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Torocyte shaped endovesicles with a low relative volume were induced in human erythrocytes by polyethyleneglycol dodecylether (C12E8). It is suggested that the torocyte endovesicles are formed in a process where an initially stomatocytic invagination loses volume while maintaining its large surface area. The boundaries of the phase diagram of the observed torocytes are described.
Our study concerns the effects of exposure to lead chloride on the morphology, K+ efflux, SO4 − influx and GSH levels of the human erythrocyte. Blood was collected in heparinized tubes and washed three times. The cells were suspended at 3% hematocrit and incubated for 1 h at 25°C in a medium containing increasing concentrations of lead chloride (0, 0.3, 0.5 and 1 μM). After incubation, the suspensions were centrifuged and the erythrocyte pellets were divided into three aliquots for testing. The results show: an increase in the permeability of erythrocytes treated with lead chloride with consequent damage and cellular death, especially in the presence of high concentrations; an increase in potassium ion efflux; alterations in the morphology and membrane structure of the red blood cells; and a decrease in sulphate uptake, due either to the oxidative effect of this compound on the band 3 protein, which loses its biological valence as a carrier of sulphate ions, or to a decrease in the ATP erythrocyte concentration. In conclusion, the exposure of erythrocytes to Pb2+ ions leads to a reduction in the average lifetime of the erythrocytes and the subsequent development of anemia. These data are discussed in terms of the possible effect of lead on the reduction-oxidation systems of the cell. Oxidant agents, such as lead, are known to cross-link integral membrane proteins, leading to K/Cl-cotransport. The increased K+ efflux affects the altered redox state.
The effectiveness of penetration of erythrocyte membrane by sodium salt of 2,4-dichlorophenoxyacetic acid was analyzed. The experiment was executed in a dependence on different doses of the herbicide and at different times of incubation of red blood cells with 2,4-D-Na. It is known that the main mechanism of detoxification of the cell from xenobiotics including 2,4-D is to bind them with proteins contained in blood plasma. In the case of exposure of blood to high doses of 2,4-D-Na, the unbound part of xenobiotics may penetrate into erythrocytes and change the activity of numerous parameters of the cells. The results obtained by the use of high pressure liquid chromatography (HPLC) revealed that 2,4-D-Na is adsorbed by erythrocytes of 5% haematocrite in the amount of ~1% of the initial concentration. Moreover, it was observed that 2,4-D-Na is capable of accumulating in erythrocyte’s membrane and haemolysate in the amounts of 0.15% and 1.23% of the initial concentration, respectively. It was also stated that penetration of 2,4-dichlorophenoxyacetic acid into erythrocytes is not associated with incubation time (the similar concentrations of 2,4-D-Na were detected after different incubation times of 0.5 to 3 hours); however, it was related with concentrations of the herbicide. We suggest that 2,4-D-Na was transported with concentration gradient in human erythrocytes.
Human erythrocytes were incubated at alkaline pH. In samples equilibrating within 60 min to pH 11 erythrocytes underwent prelytic vesiculation (fragmentation). Erythrocytes developed large (diameter often 1-2 µm) hemoglobin-filled blebs which could be released to the outer medium as hemoglobin containing vesicles. It is suggested that the described vesiculation at high pH occurs due to an uncoupling of the membrane skeleton from the lipid bilayer. Due to the uncoupling from the skeleton the erythrocyte lipid bilayer may behave similar to the membrane of a giant lipid vesicle.
The last step of detoxification of both endogenous and environmental toxicants is typically a conjugation that produces a bulky hydrophilic molecule. The excretion of such conjugates out of cells is of sufficient biological importance to have led to the evolution of ATP-driven export pumps for this purpose. The substrate specificity of such transporters is broad, and in some cases it has been shown to include not only anionic conjugates but also neutral or weakly cationic drugs. In the present article, we review the molecular identity, functional and structural characteristics of these pumps, mainly on the example of human erythrocytes, and discuss their physiological role in detoxification and in the multidrug resistance phenotype of cancer cells.
Multidrug resistance (MDR) of tumour cells is related to the overexpression of ATP-dependent pumps responsible for the active efflux of antitumour agents out of resistant cells. Benzoperimidine and anthrapyridone compounds exhibit comparable cytotoxic activity against sensitive and MDR tumour cells. They diffuse extremely rapidly across the plasma membrane and render the ATP-dependent efflux inefficient. Such uptake could disturb an energy metabolism of normal cells possessing an elevated level of ATP-dependent proteins, especially erythrocytes having a high level of the MRP1, MRP4 and MRP5 proteins. In this study the effect of five antitumour agents: benzoperimidine (BP1), anthrapyridones (CO1, CO7) and reference drugs used in the clinic: doxorubicin (DOX) and pirarubicin (PIRA), on the energetic state in human erythrocytes has been examined. These compounds have various types of structure and kinetics of cellular uptake (slow - DOX, CO7, moderate - PIRA, fast - BP1, CO1) resulting in their different ability to saturate ATP-dependent transporters. The energetic state of erythrocytes was examined by determination of purine nucleotide contents (ATP, ADP, AMP), NAD+ and values of adenylate energy charge (AEC) using an HPLC method. It was found that the level of nucleotides as well as the AEC value of erythrocytes were not changed during 24 h of incubation with these agents independently of their structure and ability to saturate ATP-dependent pumps. This is a very promising result in view of their potential use in the clinic as antitumour drugs against multidrug resistant cancers.
High-pressure-induced hemolysis is suppressed by pretreating human erythrocytes at 49°C, or enhanced by pretreatment with trypsin. So, the response of these pretreated cells to a pressure of 200 MPa was examined using flow cytometry. In the case of intact erythrocytes, a major product was fragmented particles. From 49°C-pretreated cells, vesicles were mainly released. Trypsin-pretreated cells mainly produced open ghosts. Additionally, intact erythrocytes, 49°C-pretreated ones, and trypsin-pretreated ones also released at 200 MPa vesicles of diameter 464 ± 9, 259 ± 18, and 574 ± 16 nm, respectively. These results suggest that mother cells, fragmented particles, vesicles, and open ghosts from 200 MPa-treated erythrocytes are easily monitored by flow cytometry and that the size of released vesicles may also be an important factor in high-pressure-induced hemolysis.
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