Aging human erythrocytes. Differential sensitivity of young and old erythrocytes to hemolysis induced by peroxide in the presence of thyroxine

Effects of propofol, a sedative-hypnotic drug, on the lipid profile, antioxidant indices, and cardiovascular marker enzymes in wistar rats

In recent years, the activity of anaesthetic propofol on biological processes has been attracting attention. The effect of propofol on biochemical indices in animals is unknown. In this study, we examined the effects of propofol on lipid profile, antioxidant indices, and cardiovascular marker (CVM) enzymes in rats. The study consists of three groups of seven rats each. Group one received corn oil (Control) while groups two and three received propofol (doses of 2 and 4 mg/kg body weight, resp.). Results showed that administration of propofol caused a significant (P < 0.05) and dose-dependent increase in the levels of total bilirubin. Propofol at 2 and 4 mg/kg increased the levels of serum total cholesterol by 74% and 55%, triglycerides by 97% and 115%, and LDL-C (low-density lipoprotein-cholesterol) by 45% and 73%, respectively, while HDL-C (high-density lipoprotein-cholesterol) decreased by 41% and 54%, respectively. Propofol significantly (P < 0.05) increased the levels of the hepatic reduced glutathione (GSH) and activities of GSH-dependent enzymes. Propofol at 2 and 4 mg/kg increased the activities of CVM enzymes: lactate dehydrogenase by 1.7 and 1.8 folds and creatinine phosphokinase by 2.0 and 2.1 folds, respectively. Taken together, propofol increased the levels of GSH and GSH-dependent enzymes but adversely affected the lipid profile of the rats.

Studies on the toxicological effect of nevirapine, an antiretroviral drug, on the liver, kidney and testis of male Wistar rats

We investigated the toxic effect of nevirapine (NVP; Viramune®), an antiretroviral drug, on the liver, kidney and testis of Wistar rats. Twenty-one rats were assigned into 3 groups of 7 animals each. The first group served as control, and the second and third groups received NVP at 18 and 36 mg/kg body weight, respectively. Clinical signs of toxicity were not observed in the animals. NVP at both doses did not significantly ( p > 0.05) alter the body weight gain, relative weights of kidney and testis, serum protein, urea, creatinine and alkaline phosphatase levels of the animals. However, NVP2 significantly ( p < 0.05) increased the relative weight of liver, level of serum total bilirubin and activities of γ-glutamyl transferase, alanine and aspartate aminotransferases. NVP administration caused a dose-dependent, significant ( p < 0.05) elevation of lipid peroxidation measured as malondialdehyde (MDA) content in the liver, kidney and testis of the rats. Hepatic, renal and testicular MDA were increased by 107%, 80% and 163%, respectively, in NVP2-treated rats. Elevation in MDA was accompanied by a significant ( p < 0.05) decrease in the activities of hepatic, renal and testicular superoxide dismutase and catalase. NVP2 caused 43% and 32% decrease in spermatozoa motility and live/dead sperm count, respectively, and 94% increase in total sperm abnormalities. Histopathological findings showed that NVP2 caused degeneration of seminiferous tubules in testis, and severe necrosis in liver slides. NVP induced oxidative stress with corresponding decrease in antioxidant status of the rats. The changes in sperm parameters and, elevation of liver marker enzymes suggest an interference of NVP2 with these organs.

Lead exposure increases oxidative stress in the gastric mucosa of HCl/ethanol-exposed rats

AIM: To investigate the role of reactive oxygen species in the ulcer-aggravating effect of lead in albino rats.

METHODS: Albino Wistar rats were randomly divided into three groups and treated orally with 100 mg/L (low dose) or 5000 mg/L (high dose) of lead acetate for 15 wk. A third group received saline and served as control. At the end of wk 15, colorimetric assays were applied to determine the concentrations of total protein and nitrite, the activities of the oxidative enzymes catalase and superoxide dismutase, and lipid peroxidation in homogenized gastric mucosal samples.

RESULTS: Exposure of rats to lead significantly increased the gastric mucosal damage caused by acidified ethanol. Although the basal gastric acid secretory rate was not significantly altered, the maximal response of the stomach to histamine was significantly higher in the lead-exposed animals than in the unexposed control group. Exposure to low and high levels of lead significantly increased gastric lipid peroxidation to 183.2% ± 12.7% and 226.1% ± 6.8% of control values respectively (P < 0.0). On the other hand, lead exposure significantly decreased catalase and superoxide dismutase (SOD) activities and the amount of nitrite in gastric mucosal samples.

CONCLUSION: Lead increases the formation of gastric ulcers by interfering with the oxidative metabolism in the stomach.

Oxidation sensitivity may be a useful tool for the detection of the hematotoxic potential of newly developed molecules: application to antipsychotic drugs

Some antipsychotic agents have been found to produce agranulocytosis and aplastic anemia. The oxidation phenomena and/or the formation of free radicals has been suggested to be causally related to various hematological disorders, e.g., agranulocytosis. Using five experimental conditions, we tested the oxidative potential of compounds with and without a history of hematological side effects, e.g., agranulocytosis and aplastic anemia. A statistical analysis was undertaken for each experimental condition and a multivariate analysis combining all results was performed. Two peroxidase-induced free radical models did not successfully discriminate between drugs with and without a history of causing hematologic problems (<70%). The lipid peroxidation system provided even less satisfactory discrimination, with only 56.25% correct classification. However, an 87.5% correct classification was obtained when using the oxidation potentials of these drugs determined at pH 4.7 and at pH 7.4. A multivariate analysis taking into account the five variables provided 87.5% success in classification. The two clusters were better discriminated in terms of a "distance coefficient." In a second analysis, the putative antipsychotic pyridobenzodiazepine analogues (JL5, JL8, JL18, and JL25) were classified in the cluster of toxic compounds, while the oxa- and thiazepine analogues (JL2, JL3, and JL13) were classified as nontoxic compounds. On the other hand, a few metabolites of clozapine and fluperlapine were classified in the toxic compound group. The procedure described herein is, to our knowledge, the first which classifies molecules of different structures as well as different pharmacological profiles according to their hematotoxic potential. Such a procedure could be used to predict drug-induced hematological side effects.

JL 13, a potential successor to clozapine, is less sensitive to oxidative phenomena

The oxidation behaviour of JL 13, a promising antipsychotic, was investigated in comparison with clozapine and loxapine, by measuring their direct "radical scavenging" abilities and their efficacies in inhibiting the lipid peroxidation. In the lipid peroxidation system, the reactivity of these compounds with free radicals produced by gamma-irradiation of linoleic acid may be presented as follows: JL 13 = loxapine < clozapine. In two enzymatic systems (HRP/GSH and HRP/H2O2/ GSH) which generate the thiyl free radicals, clozapine produces a strong enhancement of the thiyl-radical EPR signal intensity while JL 13 and loxapine exhibit no or minimal effect on this signal. The redox potential values for the three derivatives confirm the spectro-photometric and EPR results. Following this study, we show that JL 13, although presenting a preclinical clozapine-like profile, appears less sensitive to oxidation than clozapine.

The effects of pH on the oxidation of low-density lipoprotein by copper and metmyoglobin are different

The amplification of low-density lipoprotein (LDL) peroxidation in vitro by copper and myoglobin are well-studied biochemical approaches for investigating the oxidative modification of LDL and its role in the pathogenesis of atherosclerosis. Since the acidity of the environment is increased in inflammatory sites, the aim of this study was to investigate the effects of acidic pH on the oxidisability of LDL mediated by the haem protein myoglobin in comparison with that of copper-mediated LDL oxidation. The results show that acidic pH enhances myoglobin-mediated LDL oxidation as measured by conjugated dienes, lipid hydroperoxides and electrophoretic mobility, whilst a retardation is observed with copper as pro-oxidant; the mechanism probably relates to the effects of pH on the decomposition and formation of lipid hydroperoxides and the relative influences of copper ions and of myoglobin under these conditions.

The antioxidant properties of theaflavins and their gallate esters--radical scavengers or metal chelators?

The antioxidant properties of theaflavins and their gallate esters were studied by investigating their abilities to scavenge free radicals in the aqueous and lipophilic phases. The total relative antioxidant activities in the aqueous phase were assessed by measuring their direct ABTS.+ radical scavenging abilities, and by their efficacies in inhibiting the degradation of deoxyribose induced by iron. The propensities for enhancing the resistance of LDL to oxidation mediated by Cu2+ were also measured. The results show that the hierarchy of reactivity of these compounds as antioxidants is: theaflavin digallate > 3'-monogallate = 3-monogallate > theaflavin. Spectroscopic studies show that all the compounds chelate iron and copper; enhanced absorbance in the visible region is observed in the case of the iron-digallate complex, but not with copper.

Antioxidant potential of intermediates in phenylpropanoid metabolism in higher plants

In this study the antioxidant activities of the hydroxycinnamic acids, chlorogenic, caffeic, ferulic and p-coumaric, have been investigated in peroxidising lipid systems mediated by metmyoglobin. The results show that the order of effectiveness in increasing the resistance of LDL to peroxidation, in protecting LDL cholesterol from oxidation and preventing the oxidative modification of the LDL apoprotein B100 is caffeic = chlorogenic > ferulic > p-coumaric acid. Assessment of the rates of reaction of the hydroxycinnamates with ferrylmyoglobin, a product of the reductive decomposition of lipid hydroperoxides, reveals that the compounds are more effective as peroxyl radical scavengers than reductants of ferryl myoglobin in peroxidising LDL systems mediated by haem proteins.

Inhibition of copper-mediated low density lipoprotein peroxidation by quinoline and indolinone nitroxide radicals

Quinoline and indolinone nitroxide radicals are known to be efficient scavengers of oxygen-centred (rate constants (k) between 10(3) and 10(5)/M/sec) and carbon-centred radicals (almost diffusion-controlled rate). In this study, the relative effects of these compounds in protecting low density lipoprotein (LDL) from oxidation induced by copper have been investigated. The extent of lipid peroxidation was assessed by monitoring the increased conjugated diene formation, the altered surface charge of the apolipoprotein B and the generation of aldehydic breakdown products of oxidized LDL. All the nitroxides inhibited LDL peroxidation in a concentration-dependent manner. The corresponding hydroxylamines of the nitroxides were also studied and were shown to inhibit lipid peroxidation to almost the same extent as the parent nitroxide. The data indicates that this class of nitroxide radicals (and their reduced hydroxylamine forms) are effective lipophilic antioxidants with the quinoline nitroxide being more efficient than the indolinone nitroxides.

Ruptured erythrocytes inhibit the oxidation of membranes by 15-hydroperoxy-eicosatetraenoic acid

In this study, the pro-oxidant effects of the hydroperoxide, 15-hydroperoxy-eicosatetraenoic acid (15-HPETE), on erythrocyte membranes and the modulation of the oxidation by haem proteins released from ruptured erythrocytes have been assessed. The results indicate that ruptured erythrocytes may act as an antioxidant in protecting membranes against oxidative stress induced by hydroperoxides and that it is the oxyhaemoglobin that is the active constituent of the protective mechanism. An important feature of the mechanism is the peroxidatic action of oxyhaemoglobin and its rate of reaction with 15-HPETE.

Oxidised low density lipoproteins induce iron release from activated myoglobin

Recent reports have detected the presence of iron in human atherosclerotic lesions [Biochem. J. 286 (1992) 901-905]. This study provides evidence for a biochemical mechanism whereby iron is released from myoglobin by low density lipoprotein (LDL) which has become oxidised by the ferryl myoglobin species. The haem destabilisation and iron release are inhibited by monohydroxamate compounds and desferrioxamine through their ability to inhibit the propagation of LDL oxidation. Thus, iron may derive from the myoglobin released from ruptured cells in the oxidising environment of the atherosclerotic lesion.

Protective actions of tamoxifen and 4-hydroxytamoxifen against oxidative damage to human low-density lipoproteins: a mechanism accounting for the cardioprotective action of tamoxifen?

Tamoxifen and 4-hydroxytamoxifen protect isolated human low-density lipoproteins (LDLs) against copper-ion-dependent lipid peroxidation: 4-hydroxytamoxifen is more protective than tamoxifen or 17 beta-oestradiol. 4-Hydroxytamoxifen and 17 beta-oestradiol also prevent the increase in the electrophoretic mobility of LDL caused by exposure to copper ions, presumably by protection of the apoprotein B of LDL against oxidative modification. Our observations may help to account for the cardioprotective benefits reported to be associated with tamoxifen therapy and prophylaxis in breast cancer.

The efficacy of monohydroxamates as free radical scavenging agents compared with di- and trihydroxamates

Desferrioxamine, the therapeutic iron chelator, is limited in its usage by its short half-life in plasma and lack of oral activity, its side-effects and its slow penetration into cells. Several studies have emerged recently demonstrating the ability of this trihydroxamate compound to act as a radical scavenger, in addition to and independently of its iron-chelating properties. These include the interaction of desferrioxamine with the superoxide radical and ferryl myoglobin radical, as well as its action as a chain-breaking antioxidant in peroxidizing erythrocyte membranes. We have synthesized recently a series of monohydroxamate compounds and investigated their efficacy as radical scavenging antioxidants in comparison with desferrioxamine and rhodotorulic acid, a naturally occurring dihydroxamate compound. The results show that the relative rates of reaction of these hydroxamate derivatives with ferryl myoglobin are N-methyl-N-hexanoyl hydroxylamine > N-methyl-N-benzoyl hydroxylamine > N-methyl-N-acetyl hydroxylamine > desferrioxamine > rhodotorulic acid > N-methyl-N-butyryl hydroxylamine.

The interaction between ruptured erythrocytes and low-density lipoproteins

Low-density lipoproteins (LDL) are oxidatively modified on interaction with haem proteins. The interaction of ruptured erythrocytes with LDL induces oxidative damage as detected by alterations in electrophoretic mobility and the peroxidation of the polyunsaturated fatty acyl chains. Difference spectroscopy reveals that the amplification of the oxidative process by the haem protein is related to the transition of the oxidation state of the haemoglobin in the erythrocyte lysate from the oxy [X-FeII-O2] to the ferryl [X-FeIV = O] form. The incorporation of the lipid-soluble antioxidant, butylated hydroxy toluene, at specific time points during the LDL-erythrocyte interaction prolongs the lag phase to oxidation and eliminates the oxy-to-ferryl conversion of the haemoglobin. The timescale of this haem conversion is related to the antioxidant status of the LDL.

Thiol compounds as protective agents in erythrocytes under oxidative stress

The potential for the thiol-containing drugs, N-acetyl cysteine and N-mercaptopropionyl glycine, to act as antioxidants intracellularly has been studied in erythrocytes under oxidative stress. The effects have been compared with that of the glutathione peroxidase inhibitor, mercaptosuccinate. The results show differential responses of sickle and normal erythrocytes to the thiol compounds. N-acetyl cysteine is the more efficacious with no toxic effects in these systems. N-Mercaptopropionyl glycine is not only limited in its ability to demonstrate antioxidant capacity in erythrocytes but also exerts deleterious effects.

Identification of initiating agents in myoglobin-induced lipid peroxidation

Reaction of metmyoglobin with peroxides is known to involve the formation, possibly via a porphyrin radical-cation, of a ferryl (iron(IV)-oxo) species and a protein radical; there is a little information available as to which of these species initiates the damage which is observed on incubating membrane fractions with such mixtures. It is shown in this study that the initial protein radical, which is a tyrosine phenoxyl radical centered at position 103 in the protein, does not react rapidly with erythrocyte membranes. However a tyrosine peroxyl radical, formed by addition of oxygen to this species, does react rapidly, and it is concluded that this radical, together with the ferryl species, is an important initiating species in myoglobin-induced lipid peroxidation.

The formation of free radicals by cardiac myocytes under oxidative stress and the effects of electron-donating drugs

The interaction of myoglobin with H2O2 leads via a two-electron oxidation process to the formation of ferryl myoglobin. Metmyoglobin is more readily activated than oxymyoglobin to the ferryl states, which are capable of inducing peroxidative damage to membranes. E.p.r. and optical spectroscopic studies show that the thiol-containing compounds N-(2-mercaptopropionyl) glycine and N-acetylcysteine and the trihydroxamate desferrioxamine attenuate these processes by reducing the ferryl myoglobin species to metmyoglobin, with the formation of thiyl radicals and the desferrioxamine nitroxide radical respectively. Biochemical investigations of the potential for myoglobin in ruptured myocytes to be involved in radical generation, when under oxidative stress, and of the nature of the resulting species, were also undertaken. E.p.r. spectroscopic studies revealed the formation of a radical species which is capable of inducing membrane lipid peroxidation. The interaction of the thiol compounds and desferrioxamine with components of myocardial tissue under these conditions results in the generation of thiol-derived radical species and the desferrioxamine nitroxide radical respectively. These data, along with those obtained using optical spectrocopy, support the assignment of the identity of the radical species generated from the myocytes as the ferryl myoglobin radical.

The suppression of iron release from activated myoglobin by physiological electron donors and by desferrioxamine

Interactions between ferrimyoglobin and hydrogen peroxide have been postulated to lead to the formation of activated ferryl myoglobin. In such systems hydroxyl radical formation has also been demonstrated by its ability to degrade deoxyribose subsequent to the release of iron from the porphyrin ring of the myoglobin. We have investigated the potential for ferrylmyoglobin formation and for iron release from ferrylmyoglobin exposed to hydrogen peroxide; the modulation of the stability of the haem group by membranes and in the presence of desferrioxamine and ascorbate have also been assessed. The results show that iron release from ferrimyoglobin activated by hydrogen peroxide is suppressed in the presence of membranes, apparently by the reduction of the ferryl myoglobin species, and lipid peroxidation occurs. In the presence of desferrioxamine, formation of the ferrylmyoglobin species is suppressed by the electron donating properties of the trihydroxamate moiety, which also functions as a chain-breaking antioxidant when added to peroxidising membranes. The physiological antioxidant ascorbate not only suppresses the formation of the ferryl myoglobin species under the conditions described here, but also reduces the myoglobin iron to the iron II state.

The nature of oxidants and antioxidant systems in the inhibition of mutation and cancer

We briefly review current concepts with regard to the nature of oxygen-derived oxidants in biological systems. Of these substances, hydroxyl radicals derived from hydrogen peroxide seem most likely to be involved in the various stages of carcinogenesis. Hydrogen peroxide detoxification, primarily through glutathione activity, is essential in preventing hydroxyl-radical formation. Transition metals such as iron play a central role in this latter process. Alterations in cellular macromolecules are most likely to take place if hydroxyl-radical formation is directed toward specific intramolecular sites by appropriately sequestered metals. For this reason, repair and turnover events are apt to be more important protective devices than are the actions of molecules which scavenge hydroxyl radicals. Although many cellular constituents are potential targets in free-radical and oxidant attacks leading to carcinogenesis, nucleic acids have been most extensively studied in this connection. On the basis of these investigations, it is a facile conclusion that oxidants might be involved in the early events of carcinogenesis as well as in transformation or promotion. The literature on antioxidants in chemoprevention in animals is supportive of such a role. However, other biochemical effects of antioxidants should raise a note of caution in the interpretation of animal experiments.

Hyperthermic toxicity and the modulation of heat damage to cell protein synthesis in HeLa cells

That some of the effects of hyperthermia on HeLa cell protein synthesis may involve free radical activity is suggested by experiments with free radical scavengers. A possible source of damaging free radicals induced by heat may lie in peroxidative events within lipid-containing membranes. These can be blocked by EGTA. Other experiments with t-butylhydroperoxide indicate that cycloheximide can also neutralise peroxidative effects. These effects are discussed in the light of observations that calcium depletion (or EGTA treatment) can induce thermotolerance and that cycloheximide does not prevent the development of thermotolerance.

Oxidative stress and heat shock protein induction in human cells

Agents which induce heat shock protein synthesis in cultured monolayers of Hela cells such as hyperthermia, ethanol and sodium arsenite can also cause increases in the levels of lipid peroxidation as determined by the formation of TBA-products. The heat induced increases may be diminished by addition to the medium of mannitol or EGTA. These compounds are known to depress heat shock protein synthesis. Following hyperthermia there is also a decrease in protein synthesis. In vitro studies indicate possible damage to ribosomes, and since the heat induced loss of protein synthetic capacity can be increased by superoxide dismutase inhibitors, and prevented by mannitol, such effects may be linked to the increases observed in lipid peroxidation. It is suggested that a connection exists between lipid peroxidation and heat shock protein gene activation.

Sickle cell membranes and oxidative damage

Sickle erythrocytes and their membranes are susceptible to endogenous free-radical-mediated oxidative damage which correlates with the proportion of irreversibly sickled cells. The suppression of incubation-induced oxidative stress by antioxidants, free radical scavengers and an iron chelator suggest that oxidation products of membrane-bound haemoglobin contribute towards the pathology of the disease.

Oxidation of biological membranes and its inhibition. Free radical chain oxidation of erythrocyte ghost membranes by oxygen

The oxidation of human and rat erythrocyte ghost membranes by molecular oxygen has been performed in an aqueous suspension at 37 degrees C. A constant rate of oxygen uptake was observed in the presence of radical initiator. alpha-Tocopherol in the membrane suppressed the oxidation and the induction period was clearly observed. alpha-Tocopherol decreased linearly during the induction period and when it was depleted the induction period was over and a rapid oxidation started. The rate of oxidation was proportional to the square root of the rate of initial radical generation. The kinetic chain length, the ratio of the rate of propagation to that of initiation, was long, ranging from 7 to 100. These results indicate that the erythrocyte ghost membranes are oxidized by a free radical chain mechanism by molecular oxygen. Among the fatty acids of membrane lipids, polyunsaturated fatty acids were oxidized exclusively. Proteins as well as polyunsaturated fatty acids were oxidized and the formation of the high- and low-molecular-weight proteins and the decrease of protein bands were observed on gel electrophoresis.

Superoxide dismutase activity in rabbit reticulocytes

Reticulocytosis was induced in rabbits by bleeding anemia and erythrocyte superoxide dismutase activity was determined. Reticulocytes were found to contain about 1.3 times as much activity as mature erythrocytes.

Levels of lipid peroxidation in hepatocytes isolated from aging rats fed an antioxidant-free diet

Enzymatically isolated hepatocytes were utilized to evaluate levels of lipid peroxidation in young (3 months), adult (12 months) and aged (25 months) Fisher-344 female rats. Lipid peroxidation was measured by assaying levels of malonaldehyde, a by-product of the peroxidation reaction. Young, adult and aged animals were fed a liquid antioxidant-free diet for 21 days prior to the hepatocyte isolation. Cells isolated from young rats demonstrated the highest levels of lipid peroxidation (microgram of malonaldehyde/10(6) cells). This increase may be a result of the isolation procedure or of metabolic differences found in younger animals. When hepatocytes from aged animals on the antioxidant-free diet were incubated in the presence of lipid peroxidation inducers, such as cumene hydroperoxide or NADPH, significant elevations in lipid peroxidation over comparable adult values were observed. Aged hepatocytes appear to be more susceptible to the peroxidation process than adult hepatocytes, possibly due to defective peroxidation defenses.

Calcium potentiates the peroxidation of erythrocyte membrane lipids

To explore the possible role of intracellular calcium in membrane lipid peroxidation, we subjected red cells to conditions designed to increase intracellular calcium levels and then measured lipid peroxidation after exposure to a peroxidant threat. Human erythrocytes were pretreated for 3 h with either very high levels of CaCl2, or with low levels in the presence of the ionophore A23187. The erythrocytes were subsequently exposed to a peroxide-generating system consisting of xanthine and xanthine oxidase, or H2O2 for 1 h at 37 degrees C. As measured by a malonyldialdehyde assay, the calcium-treated cell showed up to a 2-fold increase in lipid peroxidation in comparison to untreated cells. In experiments with the ionophore, calcium concentration-dependent effects were detected at levels as low as 10 microM and were maximal at 50 microM. A significant loss of phosphatidylserine and phosphatidylethanolamine was observed in calcium- and peroxide-treated erythrocytes. This potentiation of membrane lipid peroxidation and lipid loss could be prevented by either lipid antioxidants or EGTA. The present study shows that pretreatment of erythrocytes with calcium increases their sensitivity to lipid peroxidation. This suggests that increased calcium concentration may be a factor in the potentiation of membrane lipid peroxidation of erythrocytes known to have increased calcium levels such as sickled and senescent red cells.

Superoxide dismutase and radiation-induced haemolysis: no benefit of its increased content in red cells

The sensitivity of human erythrocytes with normal and increased activity of superoxide dismutase (SOD) was compared under different types of oxidative stress. Red blood cells with increased SOD activity were more resistant to haemolysis induced by photoactivated riboflavin but no more resistant to radiation-induced haemolysis and acetylphenylhydrazine stress. These results indicate a negligible role of O(2) in mediation of the haemolytic action of ionizing radiation.

Aging of the erythrocyte. I. Increase in the microviscosity of cell interior as determined by the spin label method

By means of the spin labelling technique changes in the microviscosity of the cell interior of density-seperated bovine red blood cells were estimated. An increase in the rotational correlation time of the Tempamine spin label indicated an increase in the microviscosity of the red blood cell interior during in vivo aging. This increase is apparently due to alterations in the electrolyte content and may influence the course of diffusion-limited reactions in the cell.

Increased erythrocyte lipid peroxidation in hereditary xerocytosis

Xerocytosis is a chronic hemolytic anemia with abnormal membrane function manifested by an increase in passive potassium permeability. Xerocytes demonstrate a greater susceptibility to hydrogen peroxide manifested by the production of malondialdehyde (MDA). Xerocyte membrane phospholipid and fatty acid analysis is normal except for a slight increase in phosphatidyl choline, a commensurate decrease in sphingomyelin, as well as a decrease in linoleic acid. Metabolism and glutathione stability are normal as well as plasma vitamin E levels in patients with xerocytosis. The increased susceptibility to oxidant stress is exaggerated in the "older aged" xerocyte population and correlated well with decreased intracellular potassium concentration.