Catabolism of uridine by endothelial cells, kupffer cells, and parenchymal cells of rat liver

Hepatic lipase (HL) is thought to be located at the vascular endothelium in the liver. However, it has also been implicated in the binding and internalization of chylomicron remnants in the parenchymal cells. In view of this apparent discrepancy between localization and function, we re-investigated the localization of HL in rat liver using biochemical and immunohistochemical techniques. The binding of HL to endothelial cells was studied in primary cultures of rat liver endothelial cells. Endothelial cells bound HL in a saturable manner with high affinity. However, the binding capacity accounted for at most 1% of the total HL activity present in the whole liver. These results contrasted with earlier studies, in which non-parenchymal cell (NPC) preparations had been found to bind HL with a high capacity. To study HL binding to the different components of the NPC preparations, we separated endothelial cells, Kupffer cells and blebs by counterflow elutriation. Kupffer cells and endothelial cells showed a relatively low HL-binding capacity. In contrast, the blebs, representing parenchymal-cell-derived material, had a high HL-binding capacity (33 m-units/mg of protein) and accounted for more than 80% of the total HL binding in the NPC preparation. In contrast with endothelial and Kupffer cells, the HL-binding capacity of parenchymal cells could account for almost all the HL activity found in the whole liver. These data strongly suggest that HL binding occurs at parenchymal liver cells. To confirm this conclusion in situ, we studied HL localization by immunocytochemical techniques. Using immunofluorescence, we confirmed the sinusoidal localization of HL. Immunoelectron microscopy demonstrated that virtually all HL was located at the microvilli of parenchymal liver cells, with a minor amount at the endothelium. We conclude that, in rat liver, HL is localized at the microvilli of parenchymal cells.

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The uptake and metabolism of chylomicron-remnant lipids by rat liver parenchymal and non-parenchymal cells in vitro

Biochemical Journal ◽

10.1042/bj2320395 ◽

1985 ◽

Vol 232 (2) ◽

pp. 395-401 ◽

Cited By ~ 6

Author(s):

P M Lippiello ◽

P J Sisson ◽

M Waite

Keyword(s):

Endothelial Cells ◽

Rat Liver ◽

Kupffer Cells ◽

Liver Cell ◽

Cholesterol Ester ◽

Cell Types ◽

Chylomicron Remnant ◽

Parenchymal Cells ◽

Uptake And Metabolism

The uptake and metabolism of chylomicron-remnant lipids by individual liver cell types was examined by incubating remnants with monolayer cultures of hepatocytes, Kupffer cells, and endothelial cells from rat liver. Remnants were prepared in vitro from radiolabelled mesenteric-lymph chylomicra, utilizing either purified lipoprotein lipase from bovine milk, or plasma isolated from heparinized rats. The resulting particles contained [3H]phosphatidylcholine and cholesterol, and [14C]oleate in the acylglycerol, phospholipid, fatty-acid and cholesterol-ester fractions. The capacities of the three cell types for uptake of both [3H]lipids and [14C]lipids were determined to be, on a per-cell basis, in the order: Kupffer greater than hepatocytes greater than endothelial. The relative proportions of [3H]phospholipid and total [3H]cholesterol taken up by hepatocytes and non-parenchymal cells remained constant with time. The uptake of [14C]oleoyl lipids by all three cell types was slightly greater than that of the total [3H]cholesterol and [3H]phospholipid components. There was evidence of cholesterol-ester hydrolysis and turnover of [14C]oleate in the phospholipid fraction in hepatocytes and Kupffer cells, but not endothelial cells, over the first 2 h. With both remnant preparations, these observations indicate that significant differences exist between the three major liver cell types with respect to the uptake and metabolism of remnant lipid components.

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Release of osmolytes induced by phagocytosis and hormones in rat liver

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.2000.278.2.g227 ◽

2000 ◽

Vol 278 (2) ◽

pp. G227-G233 ◽

Cited By ~ 11

Author(s):

Matthias Wettstein ◽

Thorsten Peters-Regehr ◽

Ralf Kubitz ◽

Richard Fischer ◽

Claudia Holneicher ◽

...

Keyword(s):

Endothelial Cells ◽

Cell Volume ◽

Rat Liver ◽

Kupffer Cells ◽

Hepatic Stellate Cells ◽

Stellate Cells ◽

Receptor Expression ◽

Sinusoidal Endothelial Cells ◽

Fluorescence Measurements ◽

Parenchymal Cells

Betaine, taurine, and inositol participate as osmolytes in liver cell volume homeostasis and interfere with cell function. In this study we investigated whether osmolytes are also released from the intact liver independent of osmolarity changes. In the perfused rat liver, phagocytosis of carbon particles led to a four- to fivefold stimulation of taurine efflux into the effluent perfusate above basal release rates. This taurine release was inhibited by 70–80% by the anion exchange inhibitor DIDS or by pretreatment of the rats with gadolinium chloride. Administration of vasopressin, cAMP, extracellular ATP, and glucagon also increased release of betaine and/or taurine, whereas insulin, extracellular UTP, and adenosine were without effect. In isolated liver cells, it was shown that parenchymal cells and sinusoidal endothelial cells, but not Kupffer cells and hepatic stellate cells, release osmolytes upon hormone stimulation. This may be caused by a lack of hormone receptor expression in these cells, because single-cell fluorescence measurements revealed an increase of intracellular calcium concentration in response to vasopressin and glucagon in parenchymal cells and sinusoidal endothelial cells but not in Kupffer cells and hepatic stellate cells. The data show that Kupffer cells release osmolytes during phagocytosis via DIDS-sensitive anion channels. This mechanism may be used to compensate for the increase in cell volume induced by the ingestion of phagocytosable material. The physiological significance of hormone-induced osmolyte release remains to be evaluated.

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Liver endothelium and not hepatocytes or Kupffer cells have transferrin receptors

Blood ◽

10.1182/blood.v63.2.270.bloodjournal632270 ◽

1984 ◽

Vol 63 (2) ◽

pp. 270-276

Author(s):

R Soda ◽

M Tavassoli

Keyword(s):

Endothelial Cells ◽

Rat Liver ◽

Kupffer Cells ◽

Liver Cell ◽

Cell Suspensions ◽

Transferrin Receptors ◽

Visual Probe ◽

Covalently Linked ◽

Parenchymal Cells

Using a visual probe, consisting of latex minibeads covalently linked to transferrin (TF), we found that, in rat liver cell suspensions, transferrin receptors were limited to endothelial cells. Neither hepatocytes nor Kupffer cells contained an appreciable number of TF receptors. Specificity of this reaction was demonstrated by preincubation with non-derivatized TF, which inhibited the binding. This was further confirmed by fractionation of liver cell suspensions on metrizamide gradients. The uptake of either the visual probe or 125I- labeled TF was again limited to the endothelium-rich fraction. Transferrin bound to endothelial membrane was internalized at 37 degrees C, but not at 4 degrees C, via a coated pit system. Again, hepatocytes and Kupffer cells did not internalize the probe. The findings suggest that iron may be first taken up by liver endothelium and then transmitted to parenchymal cells. These results emphasize the generally unappreciated role of endothelium in the transport across the tissue-blood barrier.

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Liver endothelium and not hepatocytes or Kupffer cells have transferrin receptors

Blood ◽

10.1182/blood.v63.2.270.270 ◽

1984 ◽

Vol 63 (2) ◽

pp. 270-276 ◽

Cited By ~ 54

Author(s):

R Soda ◽

M Tavassoli

Keyword(s):

Endothelial Cells ◽

Rat Liver ◽

Kupffer Cells ◽

Liver Cell ◽

Cell Suspensions ◽

Transferrin Receptors ◽

Visual Probe ◽

Covalently Linked ◽

Parenchymal Cells

Abstract Using a visual probe, consisting of latex minibeads covalently linked to transferrin (TF), we found that, in rat liver cell suspensions, transferrin receptors were limited to endothelial cells. Neither hepatocytes nor Kupffer cells contained an appreciable number of TF receptors. Specificity of this reaction was demonstrated by preincubation with non-derivatized TF, which inhibited the binding. This was further confirmed by fractionation of liver cell suspensions on metrizamide gradients. The uptake of either the visual probe or 125I- labeled TF was again limited to the endothelium-rich fraction. Transferrin bound to endothelial membrane was internalized at 37 degrees C, but not at 4 degrees C, via a coated pit system. Again, hepatocytes and Kupffer cells did not internalize the probe. The findings suggest that iron may be first taken up by liver endothelium and then transmitted to parenchymal cells. These results emphasize the generally unappreciated role of endothelium in the transport across the tissue-blood barrier.

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Cadmium metabolism by rat liver endothelial and Kupffer cells

Biochemical Journal ◽

10.1042/bj2210631 ◽

1984 ◽

Vol 221 (3) ◽

pp. 631-636 ◽

Cited By ~ 15

Author(s):

T J Caperna ◽

M L Failla

Keyword(s):

Endothelial Cells ◽

Rat Liver ◽

Kupffer Cells ◽

Metal Binding ◽

Metal Salt ◽

Extracellular Medium ◽

Competitive Binding Assay ◽

Monolayer Cultures ◽

Parenchymal Cells

The metabolism of cadmium was investigated in Wistar-rat liver non-parenchymal cells. Kupffer and endothelial cells, the major cell populations lining the sinusoidal tracts, were isolated by collagenase dispersion and purified by centrifugal elutriation. At 20 h after subcutaneous injection of the metal salt (1.5 mg of Cd/kg body weight), endothelial cells accumulated 2-fold higher concentrations of Cd than did Kupffer or parenchymal cells. Most of the Cd in non-parenchymal cells was associated with cytosolic metallothionein (MT), the low-Mr heavy-metal-binding protein(s). When MT was quantified in cytosols from cells isolated from control rats by a 203Hg competitive-binding assay, low levels were found to be present in Kupffer, endothelial and parenchymal cells. Cd injection significantly increased MT levels in all three cell types. The induction of MT synthesis was investigated in vitro by using primary monolayer cultures. The incorporation of [35S]cysteine into MT increased 47% over constitutive levels in endothelial-cell cultures after the addition of 0.8 microM-Cd2+ to the medium for 10 h. MT synthesis in Kupffer cells was not observed. The lack of MT synthesis by monolayer cultures of Kupffer cells in vitro was associated with a decreased capacity of these cells to accumulate heavy metals from the extracellular medium. This apparent decreased ability to transport metals did not reflect a general defect in either cellular function or metabolic activity, since isolated Kupffer cells incorporated [3H]leucine into protein at rates comparable with those shown by liver parenchymal cells and readily phagocytosed particles.

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Transport of tyramine in short-term cultured rat liver parenchymal cells, endothelial cells and Kupffer cells

International Hepatology Communications ◽

10.1016/0928-4346(94)00161-w ◽

1995 ◽

Vol 3 (2) ◽

pp. 105-111

Author(s):

Z ZHONG ◽

M PIROTTEWARNIER ◽

A VUYLSTEKE ◽

S CONINCK ◽

R WATTIAUX

Keyword(s):

Endothelial Cells ◽

Rat Liver ◽

Kupffer Cells ◽

Short Term ◽

Liver Parenchymal ◽

Parenchymal Cells

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Role of the scavenger receptor in the uptake of methylamine-activated α2-macroglobulin by rat liver

Biochemical Journal ◽

10.1042/bj2870447 ◽

1992 ◽

Vol 287 (2) ◽

pp. 447-455 ◽

Cited By ~ 12

Author(s):

M C M van Dijk ◽

W Boers ◽

C Linthorst ◽

T J C van Berkel

Keyword(s):

Endothelial Cells ◽

Rat Liver ◽

Kupffer Cells ◽

Proteolytic Enzymes ◽

Scavenger Receptor ◽

Liver Cells ◽

Cell Protein ◽

Liver Uptake ◽

Inosinic Acid ◽

Parenchymal Cells

Alpha 2-Macroglobulin (alpha 2M) requires activation by small nucleophiles (e.g. methylamine; giving alpha 2M-Me) or proteolytic enzymes (e.g. trypsin; giving alpha 2M-Tr) in order to be rapidly removed from the circulation by the liver. Separation of rat liver cells into parenchymal, endothelial and Kupffer cells at 10 min after injection indicates that liver uptake of alpha 2M-Me is shared between parenchymal and endothelial cells, with relative contributions of 51.3% and 48.3% respectively of total liver-associated radioactivity. In contrast, alpha 2M-Tr is almost exclusively taken up by the parenchymal cells (90.1% of liver-associated radioactivity). A preinjection of 5 mg of poly(inosinic acid) decreased liver uptake of alpha 2M-Me to 39.9% of the control value, while it had no effect on liver uptake of alpha 2M-Tr. It appears that poly(inosinic acid) specifically reduces the uptake of alpha 2M-Me in vivo by endothelial cells, leaving uptake by parenchymal cells unaffected. In vitro studies with isolated liver cells indicate that the association of alpha 2M-Me with endothelial cells is 21-fold higher per mg of cell protein than with parenchymal cells. The capacity of endothelial cells to degrade alpha 2M-Me appears to be 46 times higher than that of parenchymal cells. Competition studies show that poly(inosinic acid) or acetylated low-density lipoprotein effectively competes with the association of alpha 2M-Me with endothelial and Kupffer cells, but association with parenchymal cells is unaffected. It is suggested that activation of alpha 2M by methylamine induces a charge distribution on the protein which triggers specific uptake by the scavenger receptor on endothelial cells. It is concluded that the uptake of alpha 2M-Me by the scavenger receptor might function as an additional system for the uptake of activated alpha 2M.

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The distribution, induction and isoenzyme profile of glutathione S-transferase and glutathione peroxidase in isolated rat liver parenchymal, Kupffer and endothelial cells

Biochemical Journal ◽

10.1042/bj2640737 ◽

1989 ◽

Vol 264 (3) ◽

pp. 737-744 ◽

Cited By ~ 18

Author(s):

P Steinberg ◽

H Schramm ◽

L Schladt ◽

L W Robertson ◽

H Thomas ◽

...

Keyword(s):

Endothelial Cells ◽

Glutathione Peroxidase ◽

Rat Liver ◽

Peroxidase Activity ◽

Cell Types ◽

Transferase Activity ◽

Glutathione Peroxidase Activity ◽

Glutathione S Transferase ◽

Liver Parenchymal ◽

Parenchymal Cells

The distribution and inducibility of cytosolic glutathione S-transferase (EC 2.5.1.18) and glutathione peroxidase (EC 1.11.1.19) activities in rat liver parenchymal, Kupffer and endothelial cells were studied. In untreated rats glutathione S-transferase activity with 1-chloro-2,4-dinitrobenzene and 4-hydroxynon-2-trans-enal as substrates was 1.7-2.2-fold higher in parenchymal cells than in Kupffer and endothelial cells, whereas total, selenium-dependent and non-selenium-dependent glutathione peroxidase activities were similar in all three cell types. Glutathione S-transferase isoenzymes in parenchymal and non-parenchymal cells isolated from untreated rats were separated by chromatofocusing in an f.p.l.c. system: all glutathione S-transferase isoenzymes observed in the sinusoidal lining cells were also detected in the parenchymal cells, whereas Kupffer and endothelial cells lacked several glutathione S-transferase isoenzymes present in parenchymal cells. At 5 days after administration of Arocolor 1254 glutathione S-transferase activity was only enhanced in parenchymal cells; furthermore, selenium-dependent glutathione peroxidase activity decreased in parenchymal and non-parenchymal cells. At 13 days after a single injection of Aroclor 1254 a strong induction of glutathione S-transferase had taken place in all three cell types, whereas selenium-dependent glutathione peroxidase activity remained unchanged (endothelial cells) or was depressed (parenchymal and Kupffer cells). Hence these results clearly establish that glutathione S-transferase and glutathione peroxidase are differentially regulated in rat liver parenchymal as well as non-parenchymal cells. The presence of glutathione peroxidase and several glutathione S-transferase isoenzymes capable of detoxifying a variety of compounds in Kupffer and endothelial cells might be crucial to protect the liver from damage by potentially hepatotoxic substances.

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