Effect of ethanol on phospholipid turnover and calcium mobilization in chick embryos

Effects of ethanol on [3H]inositol and [14C]choline incorporation into phosphatidylinositol (PI) and phosphatidylcholine (PC), free intrasynaptosomal Ca2+ ([Ca2+]i) and synaptosomal 45Ca2+ uptake, were investigated in the brain and heart of 17-day-old chick embryos to which a 10% ethanol solution had been injected on the 3rd day of embryogenesis. In brain synaptosomes, ethanol increased the incorporation of [3H]inositol and [14C]choline into PI and PC, increased [Ca2+]i, and decreased 45Ca2+ uptake. On the other hand, in heart synaptosomal membrane, ethanol decreased the incorporation of [3H]inositol and [14C]choline into PI and PC, decreased [Ca2+]i, and increased 45Ca2+ uptake. Ethanol stimulated in vitro [3H]inositol and [14C]choline incorporation into PI and PC in the brain and heart in both the control and ethanol-treated groups. However, addition of ethanol did not affect the release of 45Ca2+ from the synaptosomal membrane of either organ in either group. Addition of ethanol inhibited 45Ca2+ uptake in a dose-dependent manner in the brain but not in the heart. In both organs, there was a relationship between phospholipid turnover and [Ca2+]i after ethanol.     

Effect of ethanol on calcium-uptake and phospholipid turnover by stimulation of adrenoceptors and muscarinic receptors in mouse brain and heart synaptosomes

The effect of ethanol treatment on mouse brain and heart synaptosomal 45Ca uptake and the incorporation of [3H]inositol and [14C]choline into phosphatidylinositol (PI) and phosphatidylcholine (PC) were investigated. Ethanol in drinking water (15%) was given to mice for 3 weeks. The consumption of ethanol increased gradually during treatment but food intake was almost the same as control. The body weight of ethanol-treated mice was slightly less than that of control. The synaptosomal lipid peroxidation level of ethanol-treated mice was almost the same as control in the brain and heart. On the other hand, the synaptosomal glutathione level of ethanol-treated mice was higher than control in both brain and heart. The 45Ca uptake of brain and heart from ethanol-treated mice was 87% and 216% of control mice, respectively. Not only ethanol but also norepinephrine (NE), carbachol (Carb), or isoproterenol (IsoPro) added in vitro increased 45Ca uptake in all cases. The incorporation of [3H]inositol into PI in the brain and heart synaptosomes of ethanol-treated mice was 150% and 113% of control, respectively. The incorporation of [14C]choline into PC in the brain and heart of ethanol-treated mice was 104% and 125% of control, respectively. In vitro addition of ethanol, NE, Carb or IsoPro to brain synaptosomes increased the incorporation of [3H]inositol and [14C]choline into PI and PC, respectively, in both control and ethanol-treated mice. In the case of heart synaptosomes, NE and Carb increased the incorporation of [3H]inositol and [14C]choline into phospholipids in control mice but not ethanol-treated mice. However, IsoPro increased the incorporation by both control and ethanol-treated heart synaptosomes. These results suggest that alpha-adrenoceptors and the cholinergic system of the heart play important roles in modulating the toxic effects of ethanol.     

Effects of dl-propranolol on the synthesis of glycerolipids by rabbit iris muscle

Propranolol (0.03?0.3 mM), an amphiphilic cationic drug which is used therapeutically as a β-blocker, was found to alter significantly the incorporation of [¹⁴C]glucose, [¹⁴C]glycerol, [¹⁴C]acetate, ³²Pi, [³H]cytidine, [³H]inositol, [¹⁴C]choline, [¹⁴C]ethanolamine and [¹⁴C]serine into phospholipids of the iris muscle. Furthermore, it was found to exert a stimulatory effect on the [¹⁴C]serine incorporation into phosphatidylserine of the muscle and microsomes. In contrast, sotalol, another β-blocker-but lacking the hydrophobicity of propranolol-exerted no effect on lipid metabolism. Whereas norepinephrine stimulated only the turnover of the phosphate moiety of phosphatidic acid and phosphatidylinositol, in general propranolol caused the following changes: (a) it stimulated by 2- to 6-fold the labelling of phosphatidic acid and phosphatidylinositol from [¹⁴C]glucose, [¹⁴C]glycerol, [¹⁴C]acetate, ³²Pi and [³H]inositol, (b) it increased by 5- and 38-fold the incorporation of ³²Pi and [³H]cytidine, respectively into CDP-diglyceride, (c) it inhibited appreciably the incorporation of [¹⁴C]glucose, [¹⁴C]glycerol, [¹⁴C]acetate and ³²Pi into phosphatidylcholine and phosphatidylethanoalmine. However, while it inhibited significantly the [¹⁴C]choline incorporation into the former, it stimulated by 60 per cent the ethanolamine incorporation into the latter phospholipid. These results indicate that propranolol probably redirects phospholipid synthesis de novo, by inhibiting phosphatidate phosphohydrolase, such that the increase obtained in the biosynthesis of phosphatidylinositol is accompanied by a corresponding decrease in the synthesis of phosphatidylcholine and phosphatidylethanolamine.Propranolol also caused a 250 per cent increase in the [¹⁴C]serine incorporation into phosphatidylserine of the iris muscle and 28 per cent increase in that of microsomes. The drug appears to stimulate the Ca²⁺ -uptake by muscle and microsomes, which in turn could act to stimulate the Ca²⁺-catalyzed base-exchange reaction.In addition the metabolic pathways involved in the biosynthesis of the major phospholipids of the iris, a smooth muscle, are reported for the first time. These pathways were found to be essentially similar to those reported for other tissues.     

Aluminum impairs glucose utilization and cholinergic activity in rat brain in vitro

The effects of AlCl3 on the production of 14CO2 from [U-14C]glucose and high affinity choline transport in rat brain synaptosomes, and on carbachol-stimulated hydrolysis of phosphoinositides in cortical slices were studied. In buffer containing either high K+ (50 mM) or low K+ (4.9 mM), 1 mM AlCl3 significantly depressed the synaptosomal production of 14CO2 from [U-14C]glucose to 54% and 44% of control rates, respectively. At a concentration of 0.1 mM, AlCl3 depressed the evolution of 14CO2 from [U-14C]glucose from synaptosomes incubated in the high K+ buffer, but did not significantly change 14CO2 production from synaptosomes in the low K+ buffer. Aluminum chloride also inhibited high affinity choline transport in synaptosomes prepared from rat cortex and from hippocampus with an IC50 of approximately 0.5 mM. In brain slices the carbachol-stimulated hydrolysis of phosphoinositides was inhibited by AlCl3 in a dose-dependent manner. One millimolar, 0.5 mM and 0.1 mM AlCl3 inhibited the carbachol-stimulated release of inositol phosphates by 75%, 44% and 33%, respectively. These same concentrations of AlCl3 inhibited the incorporation of [3H]inositol into phospholipids. This inhibitory effect was not dose-dependent as all 3 concentrations of AlCl3 inhibited phospholipid labelling to the same extent (27-37%). These results are discussed in relation to the in vivo neurotoxicity of aluminum.     

Altered lipid metabolism in 2,5-hexanedione-induced testicular atrophy and peripheral neuropathy in the rat

2,5-Hexanedione (HD) induces testicular atrophy and peripheral neuropathy in rats. Since altered lipid metabolism is frequently associated with these disease states, lipid metabolism was investigated in vitro in testes and sciatic nerves of rats fed 1% HD in the drinking water for 6 weeks. Testes from HD-treated rats were 30–60% smaller and weighed threefold less than testes from pair-fed control (PFC) rats. Compared to testes from PFC rats, testes from HD rats exhibited increased incorporation of [¹⁴C]acetate into phospholipids (344%), triacylglycerols (281%), and cholesteryl esters + hydrocarbons (246%) but decreased incorporation into free fatty acids (25%) and sterols + diacylglycerols (65%). The increased incorporation of [¹⁴C]acetate into phospholipids induced by HD reflected an approximate 300% increase into phosphatidyl choline, lysophosphatidyl choline, phosphatidyl serine + phosphatidyl inositol, and phosphatidyl ethanolamine and a disproportionate 800% increase into sphingomyelin. HD rats exhibited clinical signs of peripheral neuropathy, including everted and flat foot placement and hindlimb weakness; similar changes were not observed in PFC rats. In sciatic nerves, the incorporation of [¹⁴C]leucine was decreased into sterols + diacylglycerols (47%), digitoninprecipitable sterols (45%), and cholesteryl esters + hydrocarbons (40%) in HD compared to PFC rats; incorporation of [¹⁴C]leucine into free fatty acids, triacylglycerols, and phospholipids was similar in HD and PFC rats. In contrast to the testis and nerve, lipid metabolism in the liver was similar in HD and PFC rats. The concentrations of 2,5-hexanedione and 2,5-dimethylfuran, respectively, were 0.6 ± 0.3 and 6.5 ± 0.9 μg/g wet weight in the testes and 3.1 ± 0.4 and 3.0 ± 0.4 μg/g wet weight in the livers of HD rats. The data indicate that altered metabolism is associated with HD-induced testicular atrophy and distal axonopathy.     

Modifications of phospholipid metabolism induced by chlorpromazine, desmethylimipramine and propranolol in C6 glioma cells

The effects of chlorpromazine (CPZ), desmethylimipramine (DMI) and propranolol (PRO) on phospholipid metabolism in C6 glioma cells were studied by following the incorporation of 32Pi, [U-14C]glycerol, [2-3H]glycerol and [1-14C]oleate into lipids. The drugs produced a dose-dependent increase in the incorporation of 32Pi and [U-14C]glycerol, but not of [1-14C] oleate, into total phospholipids, that reached a plateau at 200 microM CPZ and 500 microM DMI and PRO. The three drugs shifted the incorporation of precursors from neutral [phosphatidylcholine (PC) and phosphatidylethanolamine (PE)] to acidic phospholipids [phosphatidic acid (PA), phosphatidylinositol (PI), phosphatidylglycerol, phosphatidylinositol-4-phosphate (PIP) and phosphatidylinositol-4,5-bisphosphate (PIP2)] in a dose-dependent, qualitatively similar manner. The incorporation of [2-3H]glycerol into diacylglycerol was also depressed markedly by CPZ. Addition of 1 mM 1,2-dioleoylglycerol, 1-oleoyl-2-acetylglycerol or oleate only partially reversed the decrease in PC labeling caused by CPZ. 12-O-Tetradecanoylphorbol-13-acetate counteracted this effect of CPZ completely but greatly increased PC labeling even in the absence of the drug. Polyphosphoinositides rapidly incorporated 32Pi at early times reaching a plateau in about 40 min. The labeling rate of PI was not parallel to that of PIP or PIP2 and continued to increase even after the polyphosphoinositides had reached a plateau. CPZ increased PI labeling much more than that of PIP and PIP2. These data suggest that cationic amphiphilic drugs may act by inhibiting CTP:phosphocholine cytidylyltransferase, thus decreasing incorporation of precursors into PC and PE; inhibiting PA phosphohydrolase with increased formation of phosphatidyl-CMP, the intermediate for the synthesis of acidic phospholipids; and stimulating the inositol exchange reaction, forming a pool of PI that is not available for PIP and PIP2 synthesis.     

Inhibition of sterologenesis but not glycolysis in 2,5-hexanedione-induced distal axonopathy in the rat

If glycolysis is inhibited in distal axonopathy, there should be a concomitant inhibition of lipogenesis from glucose. To investigate this possibility, lipogenesis from [¹⁴C]glucose and [³H]acetate was studied in sciatic nerves incubated with iodoacetate, a known inhibitor of glycolysis, in sciatic nerves incubated with 2,5-hexanedione, a putative inhibitor of glycolysis, and in sciatic nerves from rats exhibiting clinical signs of peripheral neuropathy induced by 2,5-hexanedione. Nerves incubated with 1.0 mm iodoacetate, in comparison with untreated nerves, exhibited decreased incorporation of [¹⁴C]glucose into sterols + diacylglycerols (33-fold), free fatty acids (14-fold), triacylglycerols (27-fold), and phospholipids (21-fold). In addition, these nerves exhibited decreased incorporation of [³H]acetate into sterols + diacylglycerols (30-fold), free fatty acids (2-fold), triacylglycerols (23-fold), and phospholipids (12-fold). In contrast, the incorporation of [¹⁴C]glucose into sterols + diacylglycerols, free fatty acids, and triacylglycerols was not affected by 1.0 mm 2,5-hexanedione. Compared to untreated nerves, nerves incubated with 1.0 mm 2,5-hexanedione exhibited a small decrease (15%) in the incorporation of [¹⁴C]glucose into phospholipids. Nerves from rats given 1% 2,5-hexanedione in the drinking water for 6 weeks, in comparison with those from pair-fed control rats, exhibited decreased (45%) incorporation of [¹⁴C]glucose and [³H]acetate into digitonin-precipitable sterols. Nerves from 2,5-hexanedione-treated and pair-fed control rats exhibited similar incorporation of [¹⁴C]glucose and [³C]acetate into free fatty acids, triacylglycerols, and phospholipids. The data indicate that while sterologenesis is inhibited in distal axonopathy, glycolysis is not.     

Effect of polychlorinated biphenyls (PCBs) administration on phospholipid biosynthesis in rat liver

The effect of PCBs or phenobarbital on the biosynthesis of phospholipids in hepatic endoplasmic reticulum of rats was studied by the intraperitoneal injection of [³²P]orthophosphate, [Me?¹⁴ C]choline or [2?³H]glycerol. Significant increases in liver microsomal phospholipid content after the administration of either PCBs or phenobarbital indicated the actual proliferation of endoplasmic reticulum membranes. The rate of both [³²P] and [¹⁴C] incorporations into microsomal choline-containing phospholipids, such as phosphatidylcholine, sphingomyelin and lysophosphatidylcholine, was reduced to one fifth by PCBs administration compared with control animals. The incorporation of [³²P]orthophosphate into phosphatidylethanolamine or other phospholipid classes was less or not affected, respectively, by PCBs administration. The specific inhibitory effect of PCBs on the incorporation into cholinecontaining phospholipids was not observed when [2?³-H]glycerol was used as a precursor. Phenobarbital administration, however, increased significantly the rate of [³²P] incorporation into liver phospholipids, especially phosphatidylcholine. It is suggested that the increase in microsomal phospholipid content by PCBs administration is not due to the stimulation of synthesis but to the inhibition of the catabolism of membrane phospholipids and that the increase in content caused by phenobarbital is due at least in part, to the stimulation of synthesis. The possible site(s) of PCBs-induced inhibition of phospholipid biosynthesis in rat liver is discussed.     

Ethanol-induced stimulation of phosphoinositide turnover and calcium influx in isolated hepatocytes

Ethanol has been shown to mobilize intracellular calcium in isolated rat hepatocytes by activation of phosphoinositide-specific phospholipase C. However, addition of ethanol to 32P-labeled hepatocytes resulted in a rapid increase in the level of [32P]phosphatidylinositol 4-phosphate over a period of 2 min, concomitant with a small decrease in [32P]phosphatidylinositol 4,5-bisphosphate and an increase in [32P]phosphatidic acid levels. These results indicate that polyphosphatidylinositol metabolism was stimulated by ethanol simultaneously with the activation of phospholipase C. Ethanol also caused a transient increase in the influx of extracellular calcium into quin 2-loaded hepatocytes over a similar period of time. The results demonstrate that ethanol, in common with calcium-mobilizing hormones, directly or indirectly stimulated polyphosphoinositide regeneration and allowed for increased movement of calcium across the hepatocyte plasma membrane.     

Effect of 4-chlorobiphenyl on substrate transport and phospholipid metabolism in mouse L5178Y lymphoma cells

The toxicity of 4-chlorobiphenyl, a constituent of Aroclor 1221, was studied in mouse L5178Y cells, in vitro. 4-Chlorobiphenyl had a varied effect on the uptake of small precursor molecules. Uptake of [³H]l-leucine, [³H]l-serine, [³H]uridine and [³H]thymidine was inhibited, while that of [³H]inositol was stimulated. There was no significant effect on either [¹⁴C]ethanolamine or [¹⁴C]choline uptake. However 4-chlorobiphenyl significantly inhibited incorporation of [¹⁴C]ethanolamine into phosphatidylethanolamine and caused a 2- to 3-fold stimulation in the incorporation of [¹⁴C]choline into phosphatidylcholine. This effect on phosphatidylcholine metabolism depended on the adsorption and continued presence of 4-chlorobiphenyl on the cell plasma membrane. The stimulation of [¹⁴C]choline incorporation was reversed when treated cells were placed in fresh growth medium under conditions where 95 per cent of the 4-chlorobiphenyl was desorbed from the cell surface. The effect of 4-chlorobiphenyl on substrate uptake and phospholipid metabolism appears to depend upon the interaction of the agent with the cell membrane surface.     

Pancreatic islet arachidonic acid turnover and metabolism and insulin release in response to delta-9-tetrahydrocannabinol

Isolated pancreatic islets from the rat secrete insulin in response to glucose or delta-9-tetrahydrocannabinol (THC). THC stimulated the basal release of insulin and also potentiated the secretory response to glucose. The exposure of control or glucose-stimulated islets to THC inhibited the incorporation of [14C]arachidonic acid (AA) into phospholipids. However, in islets prelabeled with [14C]AA, THC enhanced the glucose-induced loss of AA from phospholipids. The enhanced AA release from islet phospholipids in response to glucose and THC was accompanied by increased synthesis of 12-L-[5,6,8,9,11,12,14,15-3H(N)]-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) and prostaglandin E2. The lipoxygenase inhibitor 3-amino-1-(3-trifluoromethylphenyl)-2-pyrazoline hydrochloride (BW755C) inhibited 12-HETE synthesis and insulin release in glucose and THC-challenged islets; nordihydroguaiaretic acid also inhibited insulin release in THC-treated islets. In contrast, the cyclooxygenase inhibitor, indomethacin, stimulated insulin release. In homogenized islet preparations, THC inhibited acyl-CoA acyltransferase, while it stimulated phospholipase A2 activity. The stimulatory effects of THC on islet cell AA hydrolysis from phospholipids, lipoxygenase product formation, and secretion suggests that these biochemical sequelae in cell activation are important modulators of insulin release.     

Modification of intracellular glucose metabolism in human skin fibroblast preincubated with p-chlorophenoxyisobutyrate.

1. The effect of p-chlorophenoxyisobutyrate (CPIB) on glucose metabolism human skin fibroblasts was examined. 2. CPIB increased the incorporation of 2-deoxy-D-[U-14C]glucose into skin fibroblasts. 3. CPIB decreased [14C]CO2 production from D-[U-14C]glucose but did not affect pyruvate dehydrogenase activity. 4. CPIB reduced fatty acid oxidation activity and cholesterol synthesis but increased triglyceride synthesis. 5. These effects of CPIB were observed both in the presence and in the absence of insulin. 6. One possible mechanism of CPIB on reducing plasma glucose may be due to the increase of glucose incorporation into the cells and triglyceride synthesis in the cells.     

Macrophage-specific effect on lipid metabolism by an antibiotic, ascofuranone

Ascofuranone (AF) enhanced glucose consumption of splenocytes and macrophages, while it enhanced incorporation of [14C]acetate into macrophages but not into splenocytes. When using tumor cell lines, it inhibited the incorporation of [14C]acetate into lymphoma cell lines, YAC-1 and P388, and a thymoma, L5178Y, while it stimulated that into P388D1, which is derived from P388 and has macrophage-like characteristics. Incorporation of [14C]acetate into a mammary carcinoma FM3A was also stimulated by AF. In contrast, AF stimulated uptake of methylglucose in all cell lines tested. The effect of AF was further studied using mouse myeloid leukemia, M1 cells. AF slightly stimulated the incorporation of [14C]acetate into undifferentiated M1 cells, and strongly stimulated that of hydrocortisone-differentiated M1 cells. In contrast, AF suppressed the incorporation of [14C]acetate into retinoic acid-differentiated M1 cells. Glucose consumption of these three types of M1 cells was all stimulated. From these results, we conclude that AF specifically stimulates the incorporation of [14C]acetate into macrophages while it generally stimulates glucose uptake of the cells.     

Effects of chronic ethanol digestion on the fatty acids and phospholipids of spinal cord

The response of spinal cord fatty acids and phospholipids to chronic ethanol ingestion was examined. The distribution as well as concentration of fatty acids was unaltered. The phospholipids were not altered in concentration; however, the composition was altered. Phosphatidyl choline (PC), was increased 43%, while the phosphatidyl serine (PS), plus phosphatidyl inositol (PI) fraction was decreased 26%. These changes may be related to myelin turnover.     

The effect of isoproterenol on the metabolism of phosphatidylinositol by rat heart in vitro

The effect of epinephrine and isoproterenol (10^?4 M) on the incorporation of ³²P orthophosphate and [1-¹⁴C] palmitic acid into rat heart slices was investigated in pulse and chase experiments. Epinephrine stimulated the uptake of ³²P into phosphatidic acid and phosphatidyl-inositol. Isoproterenol stimulated the labelling of phosphatidic acid but had no effect on phosphatidyl-inositol metabolism in the first 60 min of the incubation. Propranolol stimulated the incorporation of ³²P and [1-¹⁴C] palmitic acid into phospholipids in the first 20–30 min of the incubation but counteracted isoproterenol thereafter. These results indicate that the main effect of isoproterenol on phospholipid metabolism in rat heart is to increase the turnover of phosphatidic acid and to slow down the conversion of phosphatidic acid into phosphatidylinositol.     

Effect of artemether on glucose uptake and glycogen content in Schistosoma japonicum.

AIM: To study the effect of artemether (Art) on glucose uptake and glycogen content in schistosomes. METHODS: Schistosomes recovered from mice treated intragastrically with Art 300 mg.kg-1 for 24-48 h, were incubated in the drug-free medium containing [U-14C]glucose 11.1 MBq.L-1. The glycogen content, [U-14C]glucose uptake, and incorporation of [U-14C]glucose into worm glycogen in both male and female worms were determined. RESULTS: When above-mentioned schistosomes were exposed to drug-free medium containing [U-14C]glucose for 1-24 h, the glycogen contents of male and female worms decreased 27%-61% and 39%-78%, respectively. Only 3 out of 6 male worm groups showed 23%-35% decrease in glucose uptake, while much less glucose uptake was found in female worms in all groups with reduction rates of 18%-38%. Apart from 2 male groups no apparent change in the incorporation of [U-14C]glucose into the worm glycogen was seen. CONCLUSIONS: Art-induced glycogen reduction in schistosomes was related to an inhibition of glycolysis rather than an interference with glucose uptake.     

Evidence of differential effects produced by ethanol on specific phospholipid biosynthetic pathways in rat hepatocytes.

1. The aim of the present study was to investigate the effects of ethanol in vitro on the phospholipid biosynthetic pathways in hepatocytes isolated from the rat. We have used [methyl-14C]-choline, [1-3H]-ethanolamine and L-[3-3H]-serine as exogenous precursors of the corresponding phospholipids, phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS). 2. Incubation of hepatocytes in the presence of ethanol significantly alters the incorporation of radiolabel from [14C]-choline and [3H]-ethanolamine into the metabolic intermediates and the final products of the CDP-choline and CDP-ethanolamine pathways. Radioactivity in the metabolic intermediates of both pathways was significantly decreased and the amount of label in PE was reduced whilst that of PC was not modified. 3. In the presence of 4-methylpyrazole, an inhibitor of alcohol dehydrogenase (ADH) activity, ethanol produces a reduction in the label of choline phosphate, ethanolamine phosphate and a significant decrease in the amount of PC and PE radiolabel. 4. On the other hand, ethanol increases the incorporation of serine into phosphatidylserine, phosphatidylethanolamine and phosphatidylcholine, although this effect is observed only in the absence of 4-methylpyrazole, indicating that this alteration is produced by some metabolite generated as a consequence of hepatic alcohol metabolism. 5. Ethanol also interferes with the methylation of phosphatidylethanolamine produced via the CDP-ethanolamine pathway but it does not alter phosphatidylethanolamine methylation when this phospholipid is produced by mitochondrial phosphatidylserine decarboxylation, suggesting the existence of different intramembrane pools of phosphatidylethanolamine, which may exhibit different sensitivity to alcohol. 6. Our results indicate that ethanol exerts two different effects on phospholipid metabolism in hepatocytes: a stimulatory effect on the incorporation of exogenous substrates into different phospholipids probably related to an alteration in the availability of lipogenic substrates as a consequence of ethanol metabolism, and another inhibitory effect produced by ethanol per se, which can be observed only when ethanol metabolism is inhibited by the presence of a specific inhibitor of alcohol dehydrogenase activity.     

Amiodarone-induced phospholipidosis: an in vivo [14C]-acetate uptake study in rat

Amiodarone (AD), a potent antiarrhythmic drug, is often associated with several adverse effects. It is shown to accumulate phospholipids in various tissues, and the impaired catabolism of phospholipids has been implicated in AD-induced phospholipidosis. The synthesis of phospholipids in tissues has not been dealt with. Hence, the incorporation of [14C]-acetate into phospholipids has been studied to understand the AD-induced phospholipidosis in lung and liver. A significant increase in lung and liver phospholipids was observed after 21 and 28 days of AD (175 mg/kg body weight/day) treatment. In the lung and liver, the incorporation of [14C]-acetate into all phospholipid fractions was elevated, while in the lung mitochondria phosphatidylcholine, phosphatidyl ethanolamine and the cardiolipin levels were significantly increased. The results indicate that, in addition to the impaired catabolism of phospholipid, AD treatment resulted in increased phospholipid synthesis.     

Resistance of HepG2 cells against the adverse effects of ethanol related to neutral lipid and phospholipid metabolism

The influence of both short- and long-term ethanol exposure on the lipid metabolism was determined in the human hepatoma cell line HepG2. Ethanol did not cause any cytotoxicity or lipid peroxidation even after 7 days of 100 mM ethanol treatment of HepG2 cells. Incubation of cells in the presence of [1-(14)C]ethanol demonstrated that these cells actively metabolize ethanol to acetyl CoA, incorporating the radioactive label into neutral lipids and phospholipids. [1,2,3-(3)H]glycerol was efficiently used in phospholipid and neutral lipid biosynthesis, showing higher radioactivity in phosphatidylcholine, phosphatidylethanolamine and triacylglycerols. Exposure of HepG2 cells to 100 mM ethanol for 24 hr did not significantly modify the incorporation of glycerol into newly synthesized phospholipids and neutral lipids, nor was lipid degradation affected by the presence of ethanol. When the alcohol treatment was prolonged for 7 days, incorporation of [1,2,3-(3)H]glycerol into triacylglycerols and diacylglycerols showed a slight increase concomitantly with decreased radioactivity in the major phospholipids, phosphatidylcholine and phosphatidylethanolamine. In addition, these changes were associated with a greater release of radiolabeled triacylglycerols into the culture medium. These results indicate that ethanol does not cause in HepG2 cells the marked lipogenic stimulation widely shown in hepatocytes, and demonstrate that HepG2 cells strongly resist the adverse effects of ethanol. Since these cells lack the isoenzymatic form of cytochrome P(450) mainly involved in the ethanol metabolism (namely cytochrome P(450)2E1) and also are devoid of alcohol dehydrogenase activity, we propose that the toxic actions of ethanol on liver must be linked to the activity of one or both of these systems.     

Effects of various antihypertensive agents on lipid metabolism: alterations in the pattern of lipids synthesized from [14C]oleate in rat liver in vitro

The effects of five antihypertensive agents on lipid biosynthesis from [1-14C]oleate were studied in rat liver minces. At a level of 1 mM, propranolol and prazosin increased the incorporation of [14C]oleate into diglycerides and cholesteryl esters by two- to fourfold and increased total phospholipid labeling by 20-30%. Chlorthalidone and metoprolol at 1 mM also stimulated the incorporation of [14C]oleate into phospholipids and diglycerides (20-50%) but did not affect its incorporation into triglycerides or cholesteryl esters. All four of the compounds statistically significantly inhibited the incorporation of [14C]oleate into phosphatidylcholine by 12-37% but stimulated incorporation into phosphatidylinositol by 17-95%. Nadolol differed from the other compounds in that it did not show selective effects but rather inhibited the incorporation of [14C]oleate into all lipid classes by approximately 50%. The data are discussed in terms of possible mechanisms involved in the lipid synthesis patterns and suggest the possibility that plasma lipid/lipoprotein changes observed in patients undergoing antihypertensive therapy may reflect, in part, altered hepatic lipid synthesis.