Fatty acid composition of erythrocyte membrane lipid obtained from children suffering from kwashiorkor and marasmus

The fatty acid composition of erythrocyte membrane (EM) lipids obtained from normal, kwashiorkor, and marasmic children was analyzed by gas chromatography. The proportion of palmitic acid (16:0) was lower and of oleic acid (18:1) higher in the kwashiorkor group than in the control group. The marasmic group showed lower proportions of eicosatrienoic acid (20:3) and arachidonic acid (20:4) and a higher proportion of oleic acid (18:1) than the control group. A significant difference was found between the marasmic and kwashiorkor groups with respect to arachidonic acid (20:4), which showed a lower proportion in the former group than the latter. The ratio of arachidonic acid to linoleic acid (20:4/18:2) was markedly lower in the marasmic group than the control group, suggesting a possible impairment in the conversion of linoleic acid to arachidonic acid in marasmic children. The ratio of unsaturated fatty acids to saturated fatty acids was markedly elevated in the kwashiorkor group over that of control group, indicating increased fluidity of EM in kwashiorkor. It is suggested that the altered membrane fatty acid composition reflects deranged lipid metabolism and affects the physical and physiological properties of EM and could contribute to changes in the activities of several red blood cell membrane-bound enzymes reported earlier in kwashiorkor children.     

Platelet and erythrocyte Mg2+, Ca2+, Na+, K+ and cell membrane adenosine triphosphatase activity in essential hypertension in blacks.

OBJECTIVE: To assess the relationship between intracellular Mg2+, Ca2+, Na+ and K+ and cell membrane adenosine triphosphatase (ATPase) activity in normotensive and hypertensive blacks. DESIGN: Intracellular cations and cell membrane ATPase activity were studied in black patients with untreated essential hypertension and age-, weight- and height-matched normotensive controls. Platelet, erythrocyte and serum Mg2+, Ca2+, Na+ and K+ levels as well as platelet and erythrocyte membrane Na+,K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase activities were measured in all subjects. METHODS: Intracellular Na+ and K+ were measured by flame photometry and Mg+ and Ca+ by atomic absorption spectrophotometry. Cell membrane ATPase activity was determined by a colorimetric method. RESULTS: The hypertensive group consistently demonstrated depressed activity of each ATPase studied, with significantly lower serum Mg2+, serum K+, erythrocyte Mg2+ and platelet Mg2+ levels compared with the normotensive group. Platelet Na+ and Ca2+ and erythrocyte Ca2+ were significantly elevated in the hypertensive group. In the hypertensive group, mean arterial pressure (MAP) was inversely correlated with platelet and erythrocyte membrane Na+,K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase. Serum Mg2+, serum Ca2+ and platelet Mg2+ were negatively correlated with MAP in the hypertensive group whilst erythrocyte and platelet Ca2+ were positively correlated. In the normotensive group, platelet Mg2+ and MAP were negatively, and erythrocyte Ca2+ and MAP, positively correlated. CONCLUSIONS: Black patients with essential hypertension have widespread depression of cell membrane Na+,K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase activities with serum and intracellular Mg2+ depletion and cytosolic Na+ and Ca2+ overload, which may reflect an underlying membrane abnormality in essential hypertension. These cellular abnormalities may be related to the defective transport mechanisms that in turn may be aggravated by Mg2+ depletion.     

The Interaction between (Ca2++ Mg2+)-ATPase and the Soluble Activator (Calmodulin) in Erythrocytes Containing Haemoglobin S

In normal erythrocytes, a membrane-bound (Ca2+ + Mg2+)-ATPase is stimulated by a soluble activator, calmodulin. Since cells containing Hb S accumulate excessive Ca2+, the defect could lie in either the (Ca2+ + Mg2+)-ATPase or calmodulin. To decide between these two possibilities, we prepared (Ca2+ + Mg2+)-ATPase from erythrocytes of normal (AA), sickle cell trait (AS) and sickle cell disease (SS) individuals. Calmodulin was prepared from haemolysates from AA and SS erythrocytes. The enzyme prepared from SS ghosts had lower specific activity than that from AA membranes. Furthermore, calmodulin from either source did not stimulate the ATPase of SS erythrocytes. Enzyme from AS cells had specific activity similar to that of enzyme prepared from SS membranes. The enzymatic activity of a mixed cell population obtained from an SS patient 8 d following exchange-transfusion was proportional to the per cent Hb A. These results indicate that calmodulin is unable to interact with the enzyme site on the SS membrane. This inability is believed to be due to a specific property of the membrane and not an abnormality of calmodulin itself.     

Erythrocyte calcium-stimulated, magnesium-activated adenosine 5'-triphosphatase activity in essential hypertension.

OBJECTIVE: The aim of this study was to investigate the basis of reduced erythrocyte calcium-stimulated, magnesium-activated adenosine 5' triphosphatase (Ca2+, Mg(2+)-ATPase) activity in essential hypertension. DESIGN: Experiments were performed to establish whether the reduced erythrocyte Ca2+, Mg(2+)-ATPase activity in patients with essential hypertension, when compared with age- and sex-matched normotensive control subjects, was due to changes in enzyme properties or to an altered membrane environment. METHODS: Erythrocyte membrane Ca2+, Mg(2+)-ATPase activity was determined by measuring ATP-dependent 45Ca2+ uptake in inside-out vesicles and calcium-dependent gamma-32P ATP hydrolysis in ghost membranes, prepared from the same sample of blood. Calcium-dependent gamma-32P ATP hydrolysis activity was also measured in detergent extracts of erythrocyte membranes. RESULTS: In the absence and presence of calmodulin, both ATP-dependent Ca2+ uptake and calcium-dependent ATP hydrolysis activities of erythrocyte membranes prepared from patients with essential hypertension were significantly reduced when compared with normotensive subjects. No difference in calmodulin affinity was observed between hypertensive and normotensive subjects, although the calcium dependence of calmodulin-independent Ca2+ uptake activity in inside-out vesicles was altered. No significant difference in calcium-dependent ATP hydrolysis activity was observed between hypertensive and normotensive preparations after detergent solubilization of erythrocyte membrane proteins. CONCLUSIONS: These results suggest that the number of Ca2+, Mg(2+)-ATPase units is similar in erythrocytes of hypertensive and normotensive subjects and that the reduced activity in the intact erythrocyte membrane of hypertensive patients is due to an altered membrane environment.     

Purification and characterization of a mammalian myosin I.

Myosin I, an actin-dependent force-generating enzyme, has been purified from three mammalian sources: bovine adrenal medulla, adrenal cortex, and brain. The purification procedure includes extraction of tissue with ATP at low ionic strength and coprecipitation with actin, followed by gel filtration on Sepharose 4B, anion-exchange chromatography on Q Sepharose, and affinity chromatography on ATP-agarose. Mammalian myosin I molecules are composed of a heavy chain of 116 kDa and multiple low molecular weight polypeptides identified as calmodulin. The structural and enzymatic properties of adrenal medulla myosin I were further characterized. This enzyme exhibits high K+,EDTA- and Ca(2+)-ATPase specific activities (about 0.2 mumol.min-1 per mg of protein), whereas the Mg(2+)-ATPase activity is very low (1-3 nmol.min-1.mg-1). The Mg(2+)-ATPase of medulla myosin I is activated by F-actin in a Ca(2+)-dependent manner: activity is stimulated 40-fold in the presence of EGTA and 90-fold in the presence of 10 microM Ca2+. Two structural domains of the myosin I heavy chain were identified. A 74-kDa chymotryptic fragment contains the catalytic site, while a 36-kDa polypeptide contains the calmodulin-binding sites. These results indicate that mammalian myosin I is more closely related to myosin I from the avian intestinal brush border than to the enzymes isolated from the protozoans Acanthamoeba and Dictyostelium.     

(Ca2++Mg2+)-ATPase activity of sickle cell membranes: decreased activation by red blood cell cytoplasmic activator.

Human red blood cells (RBCs) contain a cytoplasmic protein that activates membrane-bound (Ca2+ + Mg2+)-ATPase and the transport of Ca2+. The (Ca2+ + Mg2+)-ATPase of sickle cells showed a less than normal response to this activator. This was true whether the activator was obtained from normal or sickle cells. Activator present in sickle cell hemolysates fully activated the (Ca2+ + Mg2+)-ATPase of normal RBC membranes. These results demonstrate that membranes of sickle cells are defective in their response to the activator. Neither the apparent affinity for calcium nor the apparent affinity for activator was different comparing the (Ca2+ + Mg2+)-ATPase of sickle and normal membranes. Young, mature, and irreversibly sickled cells were separated by density gradient centrifugation, and membranes were prepared from each of these cell populations. No significant differences in ATPase activities were found based on cell age (density). The (Ca2+ + Mg2+)-ATPase of all populations of sickle cells showed a decreased response to the activator. Thus, it appears unlikely that the decreased response of the (Ca2+ + Mg2+)-ATPase of sickle cells is due to membrane damage caused by repeated sickling during the life-span of the cell. Reduced activation of (Ca2+ + Mg2+)-ATPase by the cytoplasmic activator may account for calcium accumulation in sickle cells.     

Changes in phospholipid fatty acid composition of mouse cardiac organelles after feeding graded amounts of docosahexaenoate in presence of high levels of linoleate. Effect on cardiac ATPase activities

Mice were fed diets containing a constant supply of linoleic acid (18:2n-6, LA) as ethyl ester representing 5% by weight of the total fat (5 wt%), in combination with graded amounts of purified docosahexaenoate (22:6n-3, DHA). Cardiac sarcoplasmic reticulum (SR) and mitochondrial phospholipids (PL) from mice fed the diet without DHA contained higher levels of n-6 long chain polyunsaturated fatty acids (PUFA) (22:4n-6 and 22:5n-6) compared to total PL of liver. In the cardiac mitochondrial PL, the level of LA, DHA, the total content of PUFA and the P/S ratio were significantly higher than in SR. A small increase in dietary DHA from 0 to 0.43 wt% induced a 3.6-fold increase in PL DHA content from both cardiac organelles, with a concurrent reduction of n-6 PUFA. The changes in fatty acid PL composition were much more moderate when dietary DHA level was increased to 0.85 and 3.74 wt%. Feeding the lowest amount of DHA resulted in a 6-fold decrease in the value of n-6/n-3 PUFA ratio and a 3.5-fold decrease in the value of 20 carbon chain/22 carbon chain PUFA ratio. DHA was readily depleted from cardiac PL, and only arachidonic acid was retained in the PL from both organelles, after feeding a fat-deficient diet. Despite these drastic modifications in PL fatty acid composition, the maximum velocity (Vm) of SR Ca2+, Mg2+-ATPase was not affected, which indicates that SR cardiac membrane adapts to changes in fatty acid composition to prevent important modifications of its functional properties. However, the Vm of mitochondrial oligomycin-sensitive ATPase was slightly increased in mice fed the lowest amount of DHA. This might be due to an increase in P/S ratio and/or to a modification of cardiolipin fatty acid composition, since this PL is required for optimum function of this enzyme. It is concluded that DHA is strongly taken up by mouse cardiac PL, even in the presence of high dietary LA levels, but its acylation into PL has only little effect on the cardiac ATPase activities.     

Altered cations and muscle membrane ATPase activity in deoxycorticosterone acetate-salt spontaneously hypertensive rats.

The role of ions and cell membrane function in the pathogenesis of benign and malignant hypertension was investigated in spontaneously hypertensive rats (SHR). Ten-week-old male SHR (n = 50) and SHR treated with deoxycorticosterone acetate (DOCA; n = 70) and 1% NaCl drinking water were studied weekly for 14 weeks. Malignant hypertension developed only in DOCA-salt SHR and was characterised by severe hypertension, failure to thrive and renal fibrinoid necrosis. Fourteen DOCA-salt SHR and one SHR died. Extracellular (serum) and intracellular (erythrocyte and muscle) Na+, K+, Mg2+, Ca2+ and muscle membrane Na+,K(+)-adenosine triphosphatase (ATPase), Ca(2+)-ATPase and Mg(2+)-ATPase were measured at various stages in the development of malignant hypertension. Three developmental phases were defined: benign, premalignant and malignant. DOCA-salt SHR showed persistent hypokalaemia. In the benign phase, there were no differences in Na+, Mg2+ and Ca2+ between SHR and DOCA-salt SHR. In the premalignant phase, serum and erythrocyte Mg2+ and ATPase activity were significantly lower in DOCA-salt SHR compared with SHR. During the late premalignant and malignant phases, intracellular Ca2+ and Na+ were significantly higher in the DOCA-salt SHR compared with SHR. In view of these findings, the abnormalities in DOCA-salt SHR during the early phases of blood pressure elevation could be contributory factors to the development of malignant hypertension.     

Physical-chemical and biochemical differences in liver plasma membranes in aging F-344 rats

Age-associated differences in the microviscosity and the activities of enzymes (Mg++-ATPase, Na+,K+-ATPase and 5'-nucleotidase) in the liver plasma membrane were investigated in male and female rats of various ages ranging from 2 to 30 months. The membrane microviscosity, as determined by fluorescence polarization using 1,6-diphenyl-1,3,5,-hexatriene (DPH) as a probe, increased progressively with age after 2 months in male rats, whereas in female rats the microviscosity began to increase only after 24 months. On the other hand, age-associated differences in the activities of membrane-bound enzymes were generally minimal or not significant with the exception of the 5'-nucleotidase activity determined at the pH 9.1, which progressively decreased with age in male rats. The Na+, K+-ATPase activity tended to decrease in both sexes. These decrements in activity did not appear to be large enough, however, to be of definitive physiological significance. These results suggest that age may change the physical-chemical and biochemical qualities of the rat's hepatocyte plasma membrane, but the relationship between the membrane microviscosity and the activities of membrane bound enzymes is not a simple parallelism.     

衰竭心肌能量代谢重构及β3肾上腺素能受体、过氧化物酶体增殖物激活受体α表达变化的研究

目的 通过检测衰竭与健康心肌组织代谢底物含量、相关酶活性及β3肾上腺素能受体、过氧化物酶体增殖物激活受体α（PPARα）基因和蛋白表达的变化,探讨衰竭心肌代谢重构的表现及可能机制。方法 选取6例意外伤亡健康者心肌组织和20例心外科瓣膜置换术的心力衰竭患者,检测心肌游离脂肪酸（FFA）、乳酸（LD）含量和ATP酶活力。应用逆转录聚合酶链反应、Western blot和免疫组化法分别检测心肌组织β3受体和PPARα mRNA表达以及蛋白和定位。结果 衰竭心肌FFA和LD含量明显增加（P〈0．01和P〈0．05）。Na^＋K^＋-ATP酶和Ca^2＋Mg^2＋-ATP酶活性则显著降低（P〈0．05和P〈0．01）。衰竭心肌β3肾上腺素能受体mRNA和蛋白表达明显高于正常心肌,而PPARα表达则显著低于正常心肌,但并未发生定位变化。结论心力衰竭时存在代谢重构,表现为心肌代谢底物发生转变,代谢相关酶活性下降等,β3肾上腺素能受体和PPARα在衰竭心肌分别上调和下调,可能参与心肌组织代谢重构。     

Endoxin Antagonist Lessens Myocardial Ischemia Reperfusion Injury

OBJECTIVE: To elucidate whether endoxin is one of important factors involved in myocardial ischemia reperfusion (MIR) injury, the change of myocardial endoxin level was determined in rats with MIR injury model and the effects of anti-digoxin antiserum (ADA), an endoxin specific antagonist, on MIR injury were studied. METHODS: MIR injury model was obtained by ligating left anterior descending coronary artery 30 min followed by 45 min reperfusion. Sprague-Dawley rats were randomly divided into six groups of 10 rats, each. Sham group, MIR group, normal saline group, ADA 9, 18 and 36 mg.kg(-1). ECG was continuously recorded. After reperfusion left ventricular myocardium samples of ischemic area were processed immediately. Myocardial endoxin level, Na(+)-K(+)-ATPase, Ca(2+)-ATPase, Mg(2+)-ATPase activities, and intramitochondrial Ca(2+) content were measured. RESULTS: Myocardial endoxin level was significantly increased; Na(+)-K(+)-ATPase, Ca(2+)-ATPase, and Mg(2+)-ATPase activities were remarkably decreased; intramitochondrial Ca(2+) content was remarkably raised; ST segments of ECG were significantly elevated and occurrence and scores of ventricular arrhythmias were significantly increased in early stage of reperfusion in rats with MIR. In all groups with ADA, myocardial endoxin level was remarkably decreased; Na(+)-K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase activities were drastically increased; intramitochondrial Ca(2+) content was declined; ST segments and ventricular arrhythmias were improved. CONCLUSION: Myocardial endoxin level was increased in MIR, which implies that the elevated endoxin may be one of major factors inducing MIR injury. This postulate is supported by the observation that ADA has protective and therapeutic effects against MIR injury probably by antagonizing the action of endoxin. The underlying mechanism may be ascribed to restoration of energy metabolism, and attenuation of intracellular Ca(2+) overload.     

Ca2+-transport ATPases of vascular smooth muscle

To characterize the Ca2+-transport properties of the plasma membrane and of the endoplasmic reticulum of bovine pulmonary artery, membrane vesicles are subfractionated by a procedure of density-gradient centrifugation that takes advantage of the selective effect of digitonin on the density of plasma-membrane vesicles. The obtained endoplasmic-reticulum fraction contains hardly any plasma-membrane vesicles, whereas the plasma-membrane fraction is still contaminated by a substantial amount of endoplasmic-reticulum vesicles. An adenosine 5'-triphosphate (ATP) energized Ca2+-transport system and a Ca2+-stimulated ATPase activity are present in both subcellular fractions. The Ca2+ transport by the plasma membrane is catalyzed by a (Ca2+,Mg2+)-ATPase of Mr 130,000. It binds calmodulin and it has a low steady-state phosphoprotein intermediate level. The endoplasmic-reticulum vesicles contain a Ca2+-transport ATPase of Mr 100,000 that is characterized by a high steady-state phosphointermediate level. It is antigenically related to the Ca2+-pump protein of cardiac sarcoplasmic reticulum. Phospholamban, the regulatory protein of the Ca2+-transport enzyme of cardiac sarcoplasmic reticulum, is also present in the endoplasmic reticulum of the pulmonary artery. A comparison of these fractions with the previously characterized fractions from porcine gastric smooth muscle reveals important differences in the basal Mg2-ATPase activity, in the ratio of the (Ca2+,Mg2+)-ATPase of the plasmalemma to that of the endoplasmic reticulum, and in the ratio of the (Na+,K+)-ATPase activity to the plasmalemmal (Ca2+,Mg2+)-ATPase activity. These differences can be ascribed in part to the species and in part to the tissue. These data suggest that in the bovine pulmonary artery the Ca2+ extrusion via the ATP-dependent Ca2+ pump may have a less predominant role, and that the Ca2+ uptake by the endoplasmic reticulum, and possibly also the Ca2+ extrusion via the Na+-Ca2+ exchanger could be more important in this tissue than in the porcine stomach.     

The amino-terminal 200 amino acids of the plasma membrane Na+,K+-ATPase alpha subunit confer ouabain sensitivity on the sarcoplasmic reticulum Ca(2+)-ATPase.

Cardiac glycosides such as G-strophanthin (ouabain) bind to and inhibit the plasma membrane Na+,K(+)-ATPase but not the sarcoplasmic reticulum (SR) Ca(2+)-ATPase, whereas thapsigargin specifically blocks the SR Ca(2+)-ATPase. The chimera [n/c]CC, in which the amino-terminal amino acids Met1 to Asp162 of the SR Ca(2+)-ATPase (SERCA1) were replaced with the corresponding portion of the Na+,K(+)-ATPase alpha 1 subunit (Met1 to Asp200), retained thapsigargin- and Ca(2+)-sensitive ATPase activity, although the activity was lower than that of the wild-type SR Ca(2+)-ATPase. Moreover, this Ca(2+)-sensitive ATPase activity was inhibited by ouabain. The chimera NCC, in which Met1-Gly354 of the SR Ca(2+)-ATPase were replaced with the corresponding portion of the Na+,K(+)-ATPase, lost the thapsigargin-sensitive Ca(2+)-ATPase activity seen in CCC and [n/c]CC. [3H]Ouabain binding to [n/c]CC and NCC demonstrated that the affinity for this inhibitor seen in the wild-type chicken Na+,K(+)-ATPase was restored in these chimeric molecules. Thus, the ouabain-binding domains are distinct from the thapsigargin sites; ouabain binds to the amino-terminal portion (Met1 to Asp200) of the Na+,K(+)-ATPase alpha 1 subunit, whereas thapsigargin interacts with the regions after Asp162 of the Ca(2+)-ATPase. Moreover, the amino-terminal 200 amino acids of the Na+,K(+)-ATPase alpha 1 subunit are sufficient to exert ouabain-dependent inhibition even after incorporation into the corresponding portion of the Ca(2+)-ATPase, and the segment Ile163 to Gly354 of the SR Ca(2+)-ATPase is critical for thapsigargin- and Ca(2+)-sensitive ATPase activity.     

Characterization of membrane fraction lipid composition and function of cirrhotic rat liver. Role of S-adenosyl-L-methionine.

The effect of S-adenosyl-L-methionine (SAM) administration on the lipid composition of the membrane fraction obtained from livers of cirrhotic rats was studied. Four groups of animals were used: group 1 received CCl4 for 8 weeks to induce cirrhosis. Animals in group 2 received 3 daily i.m. injections of SAM 20 mg/kg in addition to CCl4. Groups 3 and 4 were control groups of SAM and vehicles. Seventy-two h after the end of treatment all animals were killed and livers were studied to measure glycogen, cAMP contents and to isolate membrane fractions. The membrane activity of Na+,K(+)- and Ca(2+)-ATPases was measured and the lipid content was analyzed in extracts. Phospholipids were determined by thin-layer chromatography and fatty acids by gas chromatography. Chronic CCl4 treatment led to increases in cholesterol and in the cholesterol/phospholipid ratio. Analysis of phospholipids revealed an increase in phosphatidylserines. Saturated fatty acids increased, while unsaturated decreased significantly. The CCl4-treated group showed a decrease in glycogen and an increase in cAMP contents. Na+,K(+)- and Ca(2+)-ATPases activity were highly reduced in cirrhotic membranes. In the group receiving CCl4 + SAM the lipid composition and the function of liver membrane fraction showed no difference compared to normal controls, except for fatty acid composition which was similar to concentrations in the CCl4-treated group. Glycogen depletion was only partially prevented whereas cAMP levels were normalized in the CCl4 + SAM group. Our results showed that membrane lipid alterations were accompanied by changes in the activity of enzymes embedded in the membrane fraction derived from CCl4-cirrhotic rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fatty acid composition of serum lipids and erythrocyte membranes in type 2 (non-insulin-dependent) diabetic men

The fatty acid (FA) composition of serum lipids and erythrocytes was studied in 21 men with non-insulin-dependent diabetes mellitus (NIDDM) and in 14 normal subjects matched for age, sex, body weight, and dietary intake. Lower levels of linoleic acid and higher levels of highly unsaturated FA (daughter) of n-3 and n-6 family FA, reflected in a higher unsaturation index, were found in serum phospholipids (S-PL), in phospholipids of erythrocyte membranes (ery-PL), and in serum cholesterolesters (S-CHE). The unsaturation index of serum phospholipids significantly correlated with glycosylated hemoglobin A1c (P less than .05) and blood glucose levels after glucose load (P less than .001). The results suggest that elongation and desaturation of essential FA (linoleic acid in particular) are increased. The above changes may be associated with accelerated atherosclerosis in type 2 diabetics.     

The effect of thyroxine on (Na+, K+)-ATPase from the heart and the kidney of rabbit.

The effect of thyroxine on membrane bound (Na+, K+)-ATPase isolated as a microsomal fraction from rabbit heart and kidney was investigated. In the heart, thyroxine administration produced an increased Ki value (a concentration of ouabain required for half maximal inhibition of (Na+, K+)-ATPase activity) without alteration of the specific activity of cardiac (Na+, K+)-ATPase, indicating that the digitalis sensitivity of cardiac (Na+, K+)-ATPase was decreased. On the contrary, a significant increase of the specific activity of renal (Na+, K+)-ATPase was observed without change in its digitalis sensitivity. These results suggest that (1) a decreased sensitivity of cardiac (Na+, K+)-ATPase to digitalis glycosides in thyrotoxic animals may contribute to the decrease in the inotropic and toxic effects of the digitalis glycosides in the hyperthyroid state, and that (2) there may be an organ difference in (Na+, K+)-ATPase.     

Erythrocyte membrane lipids and cationic transport systems in men.

OBJECTIVE: The relationship between erythrocyte membrane and plasma lipids and various transmembrane erythrocyte cationic fluxes was examined in 53 normal men. DESIGN: Different measurements of erythrocyte transport systems were obtained: Na(+)-Li+ countertransport activity; Na+, K+ cotransport activity; Na+, K(+)-ATPase pump activity and the ground membrane permeability for Na+ and K+ as well as the intra-erythrocyte Na+, K+ and Mg2+ concentrations. Plasma cholesterol, triglycerides, phospholipids, free fatty acids, low- and high-density lipoprotein cholesterol levels and the erythrocyte membrane contents of cholesterol, phospholipids and free fatty acids were obtained from fasting subjects. RESULTS: In single regression analysis the erythrocyte Na(+)-Li+ countertransport and Na+, K+ cotransport activities were negatively related to the erythrocyte membrane cholesterol, phospholipids and free fatty acids contents. The Na+, K(+)-ATPase pump activity as assessed by the ouabain-sensitive Na+ efflux was also inversely related to the membrane cholesterol and phospholipids contents. In multiple regression analysis the red blood cell Na(+)-Li+ countertransport activity was independently and negatively related to the membrane cholesterol and free fatty acids contents. CONCLUSION: Our data show that an elevated level of erythrocyte membrane lipids in normal men is accompanied by lower Na(+)-Li+ countertransport, Na+, K+ cotransport and Na+, K(+)-ATPase pump activities.     

Growth hormone and liver mitochondria: time course of effects on respiration and fatty acid composition in hypophysectomized rats

The time course of the effects of GH on state 3 respiration and fatty acid composition of liver mitochondria was investigated up to 48 h after an injection of bovine GH to hypophysectomized rats. The respiratory rate increased significantly by 12 h, whereas the docosahexaenoic acid level, the total unsaturation index, and the ratio of arachidonic acid to linoleic acid of total phospholipids increased as early as 4 h after the hormone injection. A linear association was found between the respiratory rate and the three measures of fatty acid composition. It is concluded that the hormonal effects on respiration may be partly mediated through changes in fatty acid composition, which have an additive effect on increased synthesis of proteins and respiratory chain components.     

Modification of the fatty acid composition of rat heart sarcolemma with dietary cod liver oil, corn oil or butter

The effect of dietary cod liver oil, corn oil or butter upon the lipid composition of cardiac sarcolemma and the activity of sarcolemmal Na+, K+ ATPase was examined in male Wistar rats. The cod liver oil diet caused significant changes in the fatty acid composition of the major phospholipids of sarcolemma, phosphatidyl choline and phosphatidyl ethanolamine. In both these phospholipids arachidonic acid, 20:4 (n - 6) was reduced by about 50% compared to rats fed butter or corn oil and was replaced by the (n - 3) fatty acids eicosapentaenoic and docosahexaenoic acids. The corn oil diet caused a significant diminution in the oleic acid content of phosphatidyl choline and elevation of linoleic acid in phosphatidyl ethanolamine. The phospholipid class composition, total phospholipid fatty acid content and cholesterol content of sarcolemma were not altered by the diets used. The activity of Na+, K+ ATPase in the cardiac sarcolemma was not significantly changed by the different diets.