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At least 1,045 records · Page 58Linked to original sources
PubMed1990

Transport into brain of buthionine sulfoximine, an inhibitor of glutathione synthesis, is facilitated by esterification and administration of dimethylsulfoxide.

Buthionine sulfoximine (BSO), an inhibitor of glutathione synthesis, is poorly transported into the brain of adult mice, and only a slight decrease (approximately 10%) in the level of brain glutathione is found 30-60 min after intraperitoneal administration of BSO. When BSO is given as the ethyl ester, the brain level of BSO increases substantially after 5-15 min, and the glutathione level decreases by about 25% after 30-60 min. When BSO or its ester is given in 15% dimethylsulfoxide solution the brain levels of BSO are increased significantly and the brain glutathione levels are decreased by 20-35%. These observations suggest procedures that may be useful in decreasing the glutathione levels of the brains of adult animals. The finding that administration of BSO ethyl ester led to about a 25% decrease in the brain level of glutathione within 15 min suggests that a fraction of brain glutathione turns over very rapidly and may therefore be of special physiological significance.

Animals↗
PubMed1987

Effects of substrate composition on the esterification and hydrolysis activity of lysosomal acid sterol ester hydrolase.

Lipid microemulsions with various core and surface lipid compositions were prepared by co-sonication of cholesteryl esters, triolein (TO), egg phosphatidylcholine (egg PC), and cholesterol. The heterogeneous emulsion particle mixture was purified by gel filtration and particles with the size and general organization of low density lipoproteins were obtained. These lipid microemulsion particles were used for studies of the cellular metabolism of lipoprotein-derived cholesterol and cholesteryl esters as catalyzed by the enzyme acid sterol ester hydrolase (EC 3.1.1.13). The hydrolysis of cholesteryl oleate (CO) was more than twice and that of cholesteryl linoleate (CL) more than three times faster than the hydrolysis of cholesteryl stearate (CS) over the temperature range 25-39.6 degrees C. Both the synthesis and hydrolysis of cholesteryl esters were insensitive to the physical state of the microemulsion cores. The synthesis of cholesteryl esters by this enzyme was also insensitive to the ratios of cholesterol and egg PC in the microemulsion surface layers. Incorporation of triolein into the microemulsion cholesteryl ester core slightly increased the rate of cholesteryl ester synthesis. A decreasing fatty acyl chain length (C18:0 to C14:0) and an increasing degree of unsaturation (C18:0 to C18:2) enhanced the synthesis rate. It is suggested that the hydrolysis and synthesis of cholesteryl esters in microemulsions (and lipoproteins) take place only in the particle surface layer and that the rate of catalysis is directly dependent on the amount of substrate in this surface layer.

Animals↗
PubMed1983

Effect of chlorpromazine on lipid metabolism in aortas from cholesterol-fed rabbits and normal rats, in vitro: inhibition of sterol esterification and modification of phospholipid synthesis.

Chlorpromazine (CPZ), a major tranquilizer, was found to be a potent inhibitor of acylCoA:cholesterol acyltransferase (ACAT, EC 2.3.1.26) in isolated arterial microsomes and in intact arterial tissue from the rat and cholesterol-fed rabbit in vitro. In isolated rabbit arterial microsomes, CPZ resulted in a concentration-dependent inhibition of ACAT with 50% inhibition of [1-14C]oleoylCoA incorporation into [14C]cholesteryl esters occurring at 0.1 mM CPZ. CPZ also effectively inhibited the incorporation of [14C]oleate into triglycerides without affecting incorporation into diglycerides. Additionally, CPZ altered the pattern of arterial phospholipids synthesized from [1-14C]oleate. Incorporation into phosphatidylcholine was depressed while incorporation into phosphatidylinositol was increased. Since diglyceride synthesis appeared to be unaffected by CPZ, a redirection of phosphatidic acid into the CDP-diglyceride pathway of glycerolipid synthesis does not adequately account for the effect of CPZ on arterial phospholipid and triglyceride synthesis in these experiments.

Animals↗
PubMed1984

Augmentation of cholesterol esterification in the microsomal membrane by the removal of membrane-bound ribosomes.

Acyl-CoA: cholesterol O-acyltransferase (ACAT) activity in rough microsomes was enhanced (2-fold) by the removal (40%) of ribosomes from the microsomal membrane with RNase. Although EDTA was as efficient as RNase in the removal of ribosomes the stimulation (3.2-fold) of ACAT activity was even more, suggesting that additional effects were induced by EDTA. Reconstitution of EDTA-treated microsomes with ribosomes decreased the cholesterol-esterifying activity (40%) of the degranulated microsomes. Alternate possibilities were considered for the enhancement of ACAT activity by EDTA, namely, suppression of the hydrolysis of added palmitoyl-CoA substrate, the hydrolysis of cholesteryl ester, and the removal of metal suppressor of ACAT activity. Neither acyl-CoA hydrolase nor cholesteryl ester hydrolase activity was decreased after degranulation of microsomes. ACAT activity of EDTA-treated microsomes compared to the control was enhanced rather than suppressed after the addition of Ca2+, Mg2+, and Ba2+ ions whereas other metal ions (Co2+, Cu2+, Zn2+) almost completely suppressed ACAT activity in both the EDTA-treated and buffer-treated microsomes. It is concluded that the enhanced ACAT activity was largely due to the removal of ribosomes from the microsomal membrane.

Animals↗
PubMed1991

Selective conversion and esterification of monohydroxyeicosatetraenoic acids by human vascular smooth muscle cells: relevance to smooth muscle cell proliferation.

5-, 12-, and 15-hydroxyeicosatetraenoic acid (HETE), lipoxygenase metabolites of arachidonic acid that may modulate cell proliferation, were examined for their ability to affect the [3H]thymidine incorporation of human umbilical artery smooth muscle cells. We found that these hydroxy fatty acids inhibited the serum-induced [3H]thymidine incorporation of growth-arrested vascular smooth muscle cells in a similar dose-dependent manner. The inhibitory effect was dependent on the serum concentration used to stimulate cell growth. The higher the serum concentration, the lower the inhibitory effect of the HETE. In parallel experiments, the incorporation of HETEs into lipids of the smooth muscle cells was examined. After 20 h of incubation, we found that in the presence of 0.4% serum 70% of 3H-labeled 5-HETE was esterified into human vascular smooth muscle cell lipids. Twelve and eight percent, respectively, of 12- and 15-HETE were incorporated into smooth muscle cell lipids. Furthermore, we found that during the 20-h incubation of human umbilical artery smooth muscle cells with 12- and 15-HETE, these compounds were converted into metabolites with a chromatographic behavior on HPLC similar to that of diHETEs. 5-HETE was not converted into these polar metabolites. Increasing the serum concentration resulted in a decreased metabolism of all HETEs tested. Thus, the distinct differences between the metabolism of different HETEs by vascular smooth muscle cells does not reflect the proliferation inhibitory effect of these HETEs.

Cell Division↗