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Arachidonic acid metabolism by erythrocytes   总被引:2,自引:0,他引:2  
Rabbit, chicken, rat, and dog erythrocytes (10(9) cells/ml) synthesized immunologically active 12-hydroxyeicosatetraenoic acid (12-HETE) when stimulated by the Ca2+ ionophore, A-23187. The levels of immunologically active hydroxyeicosatetraenoic acid were independent of the number of white blood cells and platelets in the erythrocyte suspensions. Two products were resolved by high performance liquid chromatography; one product was identified as 12-HETE, while a second product appeared to be a dihydroxyeicosatetraenoic acid. Radiolabeled arachidonic acid was incorporated into phospholipids. Phosphatidylcholine and phosphatidylethanolamine were primary sources of the 12-HETE and dihydroxyeicosatetraenoic acid, all of which were released from the cells.  相似文献   

3.
Arachidonic acid metabolism in filarial parasites   总被引:4,自引:0,他引:4  
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1. Arachidonic acid was metabolized by lipoxygenase and prostaglandin synthetase enzymes systems in the perfused ram testis. 2. The major product of the prostaglandin synthetase was 6-keto-PGF1 alpha (6KF). 3. Addition of testosterone resulted in a significant increase in the 6KF. 4. Arachidonic acid (AA) as well as testosterone penetrated the perfused testis. 5. Both 15-HPETE and 15-HETE, the products of the 15-lipoxygenase enzyme, were detected. 6. Addition of 0.1% BSA changed the pattern of the oxidized arachidonic acid metabolism.  相似文献   

6.
Melittin, the predominant fraction of bee venom proteins, was studied in an experimental model of human neutrophil granulocytes to reveal its influence on eicosanoid release, metabolism and receptor function in relation to intracellular calcium metabolism. Melittin (2 mumol/l) was as potent as the calcium ionophore A23187 (10 mumol/l) for activation of 5-lipoxygenase, releasing arachidonate only from phosphatidyl-choline and phosphatidyl-ethanolamine of cellular membranes, as judged from the decreases in radioactivity by 15.4% and 30.5%, respectively. The mechanism responsible for the release of arachidonate from cellular membranes is closely coupled to cellular calcium metabolism, and melittin was found to promote calcium entry through receptor gated calcium channels, probably due to an activation of phospholipase A(2). Furthermore, a down-regulation of leukotriene B(4) receptors was seen. The maximal number of binding sites per cell was reduced from a median of 1520 to 950 with melittin (1 mumol/l). The study has revealed some factors important for the inflammatory mechanisms mediated by melittin.  相似文献   

7.
Turkeys are hypertensive compared to mammals of similar size. In vitro synthesis of thrombocyte thromboxane B2 (TxB2), 12L-hydroxy-5, 8, 10 heptadecatrienoic acid (HHT), 12L-hydroxy-5,8,10,14-eicosatetraenoic acid (HETE) and aortic prostaglandin (PG) production was studied in one to ten month old domestic white turkeys. Compared to normal human platelets, TxB2 production was increased (55.4 vs. 31.4%) and HETE production was markedly reduced (6.5 vs. 34.6%) in control thrombocytes. Similar to human platelets in which cyclooxygenase inhibition with aspirin results in an increase in HETE production, block of the thrombocyte enzyme with aspirin doubled the production of HETE. In vitro conversion of radiolabeled arachidonic acid (AA) showed that the primary PG produced by turkey aorta was PGE2. A 6-keto immunoreactive PG was present which comigrated with authentic 6-keto PGF1, but failure of the aortic supernatant to inhibit adenosine diphosphate or AA induced platelet aggregation suggested that PGI2 was not produced. The vasodepressor potency of PGE1, PGE2 and PGI2 was altered in awake turkeys with PGE1 and PGE2 having five times the hypotensive effect as PGI2. In addition, conversion of AA to PGE2 by aorta in one month turkeys was greater (17.3 vs. 9.2%) than in ten month old turkeys. Systemic arterial pressure was increased in the ten month old turkeys (188 mmHg) compared to one month old turkeys (143 mmHg). Thus, both vascular AA metabolism and the vasodepressor potencies of PGE2 and PGI2 are altered and the activity of the lipoxygenase pathway in thrombocytes is limited in the turkey.  相似文献   

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Arachidonic acid metabolism in purified human lung mast cells   总被引:9,自引:0,他引:9  
Arachidonic acid metabolism has been explored in preparations of purified human lung mast cells prelabeled with arachidonic acid (AA). Cells were of 83 to greater than 96% purity, and each experiment was performed with four to six different preparations of mast cells. After overnight culture of the purified cells in the presence of 3H-AA, followed by extensive washing in buffer, mast cell uptake of labeled AA was 61.4 +/- 14.8 pmol/10(6) cells with 21 +/- 2.4% of the label in phospholipids, 73 +/- 2.1% in neutral lipids, and 3.6 +/- 0.8% as free AA. Analysis of the distribution of radioactivity in phospholipid classes revealed 51.4 +/- 5.5% of the label in phosphatidylcholine, 14.5 +/- 1.6% in phosphatidylinositol, 12.0 +/- 3.0% in phosphatidylethanolamine, and 9.1 +/- 2.4% in sphingomyelin, with the rest in other phospholipid classes. Challenge of these cells with an optimal concentration of anti-IgE led to the release of 20 +/- 4.0% of cellular histamine and to a reduction in labeled phosphatidylcholine and phosphatidylinositol to 75.5 +/- 8.8% and 84.2 +/- 4.5% of the control levels, respectively, (p less than 0.05); anti-IgE challenge produced no statistically significant change in the quantities of other labeled phospholipids. Activation of human lung mast cells with anti-IgE led to the release of 3.4 +/- 1.3% of the cellular 3H as AA and AA metabolites (1.5 +/- 0.6% as unmetabolized AA) in conjunction with 16 +/- 4.3% of the cellular histamine. Although activation of human lung mast cells with ionophore A23187 caused 70 +/- 1.1% histamine release, a similar quantity of AA and AA metabolites was released (a total of 4.0 +/- 0.8% with 2.3 +/- 1.5% as unmetabolized AA). Analysis of the released metabolites by liquid scintillation spectrometry after high performance liquid chromatography separation showed that approximately equal amounts of metabolites were produced after mast cell activation with anti-IgE and ionophore A23187. In this series of experiments approximately equal amounts of cyclooxygenase and lipoxygenase products were generated.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   

10.
Turkeys are hypertensive compared to mammals of similar size. In vitro synthesis of thrombocyte thromboxane B2 (TxB2), 12L-hydroxy-5,8,10 heptadecatrienoic acid (HHT), 12L-hydroxy-5,8,10,14-eicosatetraenoic acid (HETE) and aortic prostaglandin (PG) production was studied in one to ten month old domestic white turkeys. Compared to normal human platelets, TxB2 production was increased (55.4 vs. 31.4%) and HETE production was markedly reduced (6.5 vs. 34.6%) in control thrombocytes. Similar to human platelets in which cyclooxygenase inhibition with aspirin results in an increase in HETE production, block of the thrombocyte enzyme with aspirin doubled the production of HETE. In vitro conversion of radiolabeled arachidonic acid (AA) showed that the primary PG produced by turkey aorta was PGE2. A 6-keto immunoreactive PG was present which comigrated with authentic 6-keto PGF1 alpha, but failure of the aortic supernatant to inhibit adenosine diphosphate or AA induced platelet aggregation suggested that PGI2 was not produced. The vasodepressor potency of PGE1, PGE2 and PGI2 was altered in awake turkeys with PGE1 and PGE2 having five times the hypotensive effect as PGI2. In addition, conversion of AA to PGE2 by aorta in one month turkeys was greater (17.3 vs. 9.2%) than in ten month old turkeys. Systemic arterial pressure was increased in the ten month old turkeys (188 mmHg) compared to one month old turkeys (143 mmHg). Thus, both vascular AA metabolism and the vasodepressor potencies of PGE2 and PGI2 are altered and the activity of the lipoxygenase pathway in thrombocytes is limited in the turkey.  相似文献   

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Preimplantation embryos of many species are known to synthesize prostaglandins. These tissue hormones are believed to influence embryonic metabolism, as well as embryo-maternal interaction during implantation although their putative role(s) remains obscure. Here, prostaglandin production by blastocysts from cynomolgus monkeys (Macaca fascicularis) was examined qualitatively during in vitro culture. Tritium labelled arachidonic acid was metabolized to 6 keto-prostaglandin F1 alpha, 2,3-dinor-prostaglandin F1 alpha and thromboxane B2, as characterized by HPLC separation. Also, 6-keto-prostaglandin F1 alpha, and thromboxane B2 as characterized by HPLC separation. Also, 6-keto-prostaglandin F1 alpha and thromboxane B2 were identified by specific RIA's. Our data suggest that the main arachidonic acid metabolites produced by blastocysts of cynomolgus monkeys are prostacyclin and thromboxane.  相似文献   

13.
Human peripheral blood mononuclear cells were isolated and assessed for the presence of contaminating polymorphonuclear leukocytes and platelets. Incubations of these cell isolates were performed in the presence or absence of the calcium ionophore A23187 and/or 1-14C-labeled or unlabeled arachidonic acid. Using reverse phase high pressure liquid chromatography with simultaneous monitoring of ultraviolet light absorption at 229 and 280 nm and, where appropriate, of radioactivity, our studies reveal that human peripheral blood mononuclear cells generate leukotrienes C4 and B4 (LTC4 and LTB4) and 5-hydroxyeicosatetraenoic acid (5-HETE) following stimulation with A23187. The ratio of LTC4 to LTB4 was approximately 10-fold greater among the mononuclear cells than among similar incubations of polymorphonuclear leukocytes. Furthermore, the mononuclear cells failed to metabolize LTB4 into the omega-hydroxy or omega-carboxy derivatives that were always present in, and very characteristic of incubations of polymorphonuclear leukocytes. Depletion of monocytes from the mononuclear cells by double adherence resulted in virtual loss of the generation of 5-lipoxygenase-derived products by the remaining nonadherent cells, supporting the conclusion that the monocytes and not the lymphocytes were the source of LTC4, LTB4, and 5-HETE. The presence of both 12-HETE and the cyclooxygenase-derived 12-hydroxyheptadecatrienoic acid correlated with the degree of platelet contamination, suggesting that the platelets account for the presence of these compounds.  相似文献   

14.
The hypotensive activity of arachidonic acid is more important by intraaortic than by intravenous injection, in the rat. The evisceration of the animal abolishes this difference and reduces the activity of arachidonic acid. This action is not accompanied by thrombopenia and is only observed with high doses of arachidonic acid in this species. The hypotensive activity is inhibited by indomethacin but not by tranylcypromine.  相似文献   

15.
It was found that calcium exchange disturbances under vitamin E deficiency is due to changes in the metabolism of vitamin D. In vitamin E-deficient rats the serum blood levels of hydroxyvitamin D (25-OHD) showed no significant changes, whereas the concentration of the hormonal form of 1.25-hydroxyvitamin D [1.25(OH)2D], decreased by 40%. In vitro studies showed that the 25-hydroxylase D3 activity in the livers of rats with E-avitaminosis had a tendency to decrease (by 22%), whereas that of 24-hydroxylase dropped drastically (by 52%). The serum blood levels of the parathyroid hormone (PTH) and kidney levels of cAMP under E-avitaminosis were significantly lowered. Preincubation of kidney slices with the adenylate cyclase activator, forskolin, increased the activity of 1-OHase in about the same degree as that in vitamin E-rich rats. The free radical scavenger, BHT, added to kidney slices suppressed the activity of the both enzymes; this finding testifies to the low O2-binding affinity of these monooxygenases. The content of 1.25(OH)2D3 receptors occupied in vivo in the kidneys of vitamin E-deficient rats decreased 2.5-fold; however, the binding of 1.25(OH)2D3-receptor complexes to heterologous DNA was unaffected thereby. The vitamin deficiency in vivo results in the inhibition of vitamin D metabolism in the liver and kidney concomitant with the formation of active metabolites and decreases the concentration of hormone-receptor complexes in target tissues.  相似文献   

16.
The ability of rabbit fetal membranes to convert arachidonic acid to both lipoxygenase and cyclooxygenase products was studied by separation and identification of products derived from incubations of 1-14C-arachidonate with subcellular fractions obtained by differential centrifugation of tissue homogenates. Both amnion and splanchnopleure (the chorion-equivalent of the rabbit) produced a mixture of 11-, 12-, and 15-hydroxyeicosatetraenoic acids when stimulated by calcium ions; these products were produced in greater quantity in middle pregnancy (20-22d) than later (28-30d). Cyclooxygenase products included PGD2, PGE2, TxB2 and PGF2 alpha, all of which were made more actively in late pregnancy than the middle in both amnion (which was more active) and chorion-equivalent. These data suggest that arachidonate metabolism by rabbit fetal membranes in middle pregnancy is directed primarily toward production of monohydroxy fatty acids, but that as pregnancy nears term, the PG-producing enzymes are induced, preparing the uterine smooth muscle for parturition.  相似文献   

17.
The widely conserved preferential accumulation of α-tocopherol (α-TOH) in tissues occurs, in part, from selective postabsorptive catabolism of non-α-TOH forms via the vitamin E-ω-oxidation pathway. We previously showed that global disruption of CYP4F14, the major but not the only mouse TOH-ω-hydroxylase, resulted in hyper-accumulation of γ-TOH in mice fed a soybean oil diet. In the current study, supplementation of Cyp4f14−/− mice with high levels of δ- and γ-TOH exacerbated tissue enrichment of these forms of vitamin E. However, at high dietary levels of TOH, mechanisms other than ω-hydroxylation dominate in resisting diet-induced accumulation of non-α-TOH. These include TOH metabolism via ω-1/ω-2 oxidation and fecal elimination of unmetabolized TOH. The ω-1 and ω-2 fecal metabolites of γ- and α-TOH were observed in human fecal material. Mice lacking all liver microsomal CYP activity due to disruption of cytochrome P450 reductase revealed the presence of extra-hepatic ω-, ω-1, and ω-2 TOH hydroxylase activities. TOH-ω-hydroxylase activity was exhibited by microsomes from mouse and human small intestine; murine activity was entirely due to CYP4F14. These findings shed new light on the role of TOH-ω-hydroxylase activity and other mechanisms in resisting diet-induced accumulation of tissue TOH and further characterize vitamin E metabolism in mice and humans.  相似文献   

18.
Arachidonic acid (AA) evoked a dose-dependent increase in the accumulation of inositol phosphates in cultured bovine adrenal chromaffin cells, and this effect was specific for AA. AA also induced a rise in [Ca2+]i, but this rise was markedly reduced by removal of extracellular Ca2+. AA-induced accumulation of inositol phosphates was absolutely dependent on extracellular Ca2+, and nicardipine and nifedine partially reduced it but verapamil had no effect. Moreover, AA dose-dependently stimulated catecholamine release from chromaffin cells in the presence of ouabain, and this effect was specific for AA. AA-induced catecholamine release in the presence of ouabain was also inhibited by nicardipine and nifedipine but not by verapamil. Furthermore, the phospholipase C inhibitor neomycin inhibited the release. These results taken together suggest that AA stimulates catecholamine release in the presence of ouabain by stimulation of phosphoinositide metabolism in a Ca2(+)-dependent manner.  相似文献   

19.
Rat brain minces were used to investigate the effects of nucleotides on the metabolism of arachidonic acid in nerve tissue. Brain free fatty acids, neutral lipids and phospholipids, were radiolabeled in vivo following intracerebral injection of [3H]arachidonic acid. Minces were prepared from the radiolabeled cerebra and were incubated in a modified Krebs-Ringer buffer with and without various nucleotides. The incubation-induced accumulation of unesterified [3H]arachidonate was reduced in the presence of CDPcholine, ATP, CTP, GTP, and UTP. These nucleotides inhibited choline and inositol glycerophospholipid hydrolysis. They also reduced the amount of labeled diglycerides. However, CDPethanolamine had no effect on arachidonic acid metabolism in the mince preparation and CMP appeared to stimulate further hydrolysis of choline glycerophospholipids, resulting in increased accumulation of [3H]arachidonic acid and labeled diglycerides. We suggest that the production of unesterified [3H]arachidonate and labeled diglycerides is due to the involvement of more than one catabolic reaction, since the high energy nucleotides had similar effects on fatty acid accumulation, but different effects on phospholipid labeling.  相似文献   

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