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.

Regulation of plasma membrane permeability to calcium in primary cultures of rat hepatocytes

Cell Calcium ◽  
1991 ◽  
Vol 12 (8) ◽  
pp. 559-575 ◽  
Author(s):  
Y Zhang ◽  
J Duszynski ◽  
S Hreniuk ◽  
M.M Waybill ◽  
K.F LaNoue
Keyword(s):  
Plasma Membrane ◽  
Membrane Permeability ◽  
Primary Cultures ◽  
Rat Hepatocytes ◽  
Plasma Membrane Permeability

scholarly journals Sugar uptake by fluid-phase pinocytosis and diffusion in isolated rat hepatocytes

1987 ◽  
Vol 243 (3) ◽  
pp. 655-660 ◽  
Author(s):  
P B Gordon ◽  
H Høyvik ◽  
P O Seglen
Keyword(s):  
Plasma Membrane ◽  
Fluid Phase ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Free Sugar ◽  
Sugar Uptake ◽  
Isolated Rat Hepatocytes ◽  
Fluid Phase Endocytosis ◽  
And Diffusion ◽  
Isolated Rat

Measurements of sugar pinocytosis (fluid-phase endocytosis of radiolabelled sucrose, lactose and raffinose) in freshly isolated rat hepatocytes are disturbed by sugar diffusing into the cells through plasma-membrane blebs. Non-pinocytic entry may be even more pronounced at 0 degrees C, and is a major contributor to ‘background’ radioactivity. By electrodisruption of the plasma membrane, a distinction can be made between pinocytotically sequestered sugar and free sugar that has entered the cytosol by diffusion. Pinocytosis proceeds at a rate of 2%/h (relative to the intracellular fluid volume), whereas the rate of sucrose entry by diffusion is more than twice as high. Three pinocytotic compartments are distinguishable in isolated hepatocytes: (1) a rapidly recycling compartment, which is completely destroyed by electrodisruption, and which may represent pinocytic channels continuous with the plasma membrane; (2) a non-recycling (or very slowly recycling) electrodisruption-resistant compartment, which allows accumulation of the lysosomally hydrolysable sugar lactose, and which therefore must represent non-lysosomal vacuoles (endosomes?); (3) a lysosomal compartment (non-recycling, electrodisruption-resistant), which accumulates raffinose and sucrose, but which hydrolyses lactose. The last two compartments can be partially resolved in metrizamide/sucrose density gradients by the use of different sugar probes.

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

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 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.

Hormonal induction of malic enzyme in rat hepatocytes cultured on laminin-rich gels

1992 ◽  
Vol 8 (3) ◽  
pp. 235-242 ◽  
Author(s):  
D. J. Mann ◽  
A. J. Strain ◽  
E. Bailey
Keyword(s):  
Malic Enzyme ◽  
Primary Cultures ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Specific Expression ◽  
Adult Rat ◽  
Adult Rat Hepatocytes ◽  
Species Being ◽  
Rat Tail

ABSTRACT The levels of malic-enzyme mRNA and activity were determined in primary cultures of adult rat hepatocytes maintained on either rat-tail collagen or a laminin-rich substratum. Cells plated on laminin-rich gels exhibited substantially improved patterns of albumin and malic-enzyme expression when compared with cells maintained on rat-tail collagen. Moreover, hepatocytes plated on the laminin-rich matrix displayed marked malic-enzyme inducibility in response to tri-iodothyronine and dichloroacetate, especially in the presence of insulin. However, Northern blot analysis revealed that the ratio of the amounts of the two major malic-enzyme mRNA species (2.0 and 3.1 kb) was reversed when compared with that found in the liver in vivo, the altered levels of these two species being closer to those found in non-hepatic tissues. These findings indicate that, although the hormonal responsiveness of isolated hepatocytes maintained on laminin-rich gels is markedly improved, and approaches the degree of induction demonstrated in the liver in vivo, the mechanisms of control differ, indicating a loss of liver-specific expression.

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 Selective release of plasma-membrane enzymes from rat hepatocytes by a phosphatidylinositol-specific phospholipase C

1980 ◽  
Vol 187 (1) ◽  
pp. 277-280 ◽  
Author(s):  
S D Shukla ◽  
R Coleman ◽  
J B Finean ◽  
R H Michell
Keyword(s):  
Alkaline Phosphatase ◽  
Plasma Membrane ◽  
Cell Surface ◽  
Phospholipase C ◽  
Inositol Phosphate ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Membrane Enzymes

When isolated hepatocytes are incubated with phosphatidylinositol-specific phospholipase C, three cell-surface enzymes show markedly different behaviour. Most of the alkaline phosphatase is released at very low values of phosphatidylinositol hydrolysis, whereas further phosphatidylinositol hydrolysis releases only a maximum of about one-third of the 5′-nucleotidase. Alkaline phosphodiesterase I is not released. If cells containing phosphatidyl[3H]inositol are similarly treated, then the released [3H]inositol is in the form of inositol phosphate: no evidence has been obtained for any covalent association between released [3H]inositol and alkaline phosphatase.

Sign in / Sign up

Export Citation Format

Share Document