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1.
Renal tubular epithelial cells isolated from dog and pig kidney (MDCK and LLC-PK1, respectively) transport water and electrolytes in culture. MDCK cells resemble collecting tubule cells by additional, but not all, morphologic and biochemical criteria. It has previously been reported that PGE2 appears to regulate transport activity by MDCK cells as well as their proliferation. We investigated prostaglandin biosynthesis by MDCK and LLC-PK1 cells and assessed the effects of peptide hormones, bradykinin and vasopressin, on the cells' prostaglandin biosynthesis. Thin-layer chromatography of radioactive products released by MDCK cells labelled with octatritiated of [14C] arachidonic acid indicated the presence of materials comigrating with PGE2, PGI2 (detected as 60oxo0PGF1α) and PGF2α, in decreasing order of abundance. Maclofenamate inhibited the biosynthesis of all radioactive peaks comigrating with PGs, thus confirming their identities as product of fatty acid cyclo-oxygenase activity. The chemical identities of [3H] PGE2 and [3H] 6-oxo-PGF1α made by the cells were further confirmed by treatment with KOH. Radioimmunoassay of culture fluids incubated with MDCK cells verified that PGE2 was the most abundant prostaglandin. Tranylcypromine, thought to be a specific inhibitor of prostacyclic synthetase, inhibited PGE2 as well as PGI2 biosynthesis indicating a lack of specificity of the inhibitor. The observation of PGE2 and PGF2α as respectively the most and least abundant prostaglandinds made by MDCK was in disagreement with results from another laboratory in which the reverse order of abundance was found. This suggests the presence of more than one cell line identified as MDCK but having different biochemical properties.Bradykinin stimulated acylhydrolase activity as well as PGE2 and PGI2 biosynthesis in MDCK cells while vasopressin had little or no effect. These results support the hypothesis that bradykinin's natriuretic effects may be mediated by prostaglandinds and that vasopressin is unlikely to acutely stimulate prostaglandin biosynthesis in collecting tubule cells invivo. Endogenous PGE2 may also regulate the proliferation of MDCK cells in culture.In contrast to MDCK cells, LLC-PK1 cells lacked significant prostaglandin biosynthetic capability as documented by radiometric thin-layer chromatography and radioimmunoassay. This suggests that prostaglandins may have a modulatory rather than an obligatory role in regulating transport activity by tubular epithelial cells.  相似文献   

2.
Effect of various prostaglandins on the release of arachidonic acid from [14C]arachidonic acid labeled fibroblasts was studied. Prostaglandin(PG) F was found to enhance the release of radioactive arachidonic acid from the cells. The stimulatory effect was dose dependent, and was greater than that of bradykinin. The active compounds can be ranked in potency for the release of arachidonic acid from the pre-labeled cells per cent of control: PGF(200.1%)>PGF (141.8%)>PGD2 (137.1%)>thromboxane B2 (113.7%)>PGE2 (109.4%). On the other hand, PGI2 showed a strong inhibitory effect on the arachidonic acid release from the pre-labeled cells (the value was only 69% of the control), while 6-ketoPGF, an end metabolite of PGI2, had no effect.  相似文献   

3.
Serum and/or arachidonic acid stimulated prostaglandin production by dog kidney (MDCK) cells. Epidermal growth factor (EGF) at concentrations of 10?9 to 10?10 M stimulated the biosynthesis of prostaglandins by MDCK cells but not that by human fibroblasts (D-550), mouse fibroblasts (3T3), transformed mouse fibroblasts (MC5-5), and rabbit aorta endothelial cells (CLO). EGF also stimulated the release of radioactivity from MDCK cells radioactively labelled with [3H]arachidonic acid.  相似文献   

4.
Our previous study indicated that, in the isolated rabbit heart, perfusion with Ca2+ free Krebs Henseleit buffer (KHB) results in increased conversion of exogenous arachidonic acid to PGE2 and 6-keto-PGF, probably as the result of increased availability of substrate to cuclooxygenase. Since perfusion with Ca2+ free buffer is known to cause alterations in the cardiac content of various mono- and divalent cations, the present study was performed to determine: a) The relationship between the conversion of exogenous arachidonic acid to prostaglandins and cardiac content of Na+, K+, Ca2+ and Mg2+; and b) Whether enhanced arachidonic acid conversion to prostaglandins during Caa2+ free perfusion is due to reduced incorporation of this fatty acid into tissue lipids. Perfusion of the rabbit heart with Ca2+ free buffer produced a significant reduction in the tissue content of Na+, K+, Ca2+ and Mg2+. However, the production of 6-keto-PGF from exogenous arachidonic acid was linearly correlated with tissue Mg2+. These observations, together with our finding that perfusion with Ca2+ free KHB reduced the incorporation of [3H] arachidonic acid into tissue lipids, suggests that Ca2+ free perfusion may, by reducing the activity of arachidonyl CoA synthetase (a Mg2+ dependent enzyme), decrease the acylation of arachidonic acid into lipids, thus increasing the availability of arachidonic acid to cyclooxygenase.  相似文献   

5.
Two tumor promoting phorbol-12,13-diesters, 12-0-tetradecanoyl-phorbol-13-acetate and phorbol-12,13-didecanoate, at concentrations of 10?9 to 10?10 M, stimulated prostaglandin production by dog kidney (MDCK) cells cultured in serum-supplemented medium. The non-tumor producing phorbol diester, 4α-phorbol-12,13-didecanoate, at a concentration of 10?7 M, had no effect. The two biologically active phorbol diesters, but not the non-tumor promoting analog, stimulated deacylation of the cellular phospholipids of MDCK cells radioactively labelled with [3H]arachidonic acid. Most of the arachidonic acid was converted into prostaglandins.  相似文献   

6.
Supplementation of growing MDCK canine kidney tubular epithelial cultures with linoleic acid produced a 3.6- to 4.9-fold increase in bradykinin-stimulated PGE2 release as measured by radioimmunoassay. Under these conditions the cell phospholipids contained 3.9-times more linoleic acid and 5.6-times more arachidonic acid, with the inositol, ethanolamine and choline phosphoglycerie fractions becoming enriched in arachidonic acid. By contrast, supplementation with arachidonic acid did not enhance bradykinin-stimulated PGE2 release even though the arachidonic acid content of the cell phospholipids was increased 8.8-fold. The distribution of radioactive prostaglandin products was unchanged by these fatty acid enrichments, with PGE2 accounting for 55 to 68% of the total output from [1-14C]arachidonic acid. Linoleic acid supplementation also produced a 2.5-fold increase in PGE2 formation stimulated by extracellular arachidonic acid, whereas supplementation during culture with arachidonic acid caused a 55 to 80% inhibition. This difference cannot be accounted for by changes in the ability of the cells to incorporate extracellular arachidonic acid. it is suggested that at least some of the effects of linoleate supplementation on prostaglandin production are due to the resulting enrichment of the intracellular phospholipid substrate pools with arachidonic acid. In addition, it appears that prolonged exposure to arachidonic acid during culture has an overriding inhibitory effect on prostaglandin production even though the total cell lipids bocome highly enriched in arachidonate.  相似文献   

7.
A renal medulla 100,000g pellet metabolized arachidonic acid, C20:4, to the previously described prostaglandins prostaglandin E2, 6-ketoprostaglandin F, thromboxane B2, 12-hydroxyheptadecatrienoic acid, and 11-hydroxyeicosatetraenoic acid. In addition, under conditions of low enzyme to substrate ratios, the renal medulla also produced an unusual metabolite from arachidonic acid. This metabolite was inhibited by indomethacin, and thus suggested that it was a product of the cyclooxygenase. Addition of GSH to the incubation inhibited its formation, while p-hydroxymercuri-benzoate enhanced its formation. This compound was identified by HPLC purification, uv absorption, and gas chromatography-mass spectroscopy. The compound was 9,15 dioxo,11-hydroxyprosta-5,13-dienoic acid.  相似文献   

8.
The following labeled compounds were isolated and identified after incubation of [1-14C]arachidonic acid with guinea pig lung homogenates: 12-hydroxy-5,8,10-heptadecatrienoic acid (HHT), the hemiacetal derivative of 8-(1-hydroxy-3-oxopropyl)-9,12-dihydroxy-5,10-heptadecadienoic acid (PHD), 12-hydroxy-5,8,10,14-eicosatetraenoic acid (HETE), PGE2, PGF, 11-hydroxy-5,8,12,14-eicosatetraenoic acid, and 15-hydroxy-5,8,11,13-eicosatetraenoic acid (in order of decreasing yield). Perfused guinea pig lungs released PHD (654–2304 ng), HHT (192–387 ng), HETE (66–111 ng), PGE2 (15–93 ng), and PGF (93–171 ng) following injection of 30 μg of arachidonic acid. Thus guinea pig lung homogenates as well as intact guinea pig lung converted added arachidonic acid predominantly into PHD and HHT, metabolites of the prostaglandin endoperoxide PGG2, and to a lesser extent into the classical prostaglandins PGE2 and PGF.  相似文献   

9.
We have determined the ability of UV254nm-irradiated murine lymphoma cells to adapt their NAD+ metabolism to the increased NAD+ consumption for the poly ADP-ribosylation of chromatin proteins. Two murine lymphoma sublines with differential UV-sensitivity and poly(ADP-ribose) turnover were used as a model system. The first subline, designated LY-R is UV254nm-sensitive and tumorigenic in DBA/2 mice. The second subline, LY-S is UV254nm-resistant and nontumorigenic. Following treatment of these cells with 2 mM benzamide, an inhibitor of the NAD+-utilizing enzyme poly(ADP-ribose) polymerase, NAD+ levels slowly increased up to about 160% of control levels after 3 hours. When benzamide was added to these cultures 20 min after UV254nm irradiation, a dramatic transient increase of NAD+ levels was observed within 4 min in LY-R cells and more moderately in LY-S cells. At later times after UV254nm irradiation, the NAD+ levels increased in both sublines reaching up to 200% of the concentrations prior to benzamide treatment. These results demonstrate an adaptative response of NAD+ metabolism to UV254nm irradiation. In parallel, we observed a differential repartitioning of ADP-ribosyl residues between the NAD+ and poly(ADP-ribose) pools of LY-R and LY-S cells that correlates with the differential UV sensitivity of these cells.  相似文献   

10.
Canine kidney cells (MDCK) in which [3H]arachidonic acid was esterified in the cellular lipids released increased levels of radioactive prostaglandins and arachidonic acid into the medium when cultured in the presence of benzo(a)pyrene. When MDCK cells were cultured in the presence of benzo(alpha)pyrene and 7,8-benzoflavone, this increased release was not observed. MDCK cells incubated with benzo(a)pyrene also converted exogenous arachidonic acid into prostaglandins more effectively than cells grown in its absence. 7,8-Benzoflavone inhibited this benzo(a)pyrene effect. Microsomes, prepared from benzo(alpha)pyrene-treated MDCK cells synthesized prostaglandin F2alpha from arachidonic acid more effectively than nontreated cells.  相似文献   

11.
This report focuses on the identification of the human peripheral blood mononuclear cells that do or do not produce prostaglandins (PGs) and related arachidonic acid metabolites. Our results, using two different assay systems, indicate that the monocyte/macrophage (MØ) is the major and possibly sole source of thromboxane (TXB2) and prostaglandin E2 (PGE2) among peripheral blood mononuclear cells. Adherent peripheral blood monocytes (> 95% esterase positive) produced substantial amounts of these compounds. Quantitation of products which had incorporated exogenous 14C-arachidonic acid and radioimmunoassay of adherent cell culture fluids demonstrated that the amount of TXB2 produced by these cells was appreciably greater than the amount of PGE2 produced. Additional confirmation of TXB2 synthesis was shown by abolishing the TXB2 peak on TLC and TXB2 activity detected by RIA by treating cells with a specific inhibitor of thromboxane synthetase. In contrast, non-adherent T cells failed to synthesize either PGE2 or TXB2. Non-adherent B cells (95% Ig positive) incubated with 14C-arachidonic acid produced a small peak of radioactivity co-chromatographing with TXB2, and no PGE2. All three cell populations incorporated similar amounts of 14C-arachidonic acid into hydroxy-fatty acids. We were unable to detect 6-keto-F, the hydrolysis product of prostacyclin (PGI2) in any of the cell types tested. The absence of PG synthesis among normal peripheral blood T and B cells was also noted among established human lymphoid cell lines. Neither a human T (CCRF), nor a human B-cell line (GM-130), produced PGE2 or TXB2. Three murine macrophage cell lines, P388D1, J774.2, and WHI-3 produced PGE2 and the latter TXB2 as well.  相似文献   

12.
The role of prostaglandins in exocrine pancreatic enzyme secretion was studied. The effects of three inhibitors of prostaglandin and thromboxane syntheses, were evaluated on release of amylase from dispersed rat pancreatic acinar cells. Mepacrine inhibited, while indomethacin and imidazole had no effect on basal or carbachol or cholecystokinin stimulated enzyme release. Exogenous arachidonic acid or various prostaglandins (E1, E2, F, I2), also did not affect the secretory process. Acinar cells actively incorporated radioactive arachidonic acid, principally into phospholipids (especially phosphatidylcholine), however release of the free fatty acid and subsequent synthesis of radioactive endogenous prostaglandins was not stimulated by the presence of different pancreatic stimulants. Pancreatic microsomes were found to be lacking in cyclo-oxygenase, an enzyme involved in endegenous synthesis of prostaglandins. The data suggest that prostaglandins are not involved directly in excitation-secretion coupling in the exocrine pancreas.  相似文献   

13.
Human endothelial cells in culture synthesize prostaglandins and release these products into the culture medium. The major products of arachidonic acid metabolism were identified by high pressure liquid chromatography or thin layer chromatography, and release of prostaglandins was measured by radioimmunoassays. Addition of histamine or bradykinin enhanced release of prostaglandins in both arterial and venous endothelial cells. Other vasoactive compunds including angiotensin II, vasopressin, substance P, epinephrine, norepinephrine, or isoproterenol were ineffective. Release of prostaglandins by histamine was concentration-related, and involved H1 receptors, as determined by addition of histamine antagonists. Incubation of endothelial cells with C-arachidonic acid resulted in a time-dependent uptake into cell lipids, where most of the radioactivity was incorporated into phosphatidyl choline and neutral lipids. Endothelian cells released 14C_arachidonic acid as well as 14C-prostaglandins in response to either histamine or bradykinin. The enhanced release of 14C-prostaglandins was inhibited by either indomethacin or mepacrine, but 14C-arachidonic acid release was inhibited only by mepacrine. We conclude that the vasoactive compounds, histamine and bradykinin, stimulate formation of prostaglandins in endothelial cells by the release of arachidonic acid from phospholipids of the cell membrane.  相似文献   

14.
Human synovial fibroblasts in culture respond to bradykinin with a 20-fold increment in intracellular cyclic AMP concentrations, however bradykinin does not directly activate adenylate cyclase activity in a particulate fraction derived from these cells. Bradykinin evokes a release of labeled arachidonic acid and prostaglandins E and F from synovial fibroblasts pre-labeled with 3H-arachidonic acid. Hydrocortisone inhibits the bradykinin induced increment in cyclic AMP and the release of arachidonic acid and prostaglandins E and F from synovial fibroblasts. Indomethacin, which also inhibits the cyclic AMP response to bradykinin, has no effect on the release of arachidonic acid from synovial fibroblasts. Indomethacin does, however, inhibit the quantity of prostaglandins released into the medium. These studies support the hypothesis that bradykinin does not activate human synovial fibroblast adenylate cyclase, but presumably activates a phospholipase whose products in turn result in the synthesis of prostaglandins. These and other investigations also suggest that a product(s) of the prostaglandin pathway causes the increment in cyclic AMP.  相似文献   

15.
Microstomal cells of the ciliate Tetrahymena vorax V2S can be induced to undergo cytodifferentiation to form an alternate phenotype known as the macrostomal cell; however, sublines of T. vorax exist that respond differently to methods that induce macrostomal cell formation. The phospholipid- and triacylglycerol-bound fatty acid compositions of microstomal and macrostomal cells of a high-transforming subline (designated 3-C) were determined and compared to similar data from cells of a low-transforming subline (designated Ala). Differences in fatty acid composition were found between the two phenotypes as well as between the different sublines. Some change in the distribution of radioactive acetate and lauric acid into phospholipid classes of the different subline was observed, and evidence was also obtained that indicated changes in the relative amounts of the sterol-like pentacyclic triterpenoid tetrahymanol. A limited analysis of the lipid composition of stomatin revealed the presence of small amounts of tetrahymanol, phospholipid and free fatty acid. Stomatin is the naturally produced material obtained from T. pyriformis that triggers differentiation in T. vorax. The existence of a low-transforming subline provides a powerful experimental tool for elucidating the underlying biochemical and molecular mechanisms that control cytodifferentiation in T. vorax and possibly in other eukaryotic cells.  相似文献   

16.
The ability to synthesise prostaglandins and thromboxane from 14C-labelled arachidonic acid was investigated in 11 species of fish from the Arabian Gulf. Cyclooxygenase activity was assessed in washed whole blood cells. Arachidonic acid and its metabolites were extracted and separated on silicic acid columns and thin layer chromatography (silica gel G). Total capacity to convert [14C]arachidonic acid to prostanoids varied from 1 to 35% among the 11 fish species studied. Gray shark (Chiloscyllium griseum) blood cells had the highest capacity (37±0.4%) to convert arachidonate into prostanoids and two species of catfish (Arius bilineatus and A. thalassinus) exhibited greater than 10% capacity to convert [14C]arachidonate into prostanoids. The major prostanoid synthesised by the two catfish (A. bilineatus and A thalassinus) was 6-keto PGF, a stable metabolite of prostacyclin, PGI2. In contrast, A. teunispinis synthesised thromboxane B2, a stable metabolite of thromboxane A2. Thromboxane B2 (TXB2) was the major product synthesised by all three species of shark studied (Chil. griseum, Carcharhinus plumbeus, Carch. melanopterus), with 6-keto PGF1α a minor product. Other fish studied showed a varied pattern of prostanoid synthesis. The synthesis of these prostanoids was almost completely blocked by preincubation of the whole blood cells from catfish and shark with indomethacin (0.5 μM) suggesting the involvement of cyclooxygenase-mediated prostanoid synthesis.  相似文献   

17.
We provided evidence that calcium-calmodulin plays a major role in bradykinin-induced arachidonic acid release by bovine aortic endothelial cells. In cells labeled for 16 hr with 3H-arachidonic acid, ionomycin and Ca2+-mobilizing hormones such as bradykinin, thrombin and platelet activating factor induced arachidonic acid release. However, arachidonic acid release was not induced by agents known to increase cyclic AMP (forskolin, isoproterenol) or cyclic GMP (sodium nitroprusside). Bradykinin induced the release of arachidonic acid in a dose-dependent manner (EC50 = 1.6 ± 0.7 nM). This increase was rapid, reaching a maximal value of fourfold above basal level in 15 min. In a Ca2+-free medium, bradykinin was still able to release arachidonic acid but with a lower efficiency. Quinacrine (300 μM), a blocker of PLA2, completely inhibited bradykinin-induced arachidonic acid release. The B2 bradykinin receptor antagonist HOE-140 completely inhibited bradykinin-induced arachidonic acid release. The B1-selective agonist DesArg9-bradykinin was inactive and the B1-selective antagonist [Leu8]DesArg9-bradykinin had no significant effect on bradykinin-induced arachidonic acid release. The phospholipase C inhibitor U-73122 (100 μM) decreased bradykinin-induced arachidonic acid release. The calmodulin inhibitor W-7 (50 μM) drastically reduced the bradykinin- and ionomycin-induced arachidonic acid release. Also, forskolin decreased bradykinin-induced arachidonic acid release. These results suggest that the activation of PLA2 by bradykinin in BAEC is a direct consequence of phospholipase C activation. Ca2+-calmodulin appears to be the prominent activator of PLA2 in this system. © 1996 Wiley-Liss, Inc.  相似文献   

18.
THIS report describes the biosynthesis of the naturally occurring renal prostaglandins E2 (PGE2) and F (PGF)1,2 by homogenates and slices of rabbit renal medulla, from endogenous precursors. I have confirmed that rabbit renal cortex contains little prostaglandin and cannot synthesize them from endogenous lipids3. Hamberg has reported that arachidonic acid, which is converted to PGE2 and PGF by enzymes present in ram seminal vesicles4, can be efficiently converted to PGE2 and PGF by homogenates of rabbit renal medulla3. I have now confirmed that arachidonic acid, added to such medullary homogenates, can increase the quantities of prostaglandins synthesized. There was no evidence that the major prostaglandin biosynthesized, PGE2, was further metabolized to inactive products.  相似文献   

19.
At low concentrations (i.e. 10−12–10−9 mol/l) arachidonic acid intensely stimulated both DNA synthetic and mitotic activities of hepatocytes in 4-day-old primary cultures of neonatal rat liver. This effect of arachidonate was completely suppressed by the simultaneous administration to the cultures of a high dose (i.e. 10−4 mol/l) of indomethacin. A similar, but much weaker proliferogenic activity was exerted on neonatal hepatocytes by quite low concentrations of some of the main products of arachidonic acid metabolism, namely prostaglandins A1, E1, and E2. Although these data support the possibility that arachidonate and prostaglandins are involved in the regulation of hepatocytic proliferative activation, the exact role of prostaglandins remains to be ascertained, because such agents might as well have acted by inducing intracellular surges of known mitogenic compounds, such as cAMP and cGMP.  相似文献   

20.
Early effects of various prostaglandins on the production of hexosamine-containing substances by cultured fibroblasts, which were derived from a rat carrageenin granuloma, were studied. At the stationary phase, the cells were exposed for 6 h to one of the prostaglandin A1 (PGA1), A2, B1, B2, D2, F, F, E1, E2 or arachidonic acid in various concentrations ranging from 0.01 to 10 μg/ml for all the stimuli and from 10 pg to 10 μg/ml for PGF. The activity of the cells in incorporating 3H-glucosamine into hexosamine-containing substances (acidic) glycosaminoglycans and glycoproteins) during this period was compared with that of control cells. All the stimuli tested showed more or less stimulative effect on the synthesis of hexosamine-containing substances at their specific concentrations. PGF was found to be the most potent stimulant and its stimulative effect was found significant even at the low concentration of 100 pg/ml. PGD2, F and E2 were the next potent stimuli. Their optimum dose were around 1 μg/ml but they still had significant stimulation at the concentration of 0.01 μg/ml. Effect of PGE2 was rather mild. Stimulation by PGA1, A2, B1 and B2 or arachidonic acid was seen at high dose, and its seemed to be non-specific. The results suggested that these prostaglandins such as PGF, D2, F and E2 play some important role on regulating the production of intercellular ground substances.  相似文献   

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