scholarly journals Solubilization and reconstitution of a nucleoside-transport system from Ehrlich ascites-tumour cells

1989 ◽  
Vol 262 (1) ◽  
pp. 109-118 ◽  
Author(s):  
J R Hammond ◽  
R M Johnstone
Keyword(s):  
Transport System ◽  
Human Erythrocyte ◽  
Plasma Membranes ◽  
Nucleoside Transport ◽  
Ehrlich Cell ◽  
Ascites Tumour ◽  
Ehrlich Ascites ◽  
Ehrlich Ascites Tumour ◽  
Ascites Tumour Cells ◽  
Ehrlich Ascites Tumour Cells

Uptake of [3H]uridine by Ehrlich cells was mediated by both nitrobenzylthioinosine (NBMPR)-sensitive (75%) and NBMPR-insensitive (25%) mechanisms. Each cell contained approx. 26,000 high-affinity (KD = 0.19 nM) recognition sites for [3H]NBMPR, and binding was inhibited by dipyridamole and adenosine at concentrations similar to those required for inhibition of [3H]uridine uptake. Calculations show that each cell contains a total of about 35,000 nucleoside transporters. Photoaffinity labelling of a partially purified preparation of plasma membranes with [3H]NBMPR resulted in a single broad 3H-labelled band on SDS/polyacrylamide gels, with an apparent molecular-mass peak of 42 kDa. This is in contrast with human erythrocyte membranes, where [3H]NBMPR photolabelled two broad bands with peaks at 55 and 80 kDa. Treatment of photoaffinity-labelled membranes with endoglycosidase F decreased the apparent molecular masses of both the Ehrlich-cell and erythrocyte [3H]NBMPR-labelled proteins to approx. 40 kDa. These results suggest that the human erythrocyte [3H]NBMPR-binding polypeptides are more extensively glycosylated than the corresponding Ehrlich-cell polypeptides. Octyl beta-D-glucopyranoside [1.0% (w/v) + asolectin] solubilized over 90% of the [3H]NBMPR-binding sites, with near-complete retention of [3H]NBMPR-binding characteristics. The only major change was a 65-fold decrease in affinity for dipyridamole, which was partly reversed upon incorporation of the solubilized proteins into asolectin membranes. Proteoliposomes, prepared by using asolectin and the octyl glucoside-solubilized plasma membranes, were capable of accumulating [3H]uridine via a protein-dependent dipyridamole/nitrobenzylthioguanosine/dilazep-sensitive mechanism. We have thus demonstrated the efficient solubilization and functional reconstitution of a nucleoside-transport system from Ehrlich ascites-tumour cells.

scholarly journals Uptake of Ca2+ and refilling of intracellular Ca2+ stores in Ehrlich-ascites-tumour cells and in rat thymocytes

1990 ◽  
Vol 271 (2) ◽  
pp. 535-540 ◽  
Author(s):  
M Montero ◽  
J Alvarez ◽  
J Garcia-Sancho
Keyword(s):  
Plasma Membrane ◽  
Tumour Cells ◽  
Ehrlich Cell ◽  
Ascites Tumour ◽  
Ehrlich Ascites ◽  
Filling Time ◽  
Ehrlich Ascites Tumour ◽  
Order Of Magnitude ◽  
Ascites Tumour Cells ◽  
Ehrlich Ascites Tumour Cells

We have studied the uptake of Ca2+ and its redistribution between the cytoplasm and the intracellular stores in Ehrlich-ascites-tumour cells and rat thymocytes previously depleted of Ca2+ by incubation in Ca2(+)-free medium. Measurements included changes of the cytoplasmic Ca2+ concentration ([Ca2+]i), uptake of 45Ca2+ and uptake of Mn2+, a Ca2+ surrogate for Ca2+ channels. Refilling of the Ca2+ stores in thymocytes was very fast (half-filling time: 4 s at 37 degrees C) and very sensitive to temperature (10 times slower at 20 degrees C). It was always preceded by increase of [Ca2+]i. In the Ehrlich cell, both refilling and increase of [Ca2+]i were about one order of magnitude slower. The increase of [Ca2+]i and the refilling of the intracellular stores were both almost completely blocked by Ni2+ in thymocytes, but only partially in the Ehrlich cell. The rates of 45Ca2+ and Mn2+ uptake varied consistently with temperature and the kind of cell. These results suggest that the intracellular stores are refilled by Ca2+ taken up from the cytoplasm. We also find that filling of the Ca2+ stores decreases by about 90% the rate of Mn2+ uptake in thymocytes. This is direct evidence of modulation of the plasma-membrane Ca2+ entry by the degree of filling of the intracellular stores. This modulation occurs in the absence of agonists, suggesting some kind of signalling between the intracellular stores and the Ca2+ entry pathways of the plasma membrane.

scholarly journals The transport and oxidation of succinate by Ehrlich ascites-tumour cells

1976 ◽  
Vol 160 (1) ◽  
pp. 121-123 ◽  
Author(s):  
T L Spencer
Keyword(s):  
Ph Dependence ◽  
Organic Anion ◽  
Tumour Cells ◽  
Cell Integrity ◽  
Carrier System ◽  
Ascites Tumour ◽  
Ehrlich Ascites ◽  
Ehrlich Ascites Tumour ◽  
Ascites Tumour Cells ◽  
Ehrlich Ascites Tumour Cells

The transport and oxidation of succinate by functionally intact Ehrlich ascites-tumour cells was investigated. On the basis of pH dependence and inhibitor sensitivity it was concluded that succinate may be transported across the cell membrane by the organic anion carrier system. Thus the ability of isolated Ehrlich cells to oxidize succinate is real, and is not necessarily a result of damage to cell integrity.

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