Effect of Retinol on Liver Lipid Metabolism of Rats

Effect of feeding 4.23, 16.94 and 27.53 mg of retinol daily for 10 days on the liver lipids of adult rats has been studied. Feeding of different amounts of retinol produced dose dependent toxicity symptoms in rats. Retinol feeding resulted in significant elevations of liver total lipids, total fatty acids, and glycerides, The amounts of liver esterified cholesterol were significantly raised in rats fed different amounts of retinol. Acetate-1-¹⁴C incorporation was increased in liver total cholesterol of rats fed 27.53 mg retinol and in free cholesterol of all retinol fed rats. Total ¹⁴C activity of hepatic triglycerides of retinol fed rats was the same as that of control, but their specific activity was decreased. Significant alterations were noted in phosphatidyl serine, lysophosphatidyl choline, lysophosphatidyl ethanolamine, sphingomyelin, phosphatidyl choline, phosphatidyl ethanolamine and phosphatidic acid and polyglycerophosphate fractions in liver rats fed different amounts of retinol.     

Hepatic Subcellular Fractions Lipids in Rats Fed Millet (Sorghum vulgarie) at Different Protein Levels

Effect of feeding defatted millet (Sorghum vulgarie) flour at 5, 10 and 14.5% protein levels respectively for six weeks has been studied on rat liver mitochondrial, microsomal and supernatant fractions total lipids, cholesterol, triglycerides, total phospholipids, phosphatidyl choline and phosphatidyl ethanolamine. The results have been compared with rats fed casein at 10% level for the same period. The metabolism of liver subcellular fractions lipids of millet diet and casein diet fed rats has been studied by the incorporation of acetate-1-¹⁴C and . A significant increase in mitochondrial triglycerides of rats fed millet diet at 5 and 10% protein level, in microsomes of rats fed millet diet at 5, 10 and 15% protein levels and in supernatant fractions of rats fed millet diet at 5 and 15% protein levels was observed. A significant increase in total cholesterol in mitochondria and microsomes and a significant decrease in supernatant fraction of rats fed millet diet at 10% protein level was observed. A significant increase in mitochondrial total phospholipids, phosphatidyl choline and phosphatidyl ethanolamine in rats fed millet diet at 10% protein level and a decrease in these in rats fed millet diet at 5 per cent protein level was observed. In microsomes total phospholipids were increased in rats millet diet at 10% protein level and phosphatidyl choline was increased in rats fed millet diet at 15% protein level. Total phospholipids, phosphatidyl choline and phosphatidyl ethanolamine were significantly reduced in the supernatant fraction of rats fed millet at 10% protein level.

Incorporation of acetate-1-¹⁴C into nonsaponifiable fraction of mitochondria, microsomes and supernatant fractions of rats fed millet diet at 5 and 15 % protein levels was significantly greater, and in saponifiable fractions of the above subcellular fractions was greater in rats fed millet diet at 5 per cent protein level. The specific activity (counts/min/mg) of free cholesterol in mitochondria, microsomes and supernatant fractions of millet diet fed rats was significantly greater, whereas the specific activity of triglycerides was not significantly different from the controls. The acetate-1-¹⁴C specific activity of phosphatidyl choline and phosphatidyl ethanolamine was significantly greater in all the above subcellular fractions of millet diet fed rats (except of phosphatidyl choline in rats fed millet diet at 5 % protein level). The specific activities of phosphatidyl choline were significantly greater in mitochondria of rats fed millet diet at 5 % protein level and of phosphatidyl choline and phosphatidyl ethanolamine in microsomes and supernatant fractions of rats fed millet diet at 5 and 15% protein levels. The specific activities of phosphatidyl choline were significantly decreased in mitochondria and microsomes of rats fed millet diet at 10% protein level. The total acetate-1-¹⁴C activities (counts/min/g equivalent wet liver) of free and esterified cholesterol triglycerides, phosphatidyl choline and phosphatidyl ethanolamine showed that their synthesis from acetate-1-¹⁴C was either enhanced in millet diet fed rats or was comparable to the controls. The total activity of (counts/min/g equivalent wet liver) into phosphatidyl choline and phosphatidyl ethanolamine showed that their synthesis was decreased in microsomes of rats fed millet diet at 10% protein level, increased in rats fed millet diet at 5 and 15% protein levels.     

Effect of Feeding Defatted Millet (Sorghum vulgarie) Flour at Different Protein Levels on Phospholipids of Rat Liver

Effect of feeding defatted millet flour at 5, 10 and 14.5 percent protein levels respectively to rats for 6 weeks has been studied on their liver phospholipids. Feeding of millet at these protein levels significantly increased liver total lipids and total glycerides as compared to control rats fed casein at 10 percent level. Liver phospholipids and phosphatidyl choline were significantly increased in rats fed millet at 10 and 14.5 percent protein levels whereas phosphatidyl ethanolamine was increased in all millet protein fed groups. Incorporation of (counts/liver/100 g body weight) into liver total phospholipids, phosphatidyl choline and phosphatidyl ethanolamine was significantly increased in M–5 and M–15% groups and it was decreased in phosphatidyl choline in rats of M–10% groups as compared to control. The effects of feeding millet on liver phospholipids are due to the quantity as well as quality of the millet protein.     

Phospholipids of rat tissues after feeding pure phosphatidyl ethanolamine and lecithin

Pure phosphatidyl ethanolamine and lecithin from egg yolks were fed to rats in saline or in olive oil and the changes in individual phospholipids in the intestinal wall, liver, and plasma of the animals were studied. Ingestion of olive oil alone produced increased levels of all phospholipid fractions in each of the three tissues. Feeding phosphatidyl ethanolamine in saline resulted in slightly increased plasma phospholipids, but levels of liver total phospholipids were greatly reduced; when phosphatidyl ethanolamine was fed with olive oil, liver phospholipids were again reduced but this reduction was confined to the phosphatidyl ethanolamine and phosphatidic acid fractions. Feeding lecithin alone did not produce significant changes in levels of plasma or tissue phospholipids. The results suggest that liver phospholipid synthesis is depressed by feeding phosphatidyl ethanolamine; in the presence of olive oil, hepatic synthesis of phosphatidyl ethanolamine seems to be more selectively inhibited.     

Effect of Feeding Millet (Sorghum vulgarie) Protein at Various Protein Levels on Adrenal Lipids of Rats

A significant increase in adrenal weight, total lipids, cholesterol phospholipids and glycerides (mono-and triglycerides) was observed in rats fed millet at 5, 10 and 15 % protein levels respectively for a period of six weeks as compared to rats fed casein at 10 per cent level. Increases in cholesterol were in both its free and esterified fraction. Adrenal phosphatidyl etha-nolamine was increased in all millet fed rats whereas phosphatidyl choline increased in M–15 % and decreased in M–5 % groups. Other phospholipid fractions viz. monophosphatidyl inositol, lysophosphatidyl ethanolamine, sphingomyeline, phosphatidic acid and polyglycerophosphatide also showed significant alterations in rats fed millet protein as compared to control. Incorporation of acetate–l–¹⁴C into adrenal lipids was lower and that of glucose–U–¹⁴C, palmitate–l–¹⁴C and NaH₂³²PO₄ was higher than the control.     

Effects of dexamethasone on lipid metabolism in rat organs

Injecting of dexamethasone (10 mg/kg body weight) for 8 days to rats decreased the body weight and feed intake by 29 and 50%, respectively. The increase in weights of liver, heart, kidneys and testes per 100 g body weight was 55, 37, 33 and 13%, respectively. Though, in general, the triglyceride content increased in all the organs, maximum increase (9-fold) was observed in the liver. The plasma showed elevated levels of triglycerides, cholesterol and phospholipids. In hepatic mitochondrial membranes, the content of protein, phospholipids and cholesterol decreased/g tissue. The percent 14C distribution, as a part of total incorporation in nonpolar lipids, of [14C]acetate into triglycerides of liver, kidneys and testes increased significantly. The increased turnover of phospholipids in liver and heart was mainly due to increased turnover of phosphatidyl choline (PC) and phosphatidyl ethanolamine in liver and PC in heart. Turnover of phospholipids of testes was not affected.     

Effect of acute hypobaric hypoxia on 32-P incorporation into phospholipids of alveolar surfactant, lung, liver and plasma of rat.

Exposure of adult rats to hypobaric hypoxia caused hypolipidemia, hypotriglyceridemia and hypophospholipidemia. Hypobaric hypoxia produced an increase in liver triglyceride and cholesterol levels and a decrease in lung triglyceride, total phospholipid and phosphatidyl choline. The proportion of phosphatidyl choline in the pulmonary surfactant fraction I phospholipids (responsible for reducing surface tension) decreased (55.2% as compared to 80.4% in control animals). Incorporation of 32-P into liver phosphatidyl ethanolamine was significantly increased, incorporation into lung phosphatidyl choline and phosphatidyl ethanolamine was increased whereas a decreased incorporation into plasma phosphatidyl choline was observed. The data suggest an enhanced lipid synthesis in liver with a probable impairment of mobilization into plasma.     

Hormonal influence on testicular lipids.

The effects of progesterone and progesterone plus oestrogen (PPO) on testicular lipids of adult rats were studied. Treatment with progesterone over 7 days did not alter significantly the total lipids, cholesterol, glycerides and phospholipids. However, PPO administration brought about a significant elevation in total lipids, mainly contributed by the increase in triglycerides. The phospholipids and total cholesterol were not markedly affected by PPO treatment, but the individual classes of phospholipids showed marked alterations in their pattern of distribution. The esterified and free cholesterol fractions were found to be significantly altered by both the treatments. Progesterone appears to favour ester cholesterol accumulation by depleting the available free cholesterol. Oestrogen seems to increase the glycerides and change the concentration of phosphatidyl serine, phosphatidyl choline and phosphatidyl ethanolamine when administered with progesterone.     

Die Lipide von Endomycopsis vernalis bei verschiedener Stickstoff-Ernährung

1. Endomycopsis vernalis was cultivated on media with different N supply: series A 1%, series B 0,125% asparagine. Sonified cells were extracted and yielded 14.3% (A) and 65.3 (B) total lipids/non lipid dry matter respectively.
2. Neutral and complex lipids were separated by rubber membrane dialysis. There is no difference in the percentage of complex lipids of both series. The increase of lipids in cells grown on low N level is due to a higher content of neutral lipids.
3. Components of the neutral lipids, analysed by DC, were diglycerides, triglycerides, free and esterified ergosterol. Their percentage is influenced by the nutritional conditions. There is a significant increase of triglycerides and of sterol esters in the high lipid cells of series B.
4. Methyl esters of component fatty acids of glycerides and sterol esters were analyzed by GLC. Saturated acids C₁₄, C₁₅, C₁₆, C₁₇, C₁₈, monoenic acids C₁₆ and C₁₈, linoleic and linolenic acids were found to be present. Major acids were in all cases 18:1 (17–57%), 18:2 (18–50%) and 16:0 (10–18%). Linolenic acid is higher in di-and triglycerides of low lipid cells of series A than in high lipid cells of series B. Both qualitative and quantitative differences of fatty acids were found in sterol esters of series A and B respectively.
5. The major components of complex lipids, identified by DC and isolated by CC, in both series, were phosphatidyl choline (A:36.5, B:41.0%) and phosphatidyl ethanolamine (A:24.9, B:20.5%) in addition to small amounts of lysophosphatidyl choline, lysophosphatidyl ethanolamine, phosphatidyl serine, monophosphoinositide, diphosphatidyl glycerol and, possibly cerebroside like substances.
6. Methyl esters of the fatty acids of phosphatidyl choline and ethanolamine from both series were determined by GLC. In all samples 16:0, 18:0, 18:1, 18:2 and 18:3 acids were present besides of traces of 16:1 and 17:0. In contrast to neutral lipids the major acid of phospholipids is linoleic (53–58%), followed by oleic (8–24%) and linolenic acid (1–18%). The percentages of palmitic (4–8%) and stearic acids (tr.-1%) are small. Low lipid cells of series A differ from high lipid cells of series B by an increase of linolenic, and a decrease of linoleic acids, both in phosphatidyl choline and phosphatidyl ethanolamine.

     

In vivo studies on pathways for the biosynthesis of lecithin in the rat

The in vivo biosynthesis of lecithin in rats has been studied with the precursors choline-1,2-(14)C, ethanolamine-1,2-(14)C and methionine-CH(3)-(14)C or -CH(3)-(3)H. Lecithin synthesis from choline is rapid in all organs. No sex difference was observed in this pathway. The biosynthesis of lecithin by methylation of phosphatidyl ethanolamine is of quantitative significance in the liver, but not in extrahepatic tissues. More lecithin is synthesized by this pathway in female rats. In liver the lecithin synthesized via both pathways enters a common pool which is in rapid equilibrium with lecithin of blood plasma. A sex difference in the utilization of radioactive ethanolamine for the formation of phosphatidyl ethanolamine was observed (greater utilization in the female). Incorporation of ethanolamine into phospholipids of extrahepatic tissues was slow in both sexes. With labeled methionine as precursor the liver cytidine diphosphate (CDP) choline had a specific activity identical with that of liver lecithin after 20 min, while the specific activity of phosphoryl choline remained low. With labeled choline as precursor the phosphoryl choline reached a specific activity 50 times that of lecithin after 20 min, while the specific activity of CDP choline was only four times that of lecithin. These findings indicate that the reaction: CDP choline + diglyceride right harpoon over left harpoon phosphatidyl choline + CMP is freely reversible in vivo.     

Thin-layer chromatographic analysis of phospholipids in Echinostoma revolutum (Trematoda) adults.

Thin-layer chromatographic analyses were made of phospholipids extracted from adult Echinostoma revolutum (Trematoda) and from the nonnutrient medium in which worms were maintained. Identity of phospholipids was based on comparison with authentic lipid standards and on specific chemical detection tests. The most abundant phospholipids in the extract were phosphatidyl choline, phosphatidyl ethanolamine and phosphatidyl serine; lesser amounts of cerebrosides and lysophosphatidyl choline were detected also. Phospholipids detected in the incubation medium were essentially as described for extracts.     

Effect of feeding water washed neem (Azadirachta indica) seed kernel cake on the quality,lipid profile and fatty acid composition of goat meat

Three groups of five indigenous male goats 5–6 months of age, were offered control concentrate mixture (Group I) and those of Groups II and III were fed experimental concentrates containing 15 and 25% of water washed neem (Azadirachta indica) seed kernel cake (NKC). After 180 days of feeding the goats were slaughtered. Longissimus dorsi (LD) muscle from lumbar region was analysed for certain physico-chemical characteristics, organoleptic quality, detailed lipid profile and fatty acid composition; phosopholipids were fractionated into phosphatidyl inositide (PI), phosphatidyl serine (PS), lysophosphatidyl choline (LPC), lysophosphatidyl ethanolamine (LPE), sphingomyelin (SPH), phosphatidyl choline (PC) phosphatidyl ethanolamine (PE) and phosphatidic acid (PA). Fatty acids; capric, lauric, myristic, myristoleic, palmitic, palmitoleic, heptadecanoic, stearic, oleic, linoleic acid were also identified. Feeding of NKC did not affect slaughter weight and dressing out yield. The dressing percentage ranged between 42.2 and 43.8%. The pH, colour, moisture, total crude protein, different protein fractions; water extractable, salt extractable and content of NPN did not differ among the groups. There was a significant decrease in the total lipid content of LD of experimental groups. PC and PE were the major fractions accounting for 60% of total phospholipids. There was a significant increase in PC and LPC fractions while LPE+SPH, PE and PA fractions decreased in goats fed NKC. A significant increase was noticed in unsaturated fatty acid content and decrease in total saturates. It is concluded that NKC feeding has the ability of reducing lipid content and increasing the unsaturated fatty acids, which are considered to be beneficial in reducing the cholesterol level. It may be used beneficially as an alternative for costly conventional oil cakes for economic lean chevon production without affecting the quality of goat meat.     

Effects of γ-aminobutyric acid on 33Pi incorporation into rat brain phospholipids in vivo

The effects of γ-aminobutyric acid (GABA), bicuculline and strychnine on the incorporation $\text{in vivo}$ of ³³Pi into phospholipids of rat brain were studied at 10 and 30 minutes after intracisternal injection of the radionuclide. GABA inhibited labeling of phospholipids in the three brain regions studied at both times. Bicuculline by itself had no significant effect on ³³Pi incorporation, but totally blocked the inhibitory effect of GABA in all three brain regions. Strychnine by itself inhibited phospholipid labeling in the brain stem and forebrain, had no significant effect on GABA inhibition of ³³Pi incorporation in the cerebellum and forebrain, and partially blocked the GABA effect in the brain stem. GABA inhibited ³³Pi incorporation into phosphatidic acid, phosphatidylinositol, phosphatidyl choline and phosphatidyl ethanolamine but had no effect on phosphatidyl serine. The data suggest that the inhibitory effects of GABA on CNS phospholipid labeling are mediated specifically through GABA receptor sites.     

Phospholipids and phospholipid-bound fatty acids and aldehydes of spermatozoa and seminal plasma of rhesus monkeys.

The major components of the phospholipids of rhesus monkey spermatozoa are phosphatidyl choline (33%), phosphatidyl ethanolamine (25%), ethanolamine plasmalogen (16-1%), sphingomyelin (8-1%), choline plasmalogen (6-9%) and cardiolipin (4-5%). The major phospholipid-bound fatty acids are 16:0, 18:0, 18:1 and 22:6; the major fatty aldehydes are 15:0, 16:0 and 18:2. The same phospholipids are also present in the seminal plasma.     

Control of the potassium ion-stimulated adenosine triphosphatase of pig gastric microsomes: effects of lipid environment and the endogenous activator

The K⁺-stimulated ATPase activity associated with the purified gastric microsomes from the pig gastric mucosa can be completely inactivated by treatment with 15% ethanol for 60 s at 37 °C but not at 25 °C. Sequential exposure of the microsomes to 15% ethanol at 25 and 37 °C caused the release of 2.9 and 4.3% of the total membrane phospholipids, respectively, consisting entirely of phosphatidyl choline and phosphatidyl ethanolamine. The ethanol-treated (37 °C) membrane had high basal (with Mg²⁺ as the only cation in the assay mixture) activity, which was further enhanced during reconstitution with phosphatidyl choline or phosphatidyl ethanolamine. The high basal activities could be reduced to the normal control level by assaying the enzyme in presence of the “activator protein,” partially purified from the soluble supernatant of the pig gastric cells. Phosphatidyl choline was somewhat more effective than phosphatidyl ethanolamine in the restoration of the activity of the ethanol-treated enzyme while phosphatidyl serine, phosphatidyl inositol, and sphingomyelin were without any effect. Synthetic phosphatidyl choline with various fatty acid substitutions were tested for their effectiveness in the restoration of the ethanol-inactivated enzyme. The distearoyl (18:0), dioleoyl (18:1), and dilinoleoyl (18:2) derivatives of phosphatidyl choline were almost equally effective while dipalmitoyl (16:0) phosphatidyl choline was somewhat less effective in the reconstitution process. Cholesterol appeared to interfere with phosphatidyl choline in the restoration of the activity of ethanol-treated enzyme. The fatty acid composition of phosphatidyl choline and phosphatidyl ethanolamine extracted by 15% ethanol at 37 °C was clearly different than those of the total microsome. Our data suggest that the phospholipids extracted by 15% ethanol at 37 °C are derived primarily from the immediate lipid environment of the enzyme and ATP together with Mg²⁺ and K⁺ help the partially delipidated enzyme to retain the appropriate conformation for the subsequent reconstitution. Furthermore, ethanol appears to either release or inactivate the membrane-associated activator protein, demonstrated to be essential for the K⁺-stimulated activity of the pig gastric ATPase.     

In vitro incorporation of [14CH3]methionine into liver phosphatidylcholine in rats with vitamin E deficiency

The content of phosphatidyl choline, a terminal product of phosphatidyl ethanolamine methylation as well as in intensity in vitro incorporation of [14CH3]methionine into phosphatidyl choline of rat liver with E-hypovitaminosis are found to considerably decrease as compared to the norm. In this case the total content of phospholipids is practically the same.     

The molecular organization of nerve membranes

Summary The lipid content and composition from an axolemma-rich preparation isolated from squid retinal axons was analyzed.The lipids, which accounted for 45.5% of the dry weight of this membrane, were composed of 22% cholesterol, 66.7% phospholipids and 5.2% free fatty acids. The negatively charged species phosphatidyl ethanolamine (37%), phosphatidyl serine (10%) and lysophosphatidyl ethanolamine (4%) made up 51% of the phospholipids. The amphoteric phosphatidyl choline and sphingomyelin accounted for 39% and 4%, respectively.The relative distribution of fatty acids in each of the isolated phospholipids was studied. The most remarkable feature of these phospholipids was the large proportion of long-chain polyunsaturated fatty acids. The 226 acyl chain accounted for 37% in phosphatidyl ethanolamine, 21.7% in phosphatidyl choline, 17.5% on phosphatidyl serine and 20.3% in sphingomyelin (all expressed as area %).The molar fraction of unsaturated fatty acids reached 65% in phosphatidyl ethanolamine and 42.0 and 44.8% in phosphatidyl choline and phosphatidyl serine, respectively. The double bond index in these species varied between 1.0 and 2.6.The lipid composition of the axolemma-rich preparation isolated from squid retinal axons appears to be similar to other excitable plasma membranes in two important features: (a) a low cholesterol/phospholipid molar ratio of 0.61; and (b) the polyunsaturated nature of the fatty acid of their phospholipids.This particular chemical composition may contribute a great deal to the molecular unstability of excitable membranes.The preceding papers of this series were published inArchives of Biochemistry and Biophysics.     

Effects of choline and ethanolamine on the synthesis and breakdown of the inositol phospholipid (PI) system in Tetrahymena

Lower concentrations of choline chloride and ethanolamine (10^?3 M ; 10^?5 M ) increased phosphatidyl inositol (PI), phosphatidyl inositol monophosphate (PIP) and phosphatidyl inositol bisphosphate (PIP₂) level of Tetrahymena, while higher concentrations (10^?2 M ) decreased them. These two substances also influenced, however in a less obvious way, the transformation of inositol phospholipids. The experiments draw attention to the sensitivity of the precursors of the second messenger system at a phylogenetically low level.     

In vivo incorporation of l-[14C]serine into phospholipids and proteins of the subcellular fractions of developing rat brain

A study was conducted on the in vivo incorporation of l -[¹⁴C]-serine into the lipids and proteins of the various subcellular fractions of the developing rat brain before and during the stage of active myelination. The total radioactivity in the various fractions at 12 days of age was higher than that at 3 days, while the radioactive specific activity was reversed. The specific activities of the proteins and lipids were higher at 3 days of age with the exception of the subcellular fraction containing myelin. At both ages the lipids of the various cellular fractions had similar specific activities, a finding that suggests a common source for lipid biosynthesis. Incorporation of radioactivity into the various phospholipids was in the following order: phosphatidyl serine > phosphatidyl ethanolamine > phosphatidal serine > sphingomyelin and phosphatidyl choline. Of all the phospholipids, the plasmalogens increased most in total radioactivity during the period when meylination was most active. Serine-containing phospholipids appear to be most tightly bound to proteins. The brain mitochrondrial fraction contained most of the phosphatidyl serine decarboxylase activity with some activity in the nuclei. Biosynthesis of phosphatdyil ethanolamine through decarboxylation of phosphatidyl serine could take place in rat brain. Four unidentified radioactive metabolites were found in the acid-soluble fraction in addition to l -[¹⁴C]serine.     

Studies on triacylglycerol ester hydrolase from bat adipose tissue

Triacylglycerol ester hydrolase was isolated from bat adipose tissue and characterized. The partially purified enzyme had pH optimum of 8.6 and a K_m value of 0.6 mM. The enzyme was denaturated upon freezing and thawing, which was prevented by 25% glycerol. The enzyme was activated by EDTA and NaCl, while it was inhibited by serum and bovine serum albumin. Heparin, sodium fluoride and diisopropyl fluorophosphate had no effect on triacylglycerol ester hydrolase activity. It hydrolyzed triglycerides partially. Triacylglycerol ester hydrolase lost its activity during delipidation but it was reactivated by endogenous lipids and phospholipids, viz. phosphatidyl ethanolamine, phosphatidyl choline and sphingomyelin. The enzyme shows kinetic properties altogether different from lipoprotein lipase and hormone sensitive lipase