Release of osmolytes induced by phagocytosis and hormones in rat liver

2000 ◽  
Vol 278 (2) ◽  
pp. G227-G233 ◽  
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.

scholarly journals Endothelin-1 in portal hypertension: The intricate role of hepatic stellate cells

2020 ◽  
Vol 245 (16) ◽  
pp. 1504-1512 ◽  
Author(s):  
Devaraj Ezhilarasan
Keyword(s):  
Extracellular Matrix ◽  
Endothelial Cells ◽  
Portal Hypertension ◽  
Hepatic Stellate Cells ◽  
Stellate Cells ◽  
Chronic Liver ◽  
Liver Sinusoidal Endothelial Cells ◽  
Sinusoidal Endothelial Cells ◽  
Endothelin 1 ◽  
Activated Hepatic Stellate Cells

Portal hypertension is one of the most important cirrhosis-associated complications of chronic liver disease, leading to significant morbidity and mortality. After chronic liver injury, hepatic stellate cells reside in the perisinusoidal space activted and acquire a myofibroblast-like phenotype. The activated hepatic stellate cells act as both sources as well as the target for a potent vasoconstrictor endothelin-1. Activation of hepatic stellate cells plays a vital role in the onset of cirrhosis by way of increased extracellular matrix production and the enhanced contractile response to vasoactive mediators such as endothelin-1. In fibrotic/cirrhotic liver, activated hepatic stellate cells produce endothelin-1 leading to an imbalance between pro and antifibrotic factors responsible for enormous extracellular matrix synthesis. Thus, extracellular matrix deposition in the perisinusoidal space further augments liver stiffness and elevates the vascular tone and portal hypertension. Portal hypertension is a complex process modulated by several cell types like hepatic stellate cells, liver sinusoidal endothelial cells, Kupffer cells, injured hepatocytes, immune cells, and biliary epithelial cells. Therefore, targeting a single cell type may not be useful for regression of cirrhosis and portal hypertension. Nevertheless, numerous findings indicate that functionally liver sinusoidal endothelial cells and hepatic stellate cells closely regulate the sinusoidal blood flow via synthesis of several vasoactive molecules including endothelin-1, and hence targeting these cells with novel pharmacological agents may offer promising results. Impact statement Portal hypertension is pathologically defined as increase of portal venous pressure, mainly due to chronic liver diseases such as fibrosis and cirrhosis. In fibrotic liver, activated hepatic stellate cells increase their contraction in response to endothelin-1 (ET-1) via autocrine and paracrine stimulation from liver sinusoidal endothelial cells and injured hepatocytes. Clinical studies are limited with ET receptor antagonists in cirrhotic patients with portal hypertension. Hence, studies are needed to find molecules that block ET-1 synthesis. Accumulation of extracellular matrix proteins in the perisinusoidal space, tissue contraction, and alteration in blood flow are prominent during portal hypertension. Therefore, novel matrix modulators should be tested experimentally as well as in clinical studies. Specifically, tumor necrosis factor-α, transforming growth factor-β1, Wnt, Notch, rho-associated protein kinase 1 signaling antagonists, and peroxisome proliferator-activated receptor α and γ, interferon-γ and sirtuin 1 agonists should be tested elaborately against cirrhosis patients with portal hypertension.

scholarly journals Hepatic lipase is localized at the parenchymal cell microvilli in rat liver

1997 ◽  
Vol 321 (2) ◽  
pp. 425-430 ◽  
Author(s):  
Belinda BREEDVELD ◽  
Kees SCHOONDERWOERD ◽  
Adrie J. M. VERHOEVEN ◽  
Rob WILLEMSEN ◽  
Hans JANSEN
Keyword(s):  
Endothelial Cells ◽  
Rat Liver ◽  
Kupffer Cells ◽  
Binding Capacity ◽  
Hepatic Lipase ◽  
Parenchymal Cell ◽  
Liver Cells ◽  
Minor Amount ◽  
Parenchymal Liver ◽  
Parenchymal Cells

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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