Ratio In Erythrocyte Membrane Research Articles

Essential fatty acids and Barratt impulsivity in gambling disorder

BackgroundPolyunsaturated fatty acids (PUFA) have been long implicated in the etiopathogenesis of mental illnesses, including disorders characterized by high impulsivity. The objective of most of the studies in this field is to determine the effect of omega-3 supplementation on the impulsive symptoms. In contrast, studies analyzing basal PUFA composition in patients with impulsive behaviors are very scarce, results are not yet conclusive, and to date, no publication has specifically evaluated this in gambling disorder. Therefore, the main purpose of this research is to examine the relationship between basal PUFA composition of plasma and erythrocyte membrane and impulsivity in subjects with gambling disorder.MethodsIt is an observational and cross-sectional study. The sample consisted of fifty-five men with gambling disorder, who voluntarily accepted to participate. Basal composition of PUFA in plasma and erythrocyte membrane was assessed by gas chromatography and mass spectrometry. Trait impulsivity was measured by the Barratt Impulsiveness Scale version 11 (BIS-11).ResultsArachidonic acid (AA)/eicosapentaenoic acid (EPA) ratio in the erythrocyte membrane was negatively correlated with total scores in BIS-11. It was also observed that impulsive gamblers had a higher proportion of EPA and a lower value of AA/EPA and AA/docosahexaenoic acid (DHA) ratio in erythrocyte membrane than non-impulsive gamblers.ConclusionsThese results support the hypothesis that alteration of basal PUFA composition exists in disorders characterized by high impulsivity, although the direction of this is still unknown. Unfortunately, the empirical literature on this field is non-existent at the time and we have no direct means to support or refute these outcomes. Further research is needed to determine the relationship between essential fatty acids and disorders characterized by high impulsivity.

Alkalinization with potassium bicarbonate improves glutathione status and protein kinetics in young volunteers during 21-day bed rest

Physical inactivity is associated with lean body mass wasting, oxidative stress and pro-inflammatory changes of cell membrane lipids. Alkalinization may potentially counteract these alterations. We evaluated the effects of potassium bicarbonate supplementation on protein kinetics, glutathione status and pro- and anti-inflammatory polyunsaturated fatty acids (PUFA) in erythrocyte membranes in humans, during experimental bed rest. Healthy, young, male volunteers were investigated at the end of two 21-day bed rest periods, one with, and the other without, daily potassium bicarbonate supplementation (90mmol×d-1), according to a cross-over design. Oxidative stress in erythrocytes was evaluated by determining the ratio between reduced (GSH) and oxidized glutathione (GSSG). Glutathione turnover and phenylalanine kinetics, a marker of whole body protein metabolism, were determined by stable isotope infusions. Erythrocyte membranes PUFA composition was analyzed by gas-chromatography. At the end of the two study periods, urinary pH was 10±3% greater in subjects receiving potassium bicarbonate supplementation (7.23±0.15 vs. 6.68±0.11, p<0.001). Alkalinization increased total glutathione concentrations by 5±2% (p<0.05) and decreased its rate of clearance by 38±13% (p<0.05), without significantly changing GSH-to-GSSG ratio. After alkalinization, net protein balance in the postabsorptive state improved significantly by 17±5% (p<0.05) as well as the sum of n-3 PUFA and the n-3-to-n-6 PUFA ratio in erythrocyte membranes (p<0.05). Alkalinization during long-term inactivity is associated with improved glutathione status, anti-inflammatory lipid pattern in cell membranes and reduction in protein catabolism at whole body level. This study suggests that, in clinical conditions characterized by inactivity, oxidative stress and inflammation, alkalinization could be a useful adjuvant therapeutic strategy.

Experimental assessment of the efficiency of erythrocyte membrane repair by an extract of the tunic of the ascidian purple sea squirt in carbon tetrachloride poisoning

We present here data from studies of the physiological characteristics and lipid components of erythrocyte membranes in tetrachloride (CCl 4 ) poisoning and correction of changes with a water-ethanol extract of the tunic (sheath) of the ascidian purple sea squirt (Halocynthia aurantium). CCl 4 poisoning was accompanied by increases in the mean volume and diameter of erythrocytes, along with alterations to the phoshoplipid:neutral lipids ratio and the membrane fatty acid composition. During the deprivation period, most of the study parameters remained at the levels recorded after CCl 4 poisoning. Administration of the ascidian tunic extract widened the thresholds of erythrocyte hemolysis resistance and promoted preservation of the lipid components ratio in erythrocyte membranes and their physiological characteristics. The combination of the high biological activity and the low toxicity of the extract suggests potential for creating new, effective formulations based on marine hydrobionts for use in poisoning.

Treatment with n-3 polyunsaturated fatty acids reverses endothelial dysfunction and oxidative stress in experimental menopause

Menopause is associated with endothelial dysfunction and oxidative stress. In this condition, reduced n-3 polyunsaturated fatty acids (n-3 PUFAs) contribute to cardiovascular disease. We investigated whether treatment with n-3 PUFA reverses endothelial dysfunction and oxidative stress in experimental menopause. Thirty female rats underwent either sham-surgery or bilateral ovariectomy or bilateral ovariectomy+oral n-3 PUFA (0.8 g kg-1 day-1 for 2 months).Ovariectomy caused endothelial dysfunction to acetylcholine, which was reversed by superoxide scavenger Tiron. Erythrocyte membrane lipid composition was characterized by reduced n-3 PUFA total content and omega-3 index, and by concomitant increase in n-6:n-3 PUFA ratio. Ovariectomy-related oxidative stress, demonstrated by both enhanced superoxide production and 3-nitrotyrosine expression in aorta, was associated with increased nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit NOX-4 protein expression. Endothelial nitric oxide synthase (eNOS) functional inhibition by l-NG-nitroarginine methyl ester, protein expression and activity did not change.In ovariectomized rats, treatment with n-3 PUFA increased n-3 PUFA total content and omega-3 index and decreased n-6:n-3 PUFA ratio in erythrocyte membrane, reversed vascular oxidative stress, endothelial dysfunction, aortic 3-nitrotyrosine and markedly lowered NOX-4 protein expression; eNOS protein expression also increased, paralleled by reversal of inhibitory binding to Caveolin-1, while ex-vivo functional inhibition and NOS synthesis were unchanged.These findings demonstrate in vivo a therapeutic benefit of n-3 PUFA on menopause-associated endothelial dysfunction by reversal of alterations in membrane lipid composition induced by ovariectomy and by reduction of vascular oxidative stress. In this setting they also identify NOX-4 as a potential target to reduce oxidative stress-mediated vascular complications.

The Relationships between Erythrocyte Membrane n-6 to n-3 Polyunsaturated Fatty Acids Ratio and Blood Lipids and C-reactive Protein in Chinese Adults: An Observational Study

Objective To investigate the relationships between erythrocyte membrane n-6:n-3 PUFAs ratio and blood lipids and high sensitivity C-reactive protein (hs-CRP). Methods The observational study consisted of a population-based cross-sectional study of 456 Chinese and a subsequent 1-year follow-up study of 171 subjects with the fasting plasma total cholesterol of 5.13-8.00 mmol/L. Results In the cross-sectional analysis, plasma low-density lipoprotein cholesterol (LDL-c) had a significant and negative association with the erythrocyte membrane n-6:n-3 PUFAs ratio ( P for trend=0.019) after adjusting for sex, age and total PUFA percentage. In the follow-up study, 171 subjects were categorized into quartiles by the changes of n-6:n-3 ratio in erythrocyte membrane (Δ=month 12-month 0). In the top quartile whose ratios of n-6:n-3 increased by an average of 1.25 during the follow-up, the LDL-c-lowering extent was 3.3 times of that in the lowest quartile whose ratios of n-6:n-3 decreased by an average of 1.13 (−1.07 mmol/L v.s. −0.32 mmol/L). The hsCRP decreased by 0.11 mg/dL in the lowest quartile while increasing by 0.10 mg/dL in the top quartile ( P for difference=0.052). Conclusion Our results suggested that the balance between n-6 and n-3 fatty acids may optimize the cardiovascular benefits from dietary PUFAs.

Sterol profiles in plasma and erythrocyte membranes in patients with Smith-Lemli-Opitz syndrome: a six-year experience

This study reports our experience over the last six years in the diagnosis of Smith-Lemli-Opitz syndrome and other inborn errors of cholesterol biosynthesis. Gas chromatography/mass spectrometry was used to obtain sterol profiles in plasma and erythrocyte membranes of suspected patients. Plasma sterol reference values calculated in unaffected subjects (n=276) were in agreement with those previously reported. Among patients investigated from 2005 to 2010, we report 16 patients affected by Smith-Lemli-Opitz syndrome, three of whom represent new cases and 13 of whom were follow-up patients. In this period we also identified a new case of chondrodysplasia punctata 2 X-linked. The estimated incidence obtained for Smith-Lemli-Opitz syndrome was 1:93 suspected patients (1.08%). We also studied the effect of storage on the dehydrocholesterols/cholesterol ratio in plasma and erythrocyte membranes of patients affected by Smith-Lemli-Opitz syndrome stored at -20°C for up to 22 and 20 months, respectively. A significant negative linear correlation between storage time and the dehydrocholesterols/cholesterol ratio was identified in both plasma and erythrocyte membranes. The decrease in the dehydrocholesterols/cholesterol ratio in erythrocyte membranes was at least two-fold higher than in plasma. The results of this study may be helpful for diagnosis and interpretation of data in patients with findings suggestive of a cholesterol biosynthesis defect.

Decreased activity of desaturase 5 in association with obesity and insulin resistance aggravates declining long-chainn-3 fatty acid status in Cree undergoing dietary transition

Emerging evidence shows that desaturase 5 (Delta5), the key regulator in the synthesis of highly unsaturated long-chain fatty acids (HUFA), is modulated by factors including adiposity, diet and insulin resistance. We explored the association of these factors in a cross-sectional study within a high-risk Cree population. Anthropometric measures and fasting blood glucose and insulin were analysed. Delta5 was estimated as the 20 : 4n-6:20 : 3n-6 ratio in erythrocyte membranes. The setting of the present study was the Mistissini community in the Cree Territory of Québec, Canada with ninety-eight female and sixty-eight male subjects aged 20-88 years. Obesity (BMI > or = 30 kg/m2) was prevalent across age groups. Delta5 was inversely associated with BMI (Spearman's correlation coefficient (rs) - 0.175; P = 0.03) and positively associated with age (rs 0.593; P < 0.0001), which was driven by age-related increases in dietary intake of n-3 fatty acids and decreases in 20 : 3n-6. Homeostasis model assessment of insulin resistance (HOMA-IR) was significantly inversely associated with Delta5 in age-adjusted linear regression analyses in normoglycaemic individuals (beta - 2.110 (SE 0.566); P < 0.001), whereas no association was observed among glucose-intolerant individuals (interaction term P = 0.03). In contrast, there were no significant interactions indicating differences in the slope for each of the adiposity measures in their associations with Delta5. The present study indicates that the dietary transition of reduced consumption of fish among younger Cree may compound the effects of obesity and emerging insulin resistance which, in turn, could reduce bioavailability of HUFA n-3 (through reduced Delta5 activity). Also, the study suggests that disease progression is an important consideration when evaluating correlates of Delta5 activity in observational studies.

Prophylactic effects of omega-3 polyunsaturated fatty acids and luteolin on airway hyperresponsiveness and inflammation in cats with experimentally-induced asthma

The aim of this study was to assess the preventive effects of omega-3 polyunsaturated fatty acids (omega3 PUFA) and luteolin supplementation on allergen-induced inflammation in eight Ascaris suum (AS)-sensitised cats. Airway responsiveness (AR) tests were performed and venous blood and bronchoalveolar lavage fluid (BALF) collected before and following a single (AS-stimulated) allergen exposure, as well as at the end of a 4-week treatment period, which was followed by a second AS-challenge. The omega6/omega3 fatty acid ratio in erythrocyte membranes, BALF cytology, AR to carbachol, and BALF lipoxin A(4) (LXA(4)), an endogenous inhibitor of inflammation, were assessed at each time point. Compared to respective unstimulated values, AS-challenged cats exhibited a significant rise in BALF eosinophil percentage and there was a trend to increased BALF total cell counts, increased AR and reduced BALF LXA(4) concentrations. The significant decrease in the blood omega6/omega3 ratio seen after supplementation demonstrated that omega3 PUFA were efficiently absorbed. No changes in BALF cytology were found between untreated and treated AS-stimulated cats, but BALF LXA(4) levels were significantly elevated and AR significantly decreased following supplement intake. The study suggests that omega3-luteolin supplementation may have some beneficial effects on AR through a LXA(4)-dependent pathway in cats with experimentally-induced asthma.

A diet rich in long chain omega-3 fatty acids modulates satiety in overweight and obese volunteers during weight loss

Long chain omega-3 fatty acids (LC n-3 FA) are considered nutritional factors with a potential to modulate food intake. Thus, the aim of the current study was to determine whether appetite could be affected by LC n-3 FA when included in a calorie-restricted diet to treat overweight or obesity.Appetite was explored in volunteers (31±5 years; BMI: 28.3±1.5kg/m2) during the last 2 weeks of an 8-week energy-restricted balanced diet (weight loss=−5.9±3.1%) providing either a low (<260mg/day; n=112) or a high amount (>1300mg/day; n=121) of LC n-3 FA. Erythrocyte membrane fatty acids were measured to detect diet-related changes in fatty acids and a validated visual analogue scale (VAS) was used to measure hunger sensations directly after and 2h after a test dinner.The LC n-3 FA content in erythrocyte membrane was lower in the low LC n-3 FA group (10.5±2.5% vs. 12.5±2.6%; p<0.001) after the intervention. The VAS assessment revealed lower hunger sensations in the high LC n-3 FA group immediately after the test dinner (fullness: p=0.045) and after 120min (fullness: p=0.008; hunger: p=0.039). Correlation analysis showed a positive relation between n-3FA/n-6 FA ratio in erythrocyte membrane and fullness 2h postprandial (r=0.139; p=0.032).In conclusion, LC n-3 FA intake modulates postprandial satiety in overweight and obese volunteers during weight loss. Further research is needed to investigate whether LC n-3 FA improve compliance to the nutritional treatment of overweight and obesity as well as weight loss maintenance.

EFFECTS OF SAN'O-SHASHIN-TO ON THE ANTIOXIDATIVE MECHANISM IN SPONTANEOUS FAMILIAL HYPERCHOLESTEROLAEMIC RABBITS

We investigated the effects of the Kampo medicine San'o-shashin-to which showed strong antioxidative effects in vitro on antioxidative mechanism in Kurosawa and Kusanagi- hypercholesterolaemic (KHC) rabbits, which are a good model of spontaneous familial hypercholesterolaemia. A 1-g kg−1dose of San'o-shashin-to was administered orally for 24 weeks and changes in plasma lipids, low-density lipoprotein (LDL) oxidation and redox dynamics of α-tocopherol in plasma and erythrocyte membrane were measured in a control group and San'o-shashin-to-treated group. A significant prolongation of the lag time was found in the 12th and 24th week of the experiment in San'o-shashin-to-treated group, indicating antioxidative effects on LDL. At the end of the administration period, the α-tocopherolquinone/α-tocopherol ratio in erythrocyte membrane, which reflects the utilization rate of α-tocopherol was significantly higher in San'o-shashin-to-treated group. There were no significant differences in the two groups with regards to plasma lipids. These results indicate that San'o-shashin-to had antioxidative effects on LDL in vivo and beneficial effects on redox dynamics of α-tocopherol, which is the strongest endogenous antioxidant.

Redox dynamics of alpha-tocopherol in erythrocyte membranes of elderly patients with asymptomatic primary hyperlipidemia.

We investigated the redox dynamics of alpha-tocopherol in plasma and erythrocyte membranes in elderly patients with asymptomatic primary hyperlipidemia divided into three groups (hypercholesterolemia, hypertriglyceridemia and low high-density lipoprotein cholesterol levels) and in healthy elderly subjects to assess the antioxidative status of alpha-tocopherol. alpha-Tocopherol and alpha-tocopherolquinone were determined by high-performance liquid chromatography using a redox detection mode. In the erythrocyte membrane, there was no difference in the alpha-tocopherol concentration between hyperlipidemic and healthy subjects. The alpha-tocopherolquinone/alpha-tocopherol ratio in plasma and erythrocyte membrane, and the alpha-tocopherol in erythrocyte membrane/alpha-tocopherol in plasma ratio were significantly lower in elderly patients with hypercholesterolemia or hypertriglyceridemia. These findings suggest that the uptake ratio in erythrocyte membranes and the antioxidative activity of alpha-tocopherol in both plasma and erythrocyte membranes are decreased in elderly hyperlipidemic patients. These decreases may promote membrane lipid peroxidation or accelerate atherosclerosis.

Age-related change in the alpha-tocopherolquinone/alpha-tocopherol ratio in the rat erythrocyte membrane

alpha-Tocopherol (alpha-Toc), a lipophilic phenolic antioxidant that is localized mainly in the biomembrane, protects cells against oxidation-associated cytotoxicity by prevention of membrane lipid peroxidation, maintenance of the redox balance intracellular thiols and stabilization of the membrane structure. We investigated the age-related changes in redox dynamics of alpha-Toc in plasma and erythrocyte membrane of an elderly (66 weeks old) and young group (10 weeks old). Total, alpha-, beta + gamma-, delta-Toc and alpha-tocopherolquinone (alpha-TocQ) in plasma and erythrocyte membrane were determined by high-performance liquid chromatography (HPLC) with a series of multiple coulometric working electrodes (CWE). Rat venous blood sample was divided into plasma and erythrocyte layers by centrifugation, and then erythrocyte membrane sample was prepared according to the method of Dodge et al. under a stream of nitrogen. In plasma, total and alpha-Toc concentrations were increased, and beta + gamma-, delta-Toc and alpha-TocQ concentrations were decreased age-dependently. In the erythrocyte membrane, total, alpha-TocQ concentrations and three fractions of tocopherols decreased age-dependently. Also, a decrease in the alpha-TocQ/alpha-Toc ratio in erythrocyte membrane was observed in the elderly group. These findings suggest that the alpha-Toc uptake in erythrocyte membrane and utilization rate of alpha-Toc in erythrocyte membrane decline age-dependently. This decline may promote membrane lipid peroxidation. alpha-Toc redox dynamics in erythrocyte membrane were useful to investigate the pathophysiology of aging mechanisms related to oxidative stress.

The cholesterol to phospholipids ratio (C/PL) of the erythrocyte membrane in normotensive, hypertensive pregnant and in cord blood as assessed by a simple enzymatic method.

The study described was conducted to evaluate a simple enzymatic method for the study of the cholesterol/phospholipids ratio in erythrocyte membrane (C/PL) in a group of normal pregnant, of hypertensive pregnant, in non-pregnant controls and in cord blood. Subjects consisted of 28 normotensive pregnant women (NT), 14 women with pregnancy induced hypertension (PIH), 10 non-pregnant normotensive women (Non-Preg) and 14 samples obtained from umbilical cord (C) at delivery from normotensive pregnant. Red blood cells were isolated from heparinated blood samples. Lipids were extracted from erythrocytes by isopropanol/chloroform, without preparation of cell ghosts. Cholesterol content was evaluated by cholesterol oxidase and phospholipids were estimated as organic phosphorus in the total lipid extract. We found a significant difference of C/PL between the PIH group and the NT group (1.01, SD 0.11 vs. 0.76, SD 0.10, 95% CI 0.74-0.78; p < 0.001) and the Non-Preg group (0.83, SD 0.11, 95% CI 0.80-0.86; p < 0.001). Cord blood C/PL was significantly elevated with respect to NT (1.25, SD 0.13 vs. 0.76, SD 0.10; p < 0.001). The method was proven to be fast, reliable and of value for the study of the pathophysiology of the alteration of the lipid composition, i.e., the increased cholesterol content, of the red cell membrane found in hypertensive pregnant patients.

Erythrocyte alterations correlate with CCl 4 and biliary obstruction-induced liver damage in the rat

Erythrocyte and hepatocyte plasma membranes derived from CCl 4-cirrhotic and bile duct lagated rats were studied. Six groups of animals were used: Group 1 received CCl 4 for 8 weeks. Animals in group 2 received CCl 4 for 12 weeks. Group 3 consisted in animals that received CCl 4 for 8 weeks and then only vehicle for 4 weeks more. Group 4 was the control which received only vehicle. In group 5, obstructive jaundice was induced by bile duct ligation (BDL); animals in group 6 were operated without ligation of the bile duct (sham operated). The activity of Na +/K + and Ca 2+ dependent ATPases, as well as the cholesterol/phospholipid ratio (CH/PL) were determined in both, erythrocyte and hepatocyte plasma membranes. In the CCl 4 groups, Na +/K + and Ca 2+-ATPases activity was decreased about 60–70% while the CH/PL ratio was increased significatively in both, erythrocyte and hepatocyte plasma membranes. Discontinuation of CCl 4 treatment reverted the enzymatic and lipidic alterations to normal in both cell types. ATPases activity and CH/PL ratio in erythrocyte resembled to those of hepatocytes in BDL rats. A strong correlation (p < 0.005) was found when erythrocyte ATPases activity and CH/PL ratio were compared with those of hepatocytes. Moreover, histopathological analysis of liver sections correlated well with both, erythrocyte and hepatocyte biochemical findings. We concluded that determination of ATPases activity and CH/PL ratio in erythrocyte membranes could be a simple, safe and useful marker of cell liver damage in CCl 4-induced liver cirrhosis and biliary obstruction in the rat.

Increased proteolytic activity of erythrocyte membrane in spur cell anaemia

In a case of ‘spur cell anaemia’(SCA) a reduced esterified/free cholesterol ratio was found in plasma, in LDL and HDL fractions, and an increased cholesterol/phospholipid (C/PL) molar ratio in erythrocyte membrane. Cation transport was normal with the exception of Li‐Na counter‐transport which was decreased. An increased intrinsic membrane proteolytic activity (IMPA) was demonstrated by the generalized reduction or, sometimes, disappearance of protein bands on SDS‐PAGE in patient ghosts when the proteolysis was allowed. This characteristic was found to be transferable to normal cells by incubation in SCA‐plasma; moreover membrane C/PL molar ratio was augmented after incubation. Normal plasma was not able to normalize IMPA of SCA cells ‘in vitro’, even if it induced a remarkable decrease of membrane C/PL molar ratio. Nevertheless IMPA normalization did occur ‘in vivo’, when the SCA cells were exposed to therapeutic ‘plasma exchange’(3.3 litre/week). The results suggest the following conclusions: (a) in our SCA patient there is an increased IMPA; (b) this feature, as well as membrane lipid alteration, is transferable to normal erythrocytes; (c) this case seems to demonstrate, for the first time in our knowledge, a modulating effect of plasma on IMPA in erythrocytes.

Increased erythrocyte stearic acid desaturation in rats with chemically induced colorectal carcinomas.

Our previous studies have demonstrated a desaturation of stearic acid related to oleic acid in the lipid layer of erythrocytes in patients with malignancies. This study investigated the stearic acid desaturation in red blood cell membranes of rats during the induction of colorectal tumours. Male Sprague-Dawley rats were injected weekly with dimethylhydrazine (DMH) and sacrificed at 4-week intervals. Blood was withdrawn via heart puncture, collected in EDTA bottle and erythrocytes separated by centrifugation. Total lipid extraction was carried out and analysed with gas liquid chromatography. In the control rats (injected with normal saline) the mean of the stearic to oleic acid ratio in erythrocyte membranes was 2.0 +/- 0.3 (n = 28, range 1.51-2.62) compared to a mean of 0.94 +/- 0.16 (n = 0.5-1.23) in tumour bearing rats (p less than 0.001). The increased desaturation occurred in parallel with appearance of tumours. These data suggest the regulation of stearic acid desaturation is an important adaptive mechanism of membrane fluidity and could be a useful chemical marker for malignancy.

Decreased membrane fluidity and beta-adrenergic responsiveness in atherosclerotic quail

The effects of increased cholesterol on erythrocyte membrane fluidity and beta-adrenergic function were studied in a quail model of atherosclerosis. Birds fed a cholesterol-supplemented diet developed severe atherosclerosis and hypercholesterolemia after 6 wk. This cholesterol-enriched diet led to a markedly elevated serum cholesterol and a 26% increase in the cholesterol-to-phospholipid ratio in erythrocyte membranes. Electron paramagnetic resonance spectra measured with 5- and 12-doxyl-stearic acid spin-label probes were used to estimate the order of quail erythrocyte membranes. Membrane preparations from cholesterol-fed birds were more highly ordered near the membrane leaflet surface, as well as deeper in the membrane interior, compared with controls. beta-Adrenergic receptor stimulation of adenosine 3',5'-cyclic monophosphate accumulation was blunted in erythrocytes from the hypercholesterolemic quail. There was no change in beta-receptor density or affinity in the cholesterol-enriched membranes. These studies demonstrate that cholesterol incorporation into erythrocyte membranes in vivo is associated with decreased membrane fluidity and decreased beta-adrenergic responsiveness. The atherosclerotic quail may serve as a useful model to further probe the sequelae of hypercholesterolemia on the function of integral membrane proteins.

Differences in membrane lipid composition and fluidity of transplanted grsl lymphoma cells, depending on their site of growth in the mouse

GRSL lymphoma cells were isolated from various growth sites in the host. The relative membrane lipid fluidities of these cells and of normal lymphoid cells were estimated by fluorescence polarization, using the probe diphenylhexatriene and by measuring the (free) cholesterol/phospholipid molar ratio in whole cells. The results indicate that the membrane fluidity (reciprocal of the lipid structural order) of the lymphoma cells increases in the order of their location: peripheral blood < spleen < mesenterial lymph node < ascites fluid. The membrane fluidities of normal lymphocytes from thymus, mesenterial lymph node and spleen were about the same, but higher than of peripheral blood lymphocytes, and between those of the lymphoma cells from lymph node and spleen. These results are confirmed by more extensive analysis on purified plasma membranes from the splenic and ascitic GRSL lymphoma cells and from normal splenocytes and thymocytes. The significantly higher lipid order parameter found in the GRSL plasma membrane isolated from the spleen as compared to those from the ascites cells could be fully explained by the differences measured in the major chemical determinants of the fluidity, i.e., the cholesterol/phospholipid ratio, the sphingomyelin content and the degree of saturation of the fatty acyl groups of the phospholipids. It was also found that the cholesterol/phospholipid ratio in erythrocyte membranes isolated from the peripheral blood of the tumor bearers was higher than in those from normal control mice. The observed differences in membrane fluidity between distinct subsets of tumor cells may be relevant to the sensitivity of these cells to immune attack or to drugs.