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Biomedical subjects

W C Chang

Publications and source records attributed to W C Chang.

At least 271 records · Page 15Linked to original sources
PubMed1983

Effects of purified eicosapentaenoic acid on arachidonic acid metabolism in cultured murine aortic smooth muscle cells, vessel walls and platelets.

The effects of highly purified eicosapentaenoic acid (97% pure) on the arachidonic acid cascade in isolated murine vascular cells and platelets were studied. The incorporation of eicosapentaenoic acid was not as active as that of arachidonic acid in platelets. The ratio of incorporation of eicosapentaenoic acid to arachidonic acid into platelet phospholipids was about 0.7. Analysis of the phospholipid fractions of platelets after labeling with 14C-eicosapentaenoic acid and 14C-arachidonic acid revealed that the incorporation of 14C-eicosapentaenoic acid into the fraction is significantly less than that of 14C-arachidonic acid, while the incorporation of both fatty acids into other phospholipid fractions was almost the same. On the other hand, no significant difference between either fatty acid in incorporation rate, kinetics or distribution in cellular phospholipids was found in cultured aortic smooth muscle cells. Following treatment with eicosapentaenoic acid, cells produced less prostacyclin from endogenous arachidonic acid than did control cells. This was not due to the decrease in fatty acid cyclooxygenase activity, but rather, due to the decrease in arachidonic acid content in cellular phospholipids. In addition, eicosapentaenoic acid was neither converted to prostaglandin I3 by the vascular cells nor to thromboxane A3 by platelets. Furthermore, similar results were also obtained by in vivo experiments in which rats were fed with eicosapentaenoic acid enriched diet.

Animals↗
PubMed1983

Lower temperature and orthophosphate control of alkaline phosphatase in a cold-requiring plant.

The elevated activity of alkaline phosphatase observed in roots and shoots of Verbascum rosettes grown in vitro at 15 degrees C may be the result of a reduced supply of orthophosphate. The rosette reveals greater activities of this enzyme under conditions of lower external phosphate or chilling temperature. Either of these treatments gives lower amounts of endogenous phosphate. The stimulation of phosphatase in tissues having lower levels of phosphate is thus a possible feature of other plant species which also display freezing tolerance.

Alkaline Phosphatase↗
PubMed1983

Calcium dependency of aortic smooth muscle cell migration induced by 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid. Effects of A23187, nicardipine and trifluoperazine.

We have previously reported that 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE), a 12-lipoxygenase product of arachidonic acid in platelets, is a potent chemoattractant for rat aortic smooth muscle cells. In the present study, the mechanism involved in 12-HETE-associated smooth muscle cell migration was investigated in relation to calcium mobilization in the cells. Migration of smooth muscle cells was measured by a filter membrane technique in modified Boyden chambers. Smooth muscle cell migration induced by 12-HETE increased with the increase of extracellular Ca2+ concentration and became maximal at the physiological Ca2+ concentration of 1.25 mM. The calcium ionophore A23187, at concentrations of 0.2 and 2.0 microM, significantly stimulated cell migration. Nicardipine, a potent calcium-entry blocker, significantly inhibited 12-HETE-associated smooth muscle cell migration at concentrations from 10(-9) to 10(-5) M. Concentrations of trifluoperazine from 10(-9) to 10(-5) M and W-7 at 10(-5) M, which are specific inhibitors of calmodulin, also significantly inhibited cell migration induced by 12-HETE. Cytochalasin B at 1.0 and 10 microM, and colchicine at 0.1 and 1.0 microM concentrations drastically inhibited cell migration, indicating that actin-containing microfilaments and microtubules are involved in smooth muscle cell migration. These findings indicated that the stimulation of smooth muscle cell migration by 12-HETE is a highly calcium-dependent process and suggest that 12-HETE might act at the initial stage of smooth muscle cell migration through enhancing calcium influx through plasma membrane and thus stimulating cell migration.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1983

Changes in arachidonate metabolism in aortas and platelets in aging rats.

Prostacyclin formation by aortas, thromboxane biosynthesis and 12-lipoxygenase pathway in platelets as a function of age was investigated. Our results indicate an age-related decrease in prostacyclin production by aortas, while no significant change in thromboxane biosynthesis in platelets from mature (12 month old) to senescent (24 month old) rats was observed. Evidence is also presented indicating a decrease in 12-L-hydroperoxy-5,8,10,14-eicosatetraenoic acid (12-HPETE) peroxidase activity in platelets as a function of age.

6-Ketoprostaglandin F1 alpha↗
PubMed1983

Induction of fatty acid cyclooxygenase in rat aortic smooth muscle cells by estradiol.

We have previously reported that estradiol stimulates prostacyclin biosynthesis in cultured rat aortic smooth muscle cells by increasing fatty acid cyclooxygenase activity, and induction of new protein biosynthesis is involved since the effect of estradiol is blocked by cycloheximide treatment. In order to see whether estradiol stimulates de novo biosynthesis of fatty acid cyclooxygenase in cells, a specific radioimmunoassay of fatty acid cyclooxygenase was used to measure the enzyme. Estradiol significantly increased immunoreactive fatty acid cyclooxygenase in cells. Consequently, increase in cyclooxygenase activity results in the production of more prostaglandin endoperoxides for final increased synthesis of prostacyclin in these cells.

Animals↗
PubMed1982

Stimulation of 12-lipoxygenase activity in rat platelets by 17 beta-estradiol.

The effects of estradiol on the endogenous fatty acid (specifically, arachidonic acid) composition of cellular phospholipid fractions and the 12-lipoxygenase activity in rat platelets in vivo were studied. Estradiol had no significant effect on the endogenous fatty acid composition of cellular phospholipid fractions. However, estradiol significantly increased 12-lipoxygenase activity in platelets in a dose-dependent manner. The stimulatory effect of estradiol on platelet lipoxygenase was blocked by the anti-estrogen nafoxidine hydrochloride which was injected simultaneously together with estradiol in vivo, suggesting that the effect in target cells was due directly to estradiol.

Animals↗
PubMed1982

Effects of reduced glutathione on the 12-lipoxygenase pathways in rat platelets.

Arachidonic acid is converted into several more polar products in addition to 12-l-hydroperoxyeicosa-5,8,10,14-tetraenoic acid (12-HPETE) and 12-l-hydroxyeicosa-5,8,10,14-tetraenoic acid (12-HETE) by the cytosol fractions of rat platelets. The more polar products are formed via the lipoxygenase pathways in the same way as are 12-HPETE and 12-HETE, since their formation is not inhibited by indomethacin but by eicosa-5,8,11,14-tetraynoic acid (ETYA). The presence of 0.5-1.5mm-reduced glutathione (GSH) in the reaction mixture prevents the formation of the more polar products and produces 12-HETE as the only metabolite from arachidonic acid by the 12-lipoxygenase pathway. l-Cysteine has the same effect as GSH. However, oxidized glutathione (GSSG) and l-cystine are not able to prevent the formation of the more polar products. The results indicate that 12-HPETE peroxidase in the 12-lipoxygenase pathway is a GSH-dependent peroxidase and the more polar products might be formed from the non-enzymic breakdown of the primary 12-lipoxygenase product of 12-HPETE, owing to insufficient capability of the subsequent peroxidase system to completely reduce 12-HPETE to 12-HETE. Thus the presence of GSH in the reaction mixture offers a convenient and precise cell-free assay system for 12-lipoxygenase in rat platelets. Routine assays of 12-lipoxygenase are carried out in the presence of 1mm-GSH in the reaction mixture. The synthesis of 12-HETE by 12-lipoxygenase is linear during the first 4 min of incubation at 37 degrees C, and has a pH optimum of 7.7. The 12-lipoxygenase reaches half-maximal activity at an arachidonate concentration of 20mum. Fractionation of cell homogenates indicates that the cytosol fraction possesses almost all the 12-lipoxygenase activity, whereas the microsomal fraction exhibits little enzyme activity.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1982

Comparative effect of lipoxygenase products of arachidonic acid on rat aortic smooth muscle cell migration.

We investigated the effects of mono-hydroxyeicosatetraenoic acids (HETEs) and N-formyl-methionyl-leucyl-phenylalanine (F-Met-Leu-Phe) on rat aortic smooth muscle cell migration in modified Boyden chambers. 12-HETE showed the most potent stimulatory effect on smooth muscle cell migration among the mono-HETEs tested. The optimal concentrations for cell migration were 3 X 10(-15) and 3 X 10(-13) g/ml for 12-HETE and 10(-8) g/ml for 15-HETE, 5-HETE and F-Met-Leu-Phe were inactive with these cells. As 12-HETE is biosynthesized from arachidonic acid by the 12-lipoxygenase pathway in platelets and macrophages, and 15-HETE by the 15-lipoxygenase pathway in granulocytes, the present results indicate an important role for such cells in the early phase of atherosclerosis.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1982

Platelets stimulate aortic smooth muscle cell migration in vitro. Involvement of 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid.

The migration of rat aortic smooth muscle cells was measured in modified Boyden chambers. Smooth muscle cells were motile in vitro and their migration was stimulated (time- and dose-dependently) by a platelet-derived factor. Treatment of platelets with indomethacin resulted in a significant increase in smooth muscle cell migration, whereas treatment with 5,8,10,14-eicosatetraenoic acid inhibited it. Purified 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid at a very low concentration (6 x 10(-15)-6 x 10(-13) g/ml) significantly stimulated smooth muscle cell migration. The locomotion induced by 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid was chemokinetic. These findings point to the physiological importance of a platelet 12-lipoxygenase product of arachidonic acid in the early phase of atherosclerosis.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1982

Comparison of prostaglandin biosynthetic activity between porcine aortic endothelial and smooth muscle cells in culture.

Prostaglandin biosynthetic activity of miniature-pig aortic endothelial cells was compared with that of smooth muscle cells in culture. When used as homogenates, endothelial cells produced mainly PGE2 and 6-ketoPGF1 alpha (degradated product of PGI2) from arachidonic acid, while they produced a large amount of PGF2 alpha in addition to these when used as intact cells. Intact smooth muscle cells and their homogenates produced PGE2 as a major product. 6-KetoPGF1 alpha was produced by smooth muscle cells in the first few generations and became undetectable after several cultivations. 6-KetoPGF1 alpha and PGE2 were produced by intact or endothelium-depleted aortas. Our results suggest that both endothelial cells and smooth muscle cells in porcine aorta possess PGI2 and PGE2 biosynthetic activities. The subcultivation of smooth muscle cells, but not endothelial cells, in vitro resulted in the rapid disappearance of PGI2 synthetase activity. The PGI2 biosynthetic activity of endothelial cells was several fold higher than that of smooth muscle cells. Porcine smooth muscle cells' low ability to produce PGI2 may offer a reason why atherosclerosis is easily developed in pigs.

6-Ketoprostaglandin F1 alpha↗
PubMed1981

Effects of estradiol on the metabolism of arachidonic acid by aortas and platelets in rats.

We have previously reported that estradiol treatment stimulates prostacyclin production by cultured rat aortic smooth muscle cells, through the stimulation of fatty acid cyclooxygenase and prostacyclin synthetase activities. In order to see whether estradiol stimulates the fatty acid cyclooxygenase activity in platelets, intact rats were treated with estradiol, and thromboxane biosynthesis in platelets and prostacyclin production by aortas were investigated. Estradiol significantly stimulates prostacyclin production by aortas. However, no significant effect on thromboxane biosynthesis in platelets is observed. Our present results support the idea that estradiol would be a protective hormone in atherosclerotic heart disease.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1981

Triiodothyronine stimulates prostacyclin production by rat aortic smooth muscle cells in culture.

The effect of triiodothyronine (T3) on prostacyclin production in rat aortic smooth muscle cells was investigated by using an intact cell assay system. T3 at its physiological concentrations has no significant effect on smooth muscle cell proliferation, but it does significantly stimulate prostacyclin production by the cells. Maximum stimulation of prostacyclin production is obtained when cells are treated with T3 for 4 consecutive days. The dose--response curve shows a linear relationship between the stimulation of prostacyclin production and T3 concentrations in the range 0.007--10 microgram/dl. The maximal prostacyclin production by T3-treated cells (at a concentration of 10 microgram/dl), is 270% compared with control cells. T3 treatment shows no significant effect on phospholipase (and/or lipase) activities. Our results suggest that thyroid hormone might play an important physiological role in the protection of arteries from atherosclerotic changes by stimulating prostacyclin production in arterial smooth muscle cells.

Animals↗
PubMed1981

Biosynthetic rates of proteins having the characteristics of glucocorticoid receptors in adipocytes of mature and senescent rats.

An affinity chromatography technique has been utilized to compare the rates of putative glucocorticoid receptor biosynthesis in epididymal fat pad adipocytes of mature and senescent Wistar rats. Biosynthetic rates appear to be linear for at least 3 hours in both age groups, but are reduced by about one-half in the senescent cells. In contrast, incorporation of labeled amino acids into total protein is not altered with aging in this system. Thus, reduction in putative glucocorticoid receptor biosynthetic rate may reflect the effects of senescence on the expression of only a small part of the genome.

Aging↗
PubMed1981

Human beta-endorphin: synthesis and biological activity of analogs with substitutions in positions 2, 9, 18, 27 and 31.

Four analogs of the opioid peptide human beta-endorphin (Bh-EP) have been synthesized: [D-Lys9, Phe27, Gly31]-beta h-EP, [D-PHe18,Phe27,Gly31]-beta h-EP, [D-Thr2,D-Lys9,Phe27,Gly31]-beta h-EP, and [D-Thr2,D-Phe18,Phe27,Gly31]-beta h-EP. All are practically indistinguishable from beta h-EP in the guinea pig ileum assay. All show diminished analgesic potency in the mouse tail-flick assay.

Amino Acid Sequence↗