Hormonal Modulation of Hepatic Plasma Membrane Lactate Transport in Cultured Rat Hepatocytes

1990 ◽  
Vol 79 (s23) ◽  
pp. 17P-17P
Author(s):  
HK Metcalfe ◽  
RD Cohen ◽  
JP Monson
Keyword(s):  
Plasma Membrane ◽  
Rat Hepatocytes ◽  
Lactate Transport ◽  
Hormonal Modulation ◽  
Cultured Rat Hepatocytes

Hormonal modulation of hepatic plasma membrane lactate transport in cultured rat hepatocytes

1990 ◽  
Vol 10 (6) ◽  
pp. 573-577 ◽  
Author(s):  
H. K. Metcalfe ◽  
R. D. Cohen ◽  
J. P. Monson
Keyword(s):  
Plasma Membrane ◽  
Primary Cultures ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Similar Magnitude ◽  
Potential Mechanism ◽  
Lactate Transport ◽  
Hormonal Modulation ◽  
Cultured Rat Hepatocytes

Hormonal modulation of hepatic plasma membrane lactate transport was studied in primary cultures of isolated hepatocytes from fed rats to examine the mechanism for the known enhancement of lactate transport in starvation and diabetes. Total cellular lactate entry was increased by 14% in the presence of dexamethasone; this was accounted for by an approximately 40% increase in the carrier-mediated component of entry with no effect on diffusion. A trend of similar magnitude was evident with glucagon. The effects of dexamethasone and glucagon on lactate transport constitute an additional potential mechanism for enhancement of gluconeogenesis by these hormones.

Inhibitory effect of colchicine and vinblastine on transport of glucagon receptors to the plasma membrane in cultured rat hepatocytes

1985 ◽  
Vol 106 (1) ◽  
pp. 125-131 ◽  
Author(s):  
J. Watanabe ◽  
S. Kanamura ◽  
K. Kanai ◽  
M. Asada-Kubota ◽  
M. Oka
Keyword(s):  
Plasma Membrane ◽  
Rat Hepatocytes ◽  
Inhibitory Effect ◽  
Scatchard Analysis ◽  
Glucagon Receptor ◽  
Cultured Rat Hepatocytes ◽  
Glucagon Receptors

ABSTRACT The role of microtubules in the regulation of glucagon receptors on cultured rat hepatocytes was studied. Antimicrotubular reagents, colchicine and vinblastine, did not affect the binding of 125I-labelled glucagon to hepatocytes at 4°C. At 20 and 37 °C, however, the reagents reduced the binding after 60 or 90 min of incubation. Scatchard analysis indicated that the reduction in the binding was due to loss of glucagon-receptor populations. If hepatocytes were preincubated with both unlabelled glucagon and the reagents at 37 °C, the binding of the ligand to the cells decreased markedly after a certain delay. The reagents did not inhibit the internalization of the ligand in the cells until 30 min of incubation at 37 °C. The results suggest that the microtubule system plays a role in the transport of glucagon receptors to the plasma membrane, which is followed by their internalization. J. Endocr. (1985) 106, 125–131

Cytochrome P4502B follows a vesicular route to the plasma membrane in cultured rat hepatocytes

1995 ◽  
Vol 108 (4) ◽  
pp. 1110-1123 ◽  
Author(s):  
Marie-Anne Robin ◽  
Michel Maratrat ◽  
Jacqueline Loeper ◽  
Anne-Marie Durand-Schneider ◽  
Marina Tinel ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Rat Hepatocytes ◽  
Cultured Rat Hepatocytes

scholarly journals Cleavage of membrane secretory component to soluble secretory component occurs on the cell surface of rat hepatocyte monolayers.

1987 ◽  
Vol 104 (6) ◽  
pp. 1725-1733 ◽  
Author(s):  
L S Musil ◽  
J U Baenziger
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Rat Hepatocytes ◽  
Integral Membrane Protein ◽  
Secretory Component ◽  
Soluble Form ◽  
Membrane Domain ◽  
Transcellular Transport ◽  
Cultured Rat Hepatocytes ◽  
Plasma Membrane Domain

Rat liver secretory component is synthesized as an integral membrane protein (mSC) and cleaved to an 80-kD soluble form (fSC) sometime during transcellular transport from the sinusoidal to the bile canalicular plasma membrane domain of hepatocytes. We have used 24-h monolayer cultures of rat hepatocytes to characterize the conversion of mSC to fSC. Cleavage of mSC in cultured hepatocytes is inhibited by the thiol protease inhibitors leupeptin, antipain, and E-64, but not by other inhibitors, including disopropylfluorophosphate, pepstatin, N-ethylmalemide, p-chloromercuribenzoic acid, and chloroquine. Leupeptin-mediated inhibition of cleavage is concentration dependent and reversible. In the presence or absence of leupeptin, only 10-20% of mSC is accessible at the cell surface. To characterize the behavior of surface as opposed to intracellular mSC, cell surface mSC was labeled with 125I by lactoperoxidase-catalyzed iodination at 4 degrees C. Cell surface 125I-mSC was converted to extracellular fSC at 4 degrees C in the absence of detectable internalization. Cleavage was inhibited by leupeptin and by anti-secretory component antiserum. Cleavage also occurred at 4 degrees C after cell disruption. In contrast, 125I-mSC that had been internalized from the cell surface was not converted to fSC at 4 degrees C in either intact or disrupted cells. Hepatocytes metabolically labeled with [35S]cys also released small quantities of fSC into the medium at 4 degrees C. The properties of fSC production indicate that cleavage occurs on the surface of cultured rat hepatocytes and not intracellularly. Other features of the cleavage reaction suggest that the mSC-cleaving protease is segregated from the majority of cell surface mSC, possibly within a specialized plasma membrane domain.

scholarly journals Ligand-dependent redistribution of the IgA receptor on cultured rat hepatocytes and its disturbance by cytochalasin B.

1987 ◽  
Vol 35 (3) ◽  
pp. 301-309 ◽  
Author(s):  
R Gebhardt ◽  
H Robenek
Keyword(s):  
Plasma Membrane ◽  
Colloidal Gold ◽  
Cytochalasin B ◽  
Rat Hepatocytes ◽  
Secretory Component ◽  
Coated Vesicles ◽  
Cell Periphery ◽  
Cultured Hepatocytes ◽  
Coated Pits ◽  
Cultured Rat Hepatocytes

The topography and dynamics of IgA-secretory component (SC) complexes on the surface of cultured hepatocytes and its disturbance by cytochalasin B were investigated using the colloidal gold technique in conjunction with surface replication. The distribution of IgA-gold conjugates after incubation at 4 degrees C was similar in normal and cytochalasin B-treated hepatocytes and was characterized by diffusely scattered single and clustered particles, the latter often associated with coated pits. After raising the temperature to 37 degrees C, redistribution of particles and their gradual uptake into coated vesicles was observed in control cultures. This ligand-induced redistribution led to a progressive gathering of single and grouped particles in larger clusters (50-200 particles), which appeared to be the site of the most intensive endocytotic activity. In contrast, huge patches of IgA-gold conjugates were formed at the cell periphery of cytochalasin B-treated hepatocytes within 20-60 min at 37 degrees C, while central areas were cleared. Patch formation was triggered by binding of both unlabeled and labeled IgA, but could not be observed with the unoccupied receptor as demonstrated by gold-labeled antibodies against SC. These results show that the topography of SC is markedly changed by binding of its ligand, IgA, and suggest that the dynamics of the IgA-SC complexes in hepatocyte plasma membrane are affected by microfilaments.

Role of hepatocyte plasma membrane in insulin degradation

1985 ◽  
Vol 248 (2) ◽  
pp. E194-E202
Author(s):  
W. G. Blackard ◽  
C. Ludeman ◽  
J. Stillman
Keyword(s):  
Plasma Membrane ◽  
Cell Membrane ◽  
Trichloroacetic Acid ◽  
Rat Hepatocytes ◽  
Inhibitory Effect ◽  
Insulin Degradation ◽  
Compensatory Increase ◽  
Cultured Rat Hepatocytes ◽  
Surface Active

An important role of the cell membrane in insulin degradation by cultured rat hepatocytes is supported by studies using the surface-active antibiotic bacitracin. Bacitracin inhibited degradation of cell-associated insulin (both randomly and A14 labeled) by 80–90% at 15 degrees C and by 60% at 37 degrees C. At 37 degrees C, inhibition of degradation was observed only with bacitracin present during dissociation and was accompanied by a compensatory increase in release of trichloroacetic acid (TCA)-precipitable insulin. This profile suggests inhibition of insulin degradation on the membrane after either primary binding or diacytosis (endocytosis-reverse endocytosis). In contrast, at 15 degrees C, bacitracin's inhibitory effect was greater with the antibiotic present during association and was not accompanied by a compensatory increase in TCA-precipitable insulin. This profile was compatible with inhibition of partial cleavage of insulin on the membrane. Internalization and degradation through chloroquine-sensitive pathways may be required to complete degradation at this temperature because chloroquine exhibited an inhibitory effect on insulin degradation equally potent to that of bacitracin at 15 degrees C (no effect at 37 degrees C).

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