Restructuring of plasma membrane phospholipids in isolated hepatocytes of rainbow trout during brief in vitro cold exposure

1995 ◽  
Vol 164 (8) ◽  
pp. 600-608 ◽  
Author(s):  
E. E. Williams ◽  
J. R. Hazel
Keyword(s):  
Plasma Membrane ◽  
Rainbow Trout ◽  
Cold Exposure ◽  
Isolated Hepatocytes ◽  
Membrane Phospholipids

Regulation of glucose production in rainbow trout: role of epinephrine in vivo and in isolated hepatocytes

2000 ◽  
Vol 278 (4) ◽  
pp. R956-R963 ◽  
Author(s):  
Jean-Michel Weber ◽  
Deena S. Shanghavi
Keyword(s):  
Rainbow Trout ◽  
Hepatic Glucose Production ◽  
Glucose Production ◽  
Isolated Hepatocytes ◽  
Relative Increase ◽  
Dependent Manner ◽  
Rainbow Trout Oncorhynchus Mykiss

The rate of hepatic glucose production (Ra glucose) of rainbow trout ( Oncorhynchus mykiss) was measured in vivo by continuous infusion of [6-3H]glucose and in vitro on isolated hepatocytes to examine the role of epinephrine (Epi) in its regulation. By elevating Epi concentration and/or blocking β-adrenoreceptors with propranolol (Prop), our goals were to investigate the mechanism for Epi-induced hyperglycemia to determine the possible role played by basal Epi concentration in maintaining resting Ra glucose and to assess indirect effects of Epi in the intact animal. In vivo infusion of Epi caused hyperglycemia (3.75 ± 0.16 to 8.75 ± 0.54 mM) and a twofold increase in Ra glucose (6.57 ± 0.79 to 13.30 ± 1.78 μmol ⋅ kg− 1 ⋅ min− 1, n = 7), whereas Prop infusion decreased Ra from 7.65 ± 0.92 to 4.10 ± 0.56 μmol ⋅ kg− 1 ⋅ min− 1( n = 10). Isolated hepatocytes increased glucose production when treated with Epi, and this response was abolished in the presence of Prop. We conclude that Epi-induced trout hyperglycemia is entirely caused by an increase in Ra glucose, because the decrease in the rate of glucose disappearance normally seen in mammals does not occur in trout. Basal circulating levels of Epi are involved in maintaining resting Ra glucose. Epi stimulates in vitro glucose production in a dose-dependent manner, and its effects are mainly mediated by β-adrenoreceptors. Isolated trout hepatocytes produce glucose at one-half the basal rate measured in vivo, even when diet, temperature, and body size are standardized, and basal circulating Epi is responsible for part of this discrepancy. The relative increase in Ra glucose after Epi stimulation is similar in vivo and in vitro, suggesting that indirect in vivo effects of Epi, such as changes in hepatic blood flow or in other circulating hormones, do not play an important role in the regulation of glucose production in trout.

Effect of glucagon on hepatic taurocholate uptake: relationship to membrane potential

1985 ◽  
Vol 249 (4) ◽  
pp. G427-G433
Author(s):  
J. W. Edmondson ◽  
B. A. Miller ◽  
L. Lumeng
Keyword(s):  
Plasma Membrane ◽  
Bile Acid ◽  
Membrane Potential ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Hill Coefficient ◽  
Isolated Rat Hepatocytes ◽  
Plasma Membrane Potential ◽  
Sodium Dependent

Since glucagon can hyperpolarize hepatic plasma membrane and stimulate biliary bile acid secretion in vitro, we studied the effect of glucagon on taurocholate uptake and its relationship to plasma membrane potential in isolated rat hepatocytes. [14C]taurocholate uptake was linear through 1 min and contained a saturable sodium-dependent and a nonsaturable sodium-independent component. Km of taurocholate uptake by the sodium-dependent system was 18.4 microM. Hill coefficient for Na+ was 2.59 and for taurocholate was 1.1, suggesting that the stoichiometry is 2 Na+:1 bile acid. Stimulation of taurocholate uptake by glucagon was limited to the sodium-dependent component, detected within 5 min of hormone exposure, and was maximum at 30 min. Glucagon, from 10(-8) to 10(-5) M, stimulated taurocholate uptake and hyperpolarized concurrently the plasma membrane potential. Because valinomycin produced a dose-related depolarization of plasma membrane potential, this agent was used to counteract the effects of glucagon. With 10(-6) M glucagon, valinomycin (10(-10) M) depolarized membrane potential from -35.50 to -28.00 mV and inhibited taurocholate uptake from 60% above the control rate to 5% below. These data strongly suggest that taurocholate uptake by isolated hepatocytes is an electrogenic process, and its stimulation by glucagon may be mediated by changes in plasma membrane potential.

scholarly journals Delayed restoration of Mg2+ content and transport in liver cells following ethanol withdrawal

2009 ◽  
Vol 297 (4) ◽  
pp. G621-G631 ◽  
Author(s):  
Lisa M. Torres ◽  
Christie Cefaratti ◽  
Liliana Berti-Mattera ◽  
Andrea Romani
Keyword(s):  
Plasma Membrane ◽  
Membrane Vesicles ◽  
Isolated Hepatocytes ◽  
Liver Cells ◽  
Ethanol Withdrawal ◽  
Adrenergic Stimulation ◽  
Plasma Membrane Vesicles ◽  
Isolated Cells ◽  
Intact Cells

Liver cells from rats chronically fed a Lieber-De Carli diet for 3 wk presented a marked decreased in tissue Mg2+ content and an inability to extrude Mg2+ into the extracellular compartment upon stimulation with catecholamine, isoproterenol, or cell-permeant cAMP analogs. This defect in Mg2+ extrusion was observed in both intact cells and purified liver plasma membrane vesicles. Inhibition of adrenergic or cAMP-mediated Mg2+ extrusion was also observed in freshly isolated hepatocytes from control rats incubated acutely in vitro with varying doses of ethanol (EtOH) for 8 min. In this model, however, the defect in Mg2+ extrusion was observed in intact cells but not in plasma membrane vesicles. In the chronic model, upon removal of EtOH from the diet hepatic Mg2+ content and extrusion required ∼10 days to return to normal level both in isolated cells and plasma membrane vesicles. In hepatocytes acutely treated with EtOH for 8 min, more than 60 min were necessary for Mg2+ content and extrusion to recover and return to the level observed in EtOH-untreated cells. Taken together, these data suggest that in the acute model the defect in Mg2+ extrusion is the result of a limited refilling of the cellular compartment(s) from which Mg2+ is mobilized upon adrenergic stimulation rather than a mere defect in adrenergic cellular signaling. The chronic EtOH model, instead, presents a transient but selective defect of the Mg2+ extrusion mechanisms in addition to the limited refilling of the cellular compartments.

scholarly journals Methyl group transfer from exogenous S-adenosylmethionine on to plasma-membrane phospholipids without cellular uptake in isolated hepatocytes

1982 ◽  
Vol 206 (3) ◽  
pp. 481-487 ◽  
Author(s):  
L Van Phi ◽  
H D Söling
Keyword(s):  
Plasma Membrane ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Methyl Groups ◽  
Membrane Phospholipids ◽  
Small Pool ◽  
Cellular Compartments ◽  
Phospholipid Species ◽  
Water Space ◽  
Methyl Group Transfer

At external concentration of 50 microM, L-methionine was rapidly taken up by hepatocytes, whereas almost no S-adenosylmethionine (SAM) was removed from the incubation medium. SAM did not enter the intracellular water space but equilibrated with a very small pool, which was most likely to be situated on the external side of the plasma membrane. Methyl groups from external L-methionine, but not from external SAM, were incorporated into total and nuclear RNA. A significant incorporation of methyl groups into phospholipids occurred not only with methionine but also with SAM. After subfractionation of hepatocytes it became evident that methyl groups from SAM were mainly incorporated into plasma-membrane phospholipids, and that phospholipid methylation in other cellular compartments resulted from contamination with plasma membrane. The pattern of methylation of the various phospholipid species with SAM as precursor was different from that obtained with L-methionine. In contrast with external L-methionine, external SAM did not enter the intracellular SAM pool. According to these results a transport system for SAM does not exist in rat hepatocytes, although methyl groups from external SAM can be incorporated into plasma-membrane phospholipids from the outside.

Membrane fluidity and hemilayer temperature sensitivity in trout hepatocytes during brief in vitro cold exposure

1994 ◽  
Vol 266 (3) ◽  
pp. R773-R780
Author(s):  
E. E. Williams ◽  
J. R. Hazel
Keyword(s):  
Plasma Membrane ◽  
Cold Exposure ◽  
Plasma Membranes ◽  
Temperature Acclimation ◽  
Short Term ◽  
Fluorescence Depolarization ◽  
Intact Cells ◽  
Induced Membrane ◽  
Membrane Probes

Fluorescent membrane probes were used to assess the fluidity of hepatocyte plasma membranes (PM) from 20 degrees C-acclimated trout after exposure to 20 and 5 degrees C. PM isolated from cells after 6 h at 5 degrees C were significantly more fluid [fluorescence depolarization of 1,6-diphenyl-1,3,5-hexatriene (DPH)] than control membranes at both temperatures. The increased fluidity was sufficient to offset 45-50% of the cold-induced membrane ordering. In contrast, the fluidity of PM in intact cells from 20 degrees C-acclimated fish remained constant when exposed to 5 degrees C for a similar period. In addition, the fluidity of the inner hemilayer [1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene, p-toluenesulfonate (TMA-DPH)] was significantly less sensitive to temperature change than was the fluidity of the outer hemilayer [3-(p-(6-phenyl)-1,3,5-hexatrienyl)phenylpropionic acid (PA-DPH)]. Because the isolated membrane preparation was most likely enriched with canalicular membranes (based on 5'-nucleotidase recovery), these results suggest that the canalicular domain of the plasma membrane is preferentially modified during short-term cold exposure and that the fluidity of the inner hemilayer of the plasma membrane of intact cells is relatively temperature insensitive, thus requiring fewer modifications than the outer hemilayer during temperature acclimation.

scholarly journals RNF141 interacts with KRAS to promote colorectal cancer progression

Oncogene ◽  
2021 ◽  
Author(s):  
Jiuna Zhang ◽  
Xiaoyu Jiang ◽  
Jie Yin ◽  
Shiying Dou ◽  
Xiaoli Xie ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Plasma Membrane ◽  
Tumor Growth ◽  
Cancer Progression ◽  
Critical Role ◽  
Ring Finger ◽  
Immunohistochemical Analysis ◽  
Bimolecular Fluorescence Complementation

AbstractRING finger proteins (RNFs) play a critical role in cancer initiation and progression. RNF141 is a member of RNFs family; however, its clinical significance, roles, and mechanism in colorectal cancer (CRC) remain poorly understood. Here, we examined the expression of RNF141 in 64 pairs of CRC and adjacent normal tissues by real-time PCR, Western blot, and immunohistochemical analysis. We found that there was more expression of RNF141 in CRC tissue compared with its adjacent normal tissue and high RNF141 expression associated with T stage. In vivo and in vitro functional experiments were conducted and revealed the oncogenic role of RNF141 in CRC. RNF141 knockdown suppressed proliferation, arrested the cell cycle in the G1 phase, inhibited migration, invasion and HUVEC tube formation but promoted apoptosis, whereas RNF141 overexpression exerted the opposite effects in CRC cells. The subcutaneous xenograft models showed that RNF141 knockdown reduced tumor growth, but its overexpression promoted tumor growth. Mechanistically, liquid chromatography-tandem mass spectrometry indicated RNF141 interacted with KRAS, which was confirmed by Co-immunoprecipitation, Immunofluorescence assay. Further analysis with bimolecular fluorescence complementation (BiFC) and Glutathione-S-transferase (GST) pull-down assays showed that RNF141 could directly bind to KRAS. Importantly, the upregulation of RNF141 increased GTP-bound KRAS, but its knockdown resulted in a reduction accordingly. Next, we demonstrated that RNF141 induced KRAS activation via increasing its enrichment on the plasma membrane not altering total KRAS expression, which was facilitated by the interaction with LYPLA1. Moreover, KRAS silencing partially abolished the effect of RNF141 on cell proliferation and apoptosis. In addition, our findings presented that RNF141 functioned as an oncogene by upregulating KRAS activity in a manner of promoting KRAS enrichment on the plasma membrane in CRC.

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