase was approximately 100, 60, and 30%, respectively, of the value found in microsomes. However, the Golgi enzyme was unstable inasmuch as pelleting and resuspending the fresh fractions resulted in a considerable inactivation (40--60%), which was further increased with subsequent storage at 4 degrees C. A similar inactivation was observed using cytochrome b5 but not ferricyanide as electron acceptor. The inactivation of Golgi NADH-cytochrome c reductase activity was independent of the protein concentration of the fractions during storage, was unaffected by the addition of the antioxidant butylated hydroxytoluene, but was partly prevented by buffering the fractions at neutral pH and by storage at--20 degrees C. A total Golgi fraction was analyzed by density equilibration on continuous sucrose gradients after exposure to digitonin. As expected, the distribution of both protein and galactosyl transferase were shifted to higher densities by this treatment. However, not all galactosyl transferase-bearing elements were shifted to the same extent by exposure to the detergent, suggesting a biochemical heterogeneity of the Golgi complex. In contrast to their behavior in microsomes, the distribution of NADH-cytochrome c reductase and cytochrome b5 of Golgi fractions was shifted by digitonin, although to a lesser extent than that of galactosyl transferase. These results indicate that NADH-cytochrome b5 reductase is an authentic component of Golgi membranes, as well as of microsomes and of mitochondria. The conflicting results reported in the past on the Golgi localization of the enzyme could be due, on the one hand, to the differential lability of the activity in its various subcellular locations and, on the other, to the heterogeneity of the Golgi complex in terms of both cholesterol and enzyme distribution.

Hormone-Calcium Interactions with the Plasma Membrane of Rat Liver Cells

Science ◽  
1972 ◽  
Vol 176 (4031) ◽  
pp. 175-177 ◽  
Author(s):  
L. Shlatz ◽  
G. V. Marinetti
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Liver Cells ◽  
Rat Liver Cells

Studies on the template activity of ‘isolated’ Xenopus erythrocyte nuclei. II. The effects of cytoplasmic extracts

1977 ◽  
Vol 24 (1) ◽  
pp. 119-129
Author(s):  
N. Maclean ◽  
V.A. Hilder
Keyword(s):  
Molecular Weight ◽  
Genetic Control ◽  
Rat Liver ◽  
Blood Cells ◽  
Rna Synthesis ◽  
Liver Cells ◽  
Template Activity ◽  
Rat Liver Cells

The effects of exposing nuclei isolated from Xenopus erythrocytes to cytoplasmic extracts prepared from various sources on their template activity are described. The cytoplasm of rat liver cells and the immature blood cells of Xenopus contain factors which stimulate RNA synthesis in these essentially inactive nuclei, whereas the cytoplasm of many other cells does not yield such factors. The active factors in rat liver cytoplasmic extracts appear to be proteins of molecular weight about 40000 Daltons. The implications of these results for genetic control in eukaryotes are discussed.

Decrease of calmodulin and actin in the plasma membrane of rat liver cells during proliferative activation

1990 ◽  
Vol 173 (3) ◽  
pp. 1287-1291 ◽  
Author(s):  
Cristina Pujades ◽  
Ricardo Bastos ◽  
Carlos Enrich ◽  
Oriol Bachs
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Liver Cells ◽  
Rat Liver Cells
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