Effect of ubiquinone on phospholipid metabolism in radiation injury

The synthesis and phospholipid content in the liver, intestine and spleen in normal and irradiated rats administered ubiquinone-9 were studied with the use of 3H-serine. Ubiquinone markedly activated decarboxylation of phosphatidylserine and suppressed transformation of phosphatidylethanolamine to phosphatidylcholine in rat liver and spleen. The effect was also observed in the organs of irradiated animals. In rat intestine, administration of ubiquinone normalized a sharp gamma-irradiation-induced inhibition of transformation of phosphatidylcholine from phosphatidylethanolamine. The catabolism of phospholipids under the action of ubiquinone and radiation was inhibited in the liver and, on the contrary, was activated in radiosensitive organs.     

Actions of dietary orotic acid on liver synthesis of phosphatidylcholine and phosphatidylethanolamine in rats

The in vivo rates of the reactions of the cytidine pathways of liver phosphatidylcholine and phosphatidylethanolamine synthesis were measured in rats after 1 day of feeding on a semisynthetic diet containing 1% orotic acid. The calculations were made from the specific and total radioactivity versus time curves of the precursors and products following intraportal injection of [1,2-14C]choline, [2-14C]ethanolamine, and [2-3H]glycerol. The liver CTP level was increased twofold and the rates of CDP-choline and phosphatidylcholine synthesis were stimulated 4.5-fold in the rats fed orotic acid. The rate of CDP-ethanolamine synthesis was increased but could not be accurately quantified because of its extreme rapidity. No change occurred in the rate of the ethanolaminephosphotransferase reaction and the overall rate of phosphatidylethanolamine synthesis was unchanged by orotic acid feeding. The catalytic activities of the enzymes of the cytidine pathways of phosphatidylcholine and phosphatidylethanolamine synthesis were not affected by feeding orotic acid for 1 day. Similar findings were obtained 3 h following intragastric administration of 100 mg of orotic acid. The results suggest the possibility that changes in the levels of liver CTP may play a role in regulation of the cytidine pathway of liver phosphatidylcholine synthesis but not of phosphatidylethanolamine synthesis, because the latter pathway appears to be tightly controlled at the ethanolaminephosphotransferase step.     

Ca2+-induced phase separation in phosphatidylserine, phosphatidylethanolamine and phosphatidylcholine mixed membranes

Ca2+-induced phase separation in phosphatidylserine/phosphatidylethanolamine and phosphatidylserine/phosphatidylethanolamine/phosphatidylcholine model membranes was studied using spin-labeled phosphatidylethanolamine and phosphatidylcholine and compared with that in phosphatidylserine/phosphatidylcholine model membranes studied previously. The phosphatidylethanolamine-containing membranes behaved in qualitatively the same way as did phosphatidylserine/phosphatidylcholine model membranes. There were some quantitative differences between them. The degree of phase separation was higher in the phosphatidylethanolamine-containing membranes. For example, the degree of phase separation in phosphatidylserine/phosphatidylethanolamine membranes containing various mole fractions of phosphatidylserine was 94--100% at 23 degrees C and 84--88% at 40 degrees C, while the corresponding value for phosphatidylserine/phosphatidylcholine membranes was 74--85% at 23 degrees C and 61--79% at 40 degrees C. Ca2+ concentration required for the phase separation was lower for phosphatidylserine/phosphatidylethanolamine than that for phosphatidylserine/phosphatidylcholine membranes; concentration to cause a half-maximal phase separation was 1.4 . 10(-7) M for phosphatidylserine-phosphatidylethanolamine and 1.2 . 10(-6) M for phosphatidylserine/phosphatidylcholine membranes. The phase diagram of phosphatidylserine/phosphatidylethanolamine membranes in the presence of Ca2+ was also qualitatively the same as that of phosphatidylserine/phosphatidylcholine except for the different phase transition temperatures of phosphatidylethanolamine (17 degrees C) and phosphatidylcholine (-15 degrees C). These differences were explained in terms of a greater tendency for phosphatidylethanolamine, compared to phosphatidylcholine, to form its own fluid phase separated from the Ca2+-chelated solid-phase phosphatidylserine domain.     

Effect of thyroid dysfunction upon phospholipid composition and CDP-choline incorporation in mitochondria and microsomal fraction isolated from liver and brain of suckling rats

The phospholipid composition and the in vitro incorporation of radioactive CDP-choline into phosphatidylcholine was studied in mitochondria and microsomal fraction obtained from liver and brain of 20 day old hyperthyroid or hypothyroid rats. The chemical composition of the subcellular membranes isolated from brain differed markedly in both conditions. In hyperthyroidism the microsomal fraction was slightly affected while the mitochondria were also affected, but not as severely as in hypothyroidism, in which the microsomal fraction showed no alterations.The incorporation of the radioactive precursor into brain mitochondria isolated from hyperthyroid rats was markedly decreased, while no changes were observed in microsomes. However, incorporation into brain microsomal fraction obtained from hypothyroid rats was increased, while no changes were observed in mitochondria. Similar results were obtained in the studies performed with liver subcellular membranes from hyperthyroid animals while no changes were found in those from hypothyroid rats.Our results indicate that both experimental conditions affect in a different way the structure and function of brain mitochondria and microsomal fractions. They also give further support to our hypothesis that mitochondria have a certain degree of autonomy for the synthesis of phosphatidylcholine.Abbreviations used PS+PI phosphatidylserine+phosphatidylinositol - Sph sphingomyelin - PC phosphatidylcholine - PE phosphatidylethanolamine     

Phospholipid composition of normal and transformed cells cultivated with N-acylethanolamines

Effects of N-stearoylethanolamine (NSE), N-oleoilethanolamine (OEA) and mixture of more than 20 saturated and unsaturated N-acylethanolamines on phospholipids composition of normal and transformed fibroblasts in the culture were compared in the work. It was shown that cultivation of cells NSE decreases percent content of phosphatidylinositol (PI), phosphatidylserine (PS) and sphingomyeline (SM) - important mediators of cell signaling. Under the influence of OEA the level of SM decreases as well, but at the same time PI and PS levels increase. NAEs mixture decreases PS and PI levels in cells and causes phosphatidylcholine (PC) amount increase. Moreover NSE and NAEs mixture decrease the content of main mitochondria membrane lipid - diphosphatidylglicerole (DPG). OEA increases DPG amount. In transformed fibroblasts (line L929) NAE modulate lipid composition as well: NSE decreases the level of phosphatidylethanolamine (PE), OEA and NAEs mixture increase sphingomyeline levels. It is shown that response of normal and transformed fibroblasts on NAE application is different, depending on substance structure and cell-target type.     

Lipids of marine cold-water fishes

The study deals with the lipid and fatty acid compositions of the muscles, gills and liver of marine fishes inhabiting cold waters (0.5–6°C) and caught in Peter the Great Bay (3 species) and Vostok Bay (2 species), as well as with the fatty acid compositions of the main phospholipids in the muscle tissues of fish from Olyutorskii Bay (4 species). The average content of phosphatidylcholine was about 60% in muscles and in the liver and 53.8% of the sum of all phospholipids in gills. The phosphatidylethanolamine content was on the average 24.3, 25.1 and 22.3% in muscles, liver and gills, respectively. Increased contents of phosphatidylserine and sphingomyeline were recorded in the gills. The mean (S.D.) molar ratios of cholesterol/phospholipids were 0.20, 0.32, and 0.58 in the muscles, liver, and gills, respectively. It was established that phosphatidylcholine has a higher content of saturated fatty acids, whereas phosphatidylethanolamine was richer in monoenic acids and docosahexaenoic acid (DHA). It was noted that the level of polyenic fatty acids was increasing and the level of monoenic and saturated acids was decreasing in the series from gills-liver-muscles. The species with a more active mode of life were distinguished by an increased content of docosahexaenoic acid.     

Phospholipid content in "late" posttraumatic epileptic focus in rabbits

The phospholipids content in the cortex, hippocamp and stem tissues in rabbits with "late" posttraumatic epileptic focus (1 year after the light brain injury) was estimated. There was established an increase of the content of phosphatidylethanolamine, sphingomyeline, phosphatidylinosite, phosphatidic acid, non-identified phospholipids, decrease of the content of phosphatidylcholine and cardiolipine and appearance of lysophosphatidylcholine in the cortical epileptic focus tissues. The conclusion is made that the changes within the phospholipids pool may cause the epileptogenic disturbance in the neurons, i.e. the changes of functional properties of the excitable membranes and the activity of the mytochondrial phospholipid-dependent enzyme complex.     

Dietary orotic acid accentuates the hepatic response to phenobarbital in rats.

In rats treated with phenobarbital for 3 days and simultaneously fed a semisynthetic diet containing 1.0% orotic acid, the extent of the increases in liver microsomal phosphatidylcholine, phosphatidylethanolamine, total RNA, total protein, and cytochrome P-450 were significantly greater than they were in rats treated identically with phenobarbital but without dietary orotic acid. This is attributed primarily to the stimulation of hepatic phosphatidylcholine synthesis by dietary orotic acid. In the absence of phenobarbital, orotic acid was shown to cause some increase in liver smooth endoplasmic reticulum components, but not cytochrome P-450. Orotic acid also decreased the activity of microsomal phosphatidylethanolamine N-methyltransferase, which may have contributed to the increase in the microsomal content of phosphatidylethanolamine. The hypothesis is advanced that phospholipid availability is a limiting factor in the hepatic response to phenobarbital. When more phospholipid is available to provide the structural framework for biogenesis of endoplasmic reticulum, all of the hepatic actions of phenobarbital, including induction of cytochrome P-450, are amplified.     

Ca2+-induced phase separation in phosphatidylserine,phosphatidylethanolamine and phosphatidylcholine mixed membranes

Ca²⁺-induced phase separation in phosphatidylserine/phosphatidylethanolamine and phosphatidylserine/phosphatidylethanolamine/phosphatidylcholine model membranes was studied using spin-labeled phosphatidylethanolamine and phosphatidylcholine and compared with that in phosphatidylserine/phosphatidylcholine model membranes studied previously. The phosphatidyl-ethanolamine-containing membranes behaved in qualitatively the same way as did phosphatidylserine/phosphatidylcholine model membranes. There were some quantitative differences between them. The degree of phase separation was higher in the phosphatidylethanolamine-containing membranes. For example, the degree of phase separation in phosphatidylserine/phosphatidylethanolamine membranes containing various mole fractions of phosphatidylserine was 94–100% at 23°C and 84–88% at 40°C, while the corresponding value for phosphatidylserine/phosphatidylcholine membranes was 74–85% at 23°C and 61–79% at 40°C. Ca²⁺ concentration required for the phase separation was lower for phosphatidylserine/phosphatidylethanolamine than that for phosphatidylserine/phosphatidylcholine membranes; concentration to cause a half-maximal phase separation was $\text{1.4 · 10}{}^{\mathrm{?7}}$ M for phosphatidylserine-phosphatidylethanolamine and $\text{1.2 · 10}{}^{\mathrm{?6}}$ M for phosphatidylserine/phosphatidylcholine membranes. The phase diagram of phosphatidylserine/phosphatidylethanolamine membranes in the presence of Ca²⁺ was also qualitatively the same as that of phosphatidylserine/phosphatidylcholine except for the different phase transition temperatures of phosphatidylethanolamine (17°C) and phosphatidylcholine (?15°C). These differences were explained in terms of a greater tendency for phosphatidylethanolamine, compared to phosphatidylcholine, to form its own fluid phase separated from the Ca²⁺-chelated solid-phase phosphatidylserine domain.     

Differences in the Kinetics of Axonal Transport for Individual Lipid Classes in Rat Sciatic Nerve

Lipid precursors ([2-3H]glycerol for phospholipids and [3H]acetate for cholesterol) were injected into the L-5 dorsal root ganglion of adult rats. At various times, animals were killed, the ganglion and consecutive 5-mm segments of sciatic nerve were dissected, and lipids were extracted and analyzed by TLC. Individual lipid classes exhibited markedly different transport patterns. The crest of radioactive phosphatidylcholine moved as a sharply defined front at about 300 mm/day, with a relatively flat plateau behind the moving crest. Although some radioactive phosphatidylethanolamine also moved at the same rate, the crest was continually attenuated as it moved so that a gradient of radioactive phosphatidylethanolamine along the axon was maintained for several days. Transported diphosphatidylglycerol exhibited a defined crest, as did phosphatidylcholine, but moved at about half the rate. Labeled cholesterol was transported at a rapid rate similar to that for phosphatidylcholine and phosphatidylethanolamine, but like phosphatidylethanolamine, the initial moving crest of radioactivity was continually attenuated. Relative to the phospholipids, cholesterol showed a more prolonged period of accumulation in the axons and was more metabolically stable. We propose that most labeled phosphatidylcholine, phosphatidylethanolamine, and cholesterol is transported in similar (or the same) rapidly moving membranous particles. Once incorporated into these particles, molecules of phosphatidylcholine tend to maintain associated with them during transport. In contrast, molecules of phosphatidylethanolamine and cholesterol in these transported particles exchange extensively with unlabeled molecules in stationary axonal structures. Diphosphatidylglycerol, localized in a specialized organelle, the mitochondrion, is transported at a slower rate than other phospholipids, and does not exchange with other structures.     

The N-stearoylethanolamine effect on the NO-synthase way of nitrogen oxide formation and phospholipid composition of erythrocyte membranes in rats with streptozotocine diabetes

The influence of N-stearoylethanolamine (NSE) on the NO-synthase way of NO generation and phospholipids composition of erythrocyte membranes of rats with streptozotocine-induced diabetes has been studied. It has been shown that the activation of iNOS activity, cNOS activity inhibition and increase of the stable NO metabolites content takes place in the red blood cells (RBC) of diabetic rats. The alterations were also found in the RBC membrane phospholipid content: a decrease of phosphatidylethanolamine, phosphatidylcholine, phosphatidylinositol, sphingomieline content and increase of phosphatidylethanolamine, phosphatidylcholine lysoforms level. The NSE suspension administration (50 mg/kg of body weight) to diabetic rats (3 months after the diabetes induction) resulted in iNOS activity inhibition, recovering of cNOS activity and normalization of NO stable metabolites level in RBC. The decrease of phospholipids lysoform levels, normalization of phosphatidylethanolamine, phosphatidylcholine content and increase of phosphatidylinositol level were found after NSE action.     

Estradiol- and testosterone-induced alterations in phosphatidylcholine and triglyceride synthesis in hepatic endoplasmic reticulum

Pathways of phosphatidylcholine and triglyceride biosynthesis were studied in hepatic endoplasmic reticulum from castrated and noncastrated male rats pretreated with estradiol or testosterone. In vitro measurements of hepatic microsomal enzymes which catalyze phosphatidylcholine biosynthesis revealed a significant increase in the specific activity of the enzyme governing phosphatidylcholine biosynthesis by the sequential methylation of phosphatidylethanolamine in the estradiol-treated castrate animals. The specific activity of phosphorylcholine-glyceride transferase was decreased by estradiol treatment in both castrate and noncastrate animals. The specific activity of diglyceride acyltransferase, which catalyzes triglyceride biosynthesis, was decreased by estradiol pretreatment in both castrate and noncastrate animals and was increased by testosterone in the castrate animals. The changes in specific activity of the enzymes governing phosphatidylcholine biosynthesis may account for the previously noted increased in vivo incorporation of methyl groups of l-methionine into hepatic phosphatidylcholine in female and estradiol-treated animals; the data suggest that in female and estradiol-treated rats a greater proportion of hepatic phosphatidylcholine is synthesized by the stepwise methylation of phosphatidylethanolamine. The decrease in diglyceride acyltransferase specific activity seen after estradiol administration may account for the lipotropic-like effect of estradiol.     

Phospholipid and cholesterol levels in the tumor cell plasma membranes with different sensitivity to doxorubicin

The investigation is aimed to study qualitative and quantitative composition of phospholipids, cholesterol content and lipids unsaturation index in plasma membranes of Guerin's carcinoma cells sensitive or resistant to doxorubicin. The comparison of infrared spectra and phospholipids unsaturation index showed that the unsaturation level of fatty acids in plasma membrane from resistant cells was lower than that from sensitive carcinoma cells. 31P-NMR spectroscopy of plasma membranes phospholipids shows the increase of phosphatidylserine and sphingomyeline content in plasma membrane isolated from resistant tumor as compared with sensitive tumor. The levels of phosphatidylcholine and phosphatidylethanolamine were equal in drug-resistant and drug-sensitive carcinoma strains. Changes in plasma membrane from resistant cells result in elevation of plasma membrane microviscosity and phosphatidylserine level increase can suggest the activation of P-glycoprotein-mediated efflux of doxorubicin.     

Phospholipid turnover in soybean tissue cultures

The degradation rates of phospholipids in soybean (Glycine max L. Merrill) suspension cultures were studied by pulse-chase experiments. The only chloroform-soluble product of incorporation of radioactive choline was phosphatidylcholine, the bulk of which had a half-life of 36 hours. Ethanolamine was incorporated primarily into phosphatidylethanolamine, phosphatidylcholine at an intermediate level, and phosphatidylmonomethylethanolamine to a small extent. The phosphatidylethanolamine decayed in a triphasic fashion with half-lives of 12, 34, and 136 hours. Phosphatidylcholine in this case increased in radioactivity up to day 4 and thereafter declined with a 92-hour half-life. The radioactivity rose slightly to day 4 in phosphatidylmonomethylethanolamine after an initial rapid decline. When serine was used as a substrate, half-lives similar to those obtained with ethanolamine were obtained. Phosphatidylcholine contained the greatest amount of label, however, with phosphatidylethanolamine containing slightly less, and phosphatidylserine contained the least. Data also are presented for glycerol and acetate phospholipid product degradation.     

Effect of acute thioacetamide administration on rat brain phospholipid metabolism

Brain phospholipid composition and the [³²P]orthophosphate incorporation into brain phospholipids of control and rats treated for 3 days with thioacetamide were studied. Brain phospholipid content, phosphatidylcholine, phosphatidylethanolamine, lysolecithin and phosphatidic acid did not show any significant change by the effect of thioacetamide. In contrast, thioacetamide induced a significant decrease in the levels of phosphatidylserine, sphingomyelin, phosphatidylinositol and diphosphatidylglycerol. After 75 minutes of intraperitoneal label injection, specific radioactivity of all the above phospholipids with the exception of phosphatidylethanolamine and phosphatidylcholine significantly increased. After 13 hours of isotope administration the specific radioactivity of almost all studied phospholipid classes was elevated, except for phosphatidic acid, the specific radioactivity of which did not change and for diphosphatidylglycerol which showed a decrease in specific radioactivity. These results suggest that under thioacetamide treatment brain phospholipids undergo metabolic transformations that may contribute to the hepatic encephalopathy induced by thioacetamide.     

The apparent transfer of fatty acid from phosphatidylcholine to phosphatidylethanolamine in human erythrocytes

In previous studies an apparent transfer of (14)C-labeled fatty acid from phosphatidylcholine to phosphatidylethanolamine was observed in prelabeled human erythrocytes reincubated in fresh serum. These data could have been explained by direct fatty acid transfer from phosphatidylcholine to phosphatidylethanolamine or by an apparent transfer simulated by either demethylation of labeled phosphatidylcholine to phosphatidylethanolamine or base-exchange of phosphatidylcholine with ethanolamine. To explore these possibilities, RBC containing phosphatidylcholine doubly labeled with palmitic acid-9,10-(3)H and with choline-1,2-(14)C were prepared. Upon reincubation in fresh serum, incorporation of (3)H (fatty acid) into phosphatidylethanolamine was observed without incorporation of (14)C (choline). In similar experiments in which RBC labeled with (3)H-labeled fatty acid alone were used, (14)C-ethanolamine added to the incubation was not incorporated into the isolated phosphatidylethanolamine which again showed incorporation of the fatty acid-(3)H. The data indicate that direct transfer of fatty acid from phosphatidylcholine to phosphatidylethanolamine can occur in human erythrocytes incubated in fresh serum.     

Single-channel parameters of gramicidin A,B, and C.

The single-channel conductance lambda and the mean channel lifetime gamma of natural and synthetic gramicidins A, B, and C has been studied. Significant differences in delta were found between gramicidin A and B; both gramicidins differ only in one amino acid (tryptophan replaced by phenylaline). The distribution of lambda is narrow in glycerylmonooleate membranes but considerably broader in dioleoyl phosphatidylcholine and dioleoyl phosphatidylethanolamine membranes. The ratio of the single-channel conductances in glycerylmonooleate and dioleoyl phosphatidylcholine membranes is only about two and is considerable smaller than the conductance ratio of nonactin-mediated cation transport. This finding suggests that dipolar potentials at the membrane/solution interface have little influence on the conductance of the gramicidin channel.     

Single-channel parameters of gramicidin a,b, and c

The single-channel conductance Λ and the mean channel lifetime τ1 of natural and synthetic gramicidins A, B, and C has been studied. Significant differences in Λ were found between gramicidin A and B; both gramicidins differ only in one amino acid (tryptophan replaced by phenylalinine). The distribution of Λ is narrow in glycerylmonooleate membranes but considerably broader in dioleoyl phosphatidylcholine and dioleoyl phosphatidylethanolamine membranes. The ratio of the single-channel conductances in glycerylmonooleate and dioleoyl phosphatidylcholine membranes is only about two and is considerable smaller than the conductance ratio of nonactin-mediated cation transport. This finding suggests that dipolar potentials at the membrane/solution interface have little influence on the conductance of the gramicidin channel.     

Lipid composition of liver peroxisomes isolated from untreated and clofibrate-treated mice and rats

Peroxisomes were isolated from liver tissue of control and clofibrate-treated adult male NMRI mice and Sprague-Dawley rats. Phospholipids, cholesterol, triglycerides and free fatty acids were measured in the peroxisomes. The fatty acid profiles of the phosphatidylethanolamine, the phosphatidylcholine, the triglyceride and the free fatty acid fractions were also analyzed. Phosphatidylethanolamine was the dominating phospholipid in peroxisomes from untreated animals. The fatty acid profiles of phosphatidylethanolamine, free fatty acids and triglycerides were similar for untreated mice and rats but differences between the species were observed in the pattern derived from phosphatidylcholine. Phosphatidylcholine was the most abundant phospholipid after clofibrate treatment. Clofibrate treatment caused an increase in the concentrations of phospholipids and unsaturated long-chain fatty acids and a decrease in the concentrations of triglycerides, free fatty acids, cholesterol and shorter saturated fatty acids.     

The stereochemical configuration of lysosomal phosphatidylcholine and phosphatidylethanolamine: comparison with lysobisphosphatidic acid.

Lysosomal phosphatidylcholine and phosphatidylethanolamine were isolated from liver of rats treated with Triton WR 1339 and from cultured BHK-cells. Stereochemical analysis proved that these lipids, in contrast to the lysosomal lysobisphosphatidic acid, were derivatives of sn-glycero-3-phosphate.