scholarly journals Phospholipase A activity in the skin. Modulators of arachidonic acid release from phosphatidylcholine

1979 ◽  
Vol 184 (2) ◽  
pp. 283-290 ◽  
Author(s):  
V A Ziboh ◽  
J T Lord
Keyword(s):  
Arachidonic Acid ◽  
Prostaglandin E2 ◽  
Specific Activity ◽  
Feedback Regulation ◽  
Phospholipase A ◽  
Particulate Fraction ◽  
Prostaglandin F2 Alpha ◽  
Low Concentrations ◽  
Freeze Dried ◽  
Hydrolysis Of

The distribution of the hydrolysis of 1-acyl-2-[1-14C]arachidonoyl-sn-glycero-3-phosphocholine and the simultaneous biosynthesis of prostaglandins by subcellular fractions from human and rat skin membrane preparations were determined. The phospholipase A2 activity was distributed among the subcellular particulate preparations with the highest specific activity in the 105000g particulate fraction. The activity was optimal at pH 7.5 in the presence of 1.0 mM-CaCl2 and was inhibited by EDTA. The hydrolysis of phosphatidylcholine by the skin 105000g particulate fraction was inhibited by cortisol and triamcinolone acetonide and it was stimulated by histamine, bradykinin, retinoic acid and cholera enterotoxin (freeze-dried Vibrio cholerae). Furthermore hydrolysis of phosphatidylcholine by the skin phospholipase A was also enhanced by low concentrations of prostaglandin E2 and prostaglandin F2 alpha. These last results suggest that the amplication of the hydrolysis of phosphatidylcholine by prostaglandin E2 and prostaglandin F2 alpha, with the consequent release of arachidonic acid (the substrate of prostaglandin synthesis) is likely a positive-feedback regulation of the arachidonic acid-prostaglandin cascade.

Prostaglandins in dysfunctional labour; evidence for altered production of prostaglandin F2 alpha

1990 ◽  
Vol 2 (5) ◽  
pp. 563 ◽  
Author(s):  
RJ Norman ◽  
K Reddi
Keyword(s):  
Arachidonic Acid ◽  
Amniotic Fluid ◽  
Prostaglandin E2 ◽  
Fetal Membranes ◽  
Clinical Validation ◽  
Prostaglandin Synthetase ◽  
Prostaglandin F2 Alpha ◽  
Alpha Production ◽  
Low Concentrations

Dysfunctional labour was studied in relation to prostaglandin concentrations in amniotic fluid and production by fetal membranes. Initial clinical validation of the model established the presence of hypokinetic labour with no evidence of obstruction to the fetal progress. Prostaglandin F2 alpha (PGF2 alpha) and 13, 14 dihydro-15-keto-prostaglandin-F2 alpha concentrations in the amniotic fluid were low despite relatively normal concentrations of prostaglandin E2. Membranes removed from patients with the condition released very low concentrations of PGF2 alpha from the amniotic side with no alteration on the choriodecidual side of the membrane. Studies of free and phospholipid-associated arachidonic acid indicated normal release of arachidonic acid in dysfunctional labour. No changes in amniotic fluid-related inhibitors and stimulators of prostaglandin synthetase were detected. It is suggested that PGF2 alpha production is impaired in dysfunctional labour and that this prostaglandin is primarily involved in the progress of labour.

scholarly journals Studies on the phospholipases of rat intestinal mucosa

1970 ◽  
Vol 118 (2) ◽  
pp. 233-239 ◽  
Author(s):  
P. V. Subbaiah ◽  
J. Ganguly
Keyword(s):  
Fatty Acid ◽  
Intestinal Mucosa ◽  
Brush Border ◽  
Specific Activity ◽  
Sodium Deoxycholate ◽  
Phospholipase A ◽  
Phospholipase B ◽  
Ester Linkage ◽  
Hydrolysis Of ◽  
Soluble Fractions

1. Subcellular distribution and characteristics of different phospholipases of rat intestinal mucosa were studied. 2. The presence of free fatty acid was necessary for the maximal hydrolysis of lecithin (phosphatidylcholine), but there was no accumulation of lysolecithin (1 or 2-acylglycerophosphorylcholine);lysolecithin accumulated when the reaction was carried out in the presence of sodium deoxycholate and at or above pH8.0. 3. The fatty acid-activated phospholipase B as well as lysolecithinase showed optimum activity at pH6.5, whereas for the phospholipase A it was about pH8.6. 4. The bulk of the phospholipase A was present in the microsomal fraction, whereas the phospholipase B and lysolecithinase activities were distributed between the microsomal and soluble fractions of the mucosal homogenate. 5. Phospholipase A was equally distributed between the brush border and brush-border-free particulate fraction, with the brush border having highest specific activity, whereas the other two activities were distributed between the brush-border-free particulate and soluble fractions. 6. Various treatments showed marked differences between the phospholipase A and phospholipase B activities, but not between phospholipase B and lysolecithinase activities. 7. By using (β[1-14C]-oleoyl) lecithin it was shown that the mucosal phospholipase A was specific for the β-ester linkage of the lecithin molecule.

Mobilization of arachidonic acid in thrombin-stimulated human platelets

1990 ◽  
Vol 68 (2) ◽  
pp. 520-527 ◽  
Author(s):  
V. G. Mahadevappa ◽  
Frank Sicilia
Keyword(s):  
Arachidonic Acid ◽  
Phosphatidic Acid ◽  
Phospholipase C ◽  
Selective Inhibition ◽  
Human Platelets ◽  
Phospholipase A ◽  
Serine Esterase ◽  
Membrane Phospholipids ◽  
Esterase Inhibitors ◽  
Hydrolysis Of

In the present work we investigated the effect of serine esterase inhibitors such as 2-nitro-4-carboxyphenyl N,N-diphenylcarbamate (NCDC) and phenylmethylsulfonyl fluoride (PMSF), as well as the effect of mepacrine on thrombin-induced mobilization of arachidonic acid (AA) in human platelets. The inhibitor NCDC (0.6 mM) completely abolished the thrombin-induced activation of phospholipase C, phospholipase A2, and transacylase enzymes, whereas the pretreatment of platelets with PMSF (2 mM) resulted in a highly selective inhibition of phospholipase A2 and transacylase activities, with no marked effect on thrombin-induced activation of phospholipase C. The thrombin-induced release of [3H]AA from phosphatidylcholine and phosphatidylinositol was reduced by 90 and 56%, respectively, in the presence of PMSF. This inhibitor also caused a parallel inhibition in the accumulation of [3H]AA (85%) with little effect on thrombin-induced formation of [3H]phosphatidic acid (5%), whereas mepacrine (0.4 mM) caused a selective inhibition of phospholipase A2 and transacylase activities with concomitant stimulation of [3H]phosphatidic acid formation in intact human platelets. These results demonstrate that NCDC and PMSF (serine esterase inhibitors) do not affect agonist-induced activation of phospholipases that mobilize arachidonic acid through a common site. Our results further demonstrate that the inhibition of [3H]AA release observed in the presence of NCDC, PMSF, and mepacrine is primarily due to their direct effects on enzyme activities, rather than due to their indirect effects through formation of complexes between inhibitors and membrane phospholipids. Based upon these results, we also conclude that the combined hydrolysis of phosphatidylcholine and phosphatidylinositol by phospholipase A2 serves as a major source for eicosanoid biosynthesis in thrombin-stimulated human platelets.Key words: deacylation, phospholipids, thrombin, platelets, phospholipase A2.

Endothelium-dependent contractions to arachidonic acid are mediated by products of cyclooxygenase

1985 ◽  
Vol 248 (4) ◽  
pp. H432-H437 ◽  
Author(s):  
V. M. Miller ◽  
P. M. Vanhoutte
Keyword(s):  
Arachidonic Acid ◽  
Prostaglandin E2 ◽  
Isometric Tension ◽  
Optimum Length ◽  
Prostaglandin F2 Alpha ◽  
Thromboxane Synthetase ◽  
High Concentrations ◽  
Endothelium Dependent Relaxation ◽  
By Products

Arachidonic acid produces endothelium-dependent relaxation in canine arteries and endothelium-dependent contraction in veins. In canine femoral arteries, the relaxation is prevented by inhibitors of cyclooxygenase. To determine the role of cyclooxygenase in the contraction evoked by arachidonic acid in the veins, rings of canine femoral and intrapulmonary veins, with and without endothelium, were suspended in organ chambers and set at their optimum length for isometric tension measurements. In rings of femoral and pulmonary vein contracted with norepinephrine, arachidonic acid produced a concentration-dependent increase in tension that was eliminated by removal of the endothelium or by treatment with the inhibitors of cyclooxygenase (indomethacin, meclofenamate, or acetylsalicyclic acid). The contractions were not prevented by inhibitors of thromboxane synthetase or prostacyclin synthetase or lipoxygenase. Pulmonary and femoral veins with or without endothelium relaxed to low, but contracted to high concentrations of prostacyclin and prostaglandin E2. Prostaglandin F2 alpha caused endothelium-independent contractions in both blood vessels. The present study suggests that the endothelium-dependent contractions to arachidonic acid observed in canine veins are mediated by prostanoids other than thromboxane and prostacyclin.

Regulation of cellulase from Ruminococcus

1972 ◽  
Vol 18 (3) ◽  
pp. 347-353 ◽  
Author(s):  
M. C. Fusee ◽  
J. M. Leatherwood
Keyword(s):  
Enzyme Activity ◽  
Cell Growth ◽  
Catabolite Repression ◽  
Specific Activity ◽  
Product Inhibition ◽  
Enzyme Synthesis ◽  
Energy Sources ◽  
Low Concentrations ◽  
Hydrolysis Of Cellulose ◽  
Hydrolysis Of

The regulation of cellulase was examined in Ruminococcus albus and R. flavefaciens. Hydrolysis of cellulose, as shown by the formation of clear zones around the colonies of bacteria grown in cellulose-agar roll tubes, was inhibited by moderate levels of cellobiose. An intermediate in the metabolism of cellobiose may be responsible for the inhibition since strains which can use either sucrose or lactose were similarly inhibited by these energy sources. The inhibition of cellulase was examined in relation to either repression of enzyme synthesis or product inhibition of the enzyme activity. There was no inhibition by cellobiose added either to the routine enzymatic assay or to assays using low concentrations of carboxymethylcellulose. A repression mechanism was indicated by the decrease in specific activity of cultures grown in higher concentrations of cellobiose. The specific activity was calculated as the enzymatic activity on carboxymethylcellulose with respect to cell growth. The mechanism of repression was not distinguished between the model proposed by Jacob and Monod and catabolite repression. The growth of R. albus cultured in cellobiose–cellulose liquid medium exhibited a diauxic pattern similar to that described by Monod.

PGE2, PGF2 alpha, 6-keto-PGF1 alpha, and TxB2 synthesis along the rabbit nephron

1987 ◽  
Vol 252 (1) ◽  
pp. F53-F59 ◽  
Author(s):  
N. Farman ◽  
P. Pradelles ◽  
J. P. Bonvalet
Keyword(s):  
Arachidonic Acid ◽  
Prostaglandin E2 ◽  
Proximal Tubule ◽  
Enzyme Immunoassay ◽  
Thick Ascending Limb ◽  
Pge2 Synthesis ◽  
Nephron Segments ◽  
Prostaglandin F2 Alpha ◽  
Collecting Tubule ◽  
Cortical Collecting Tubule

The capacity of synthesis of prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha), 6-keto-PGF1 alpha, and thromboxane (TxB2) along the rabbit nephron was determined. A sensitive enzyme immunoassay was applied to isolated nephron segments, from the glomerulus to the terminal collecting tubule. The three prostaglandins and thromboxane (PG) were measured on the same samples after incubation in the presence of arachidonic acid. In the glomerulus, PGE2 synthesis (29.4 +/- 3.3 pg X glomerulus-1 X 30 min-1) represented 60% of the sum of the four PGs. PGF2 alpha and 6-keto-PGF1 alpha represented 22 and 17%, respectively, and TxB2 1.4%. The contribution of each PG to tubular synthesis was different, since at least 90% of PG synthesis consisted of PGE2. In the medullary collecting tubule (MCT), by far the major tubular site of PG synthesis, it was 809.6 +/- 140.8 pg X mm-1 X 30 min-1 for PGE2, 17.7 +/- 7.2 for PGF2 alpha, 8.3 +/- 1.9 for 6-keto-PGF1 alpha and 0.24 +/- 0.08 for TxB2. These relative proportions were roughly respected all along the tubule. Values were much lower in the convoluted and straight portions of the proximal tubule (proximal convoluted tubule: PGE2 8.2 +/- 2.0, PGF2 alpha 0.4 +/- 0.06, 6-keto-PGF1 alpha 0.26 +/- 0.04, TxB2 0.017) and the medullary and cortical thick ascending limb of the loop. They increased regularly along the distal structures of the tubule (light portion of the cortical collecting tubule (CCT1): PGE2 228.3 +/- 20.4, PGF2 alpha 4.34 +/- 0.6, 6-keto-PGF1 alpha 1.8 +/- 0.3, TxB2 0.22 +/- 0.07).(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Synthesis of leukotriene C and other arachidonic acid metabolites by mouse pulmonary macrophages.

1982 ◽  
Vol 155 (3) ◽  
pp. 720-733 ◽  
Author(s):  
C A Rouzer ◽  
W A Scott ◽  
A L Hamill ◽  
Z A Cohn
Keyword(s):  
Arachidonic Acid ◽  
Prostaglandin E2 ◽  
Specific Activity ◽  
Thromboxane A2 ◽  
Fatty Acid Analysis ◽  
Cell Protein ◽  
Experimental Conditions ◽  
Pulmonary Macrophages ◽  
Hydroxyeicosatetraenoic Acids

Mouse resident pulmonary macrophages were subdivided into alveolar (PAM) and interstitial (PTM) populations on the basis of accessibility to pulmonary lavage, and zymosan-induced arachidonic acid (20:4) metabolism was examined in both populations labeled with [3H]20:4. Maximal phagocytic doses of unopsonized zymosan induced the specific release of 11% of phospholipid 20:4 by PTM and 4.6% by PAM. Direct fatty acid analysis of [3H]20:4-labeled PTM cultured in the presence or absence of zymosan indicated that the specific activity of the [3H]20:4 in cell phospholipid provided an accurate measure of 20:4 released by the cells, and could therefore be used to quantitate the synthesis of 20:4 metabolites by PTM in vitro. The single major 20:4 metabolite of PTM was the slow-reacting substance leukotriene C, which was synthesized in quantities of 3-4 pmol/microgram cell protein (280-370 pmol/10(6) cells), and comprised 20-25% of the released 20:4. PTM also synthesized prostaglandin E2, prostacyclin, thromboxane A2, and hydroxyeicosatetraenoic acids. In contrast, PAM produced leukotrienes D and E in addition to leukotriene C, prostaglandin E2, thromboxane A2, and hydroxyeicosatetraenoic acids. Prostacyclin formation by PAM was not observed. These studies define a set of experimental conditions for the study of 20:4 metabolism by pulmonary macrophages, and demonstrate that these cells are rich sources of LTC as well as other 20:4 oxygenated products.

Coexistence of two biochemically distinct phospholipase A2 activities in human platelet, monocyte, and neutrophil

1993 ◽  
Vol 71 (7-8) ◽  
pp. 331-339 ◽  
Author(s):  
Lisa A. Marshall ◽  
Amy Roshak
Keyword(s):  
Arachidonic Acid ◽  
Specific Activity ◽  
Human Platelet ◽  
High Specific Activity ◽  
Cell Types ◽  
Phospholipase A ◽  
Joint Fluid ◽  
Synovial Joint ◽  
Monocytic Cell ◽  
Activity Measurements

The cell-associated phospholipase A2 (PLA2) activities of the human platelet, neutrophil, and monocyte were simultaneously characterized, utilizing the biochemical differences observed between the 14 kDa (kilodalton), type II PLA2 isolated from inflammatory human synovial joint fluid (HSF) and the arachidonic acid (AA) specific, 85-kDa high molecular mass (HMM) PLA2 isolated from the cytosol of a U937 monocytic cell line. The HSF PLA2 can be distinguished from the HMM PLA2 by its resistance to acid treatment, sensitivity to a sulfhydryl reducing agent, lack of preference for the fatty acid on the sn-2 position of phospholipid substrate, and inhibition by the C-7 phosphonate–phospholipid transition-state PLA2 inhibitor. Evaluation of all three cell types revealed that HMM-like PLA2 activity was found predominantly in the cytosolic fractions, although detection in neutrophil cytosol required more concentrated preparations and the use of high specific activity [3H]AA-labeled Escherichia coli. HSF-PLA2-like activity was measured in microsomal and cytosolic fractions of all three cell types, but was found in neutrophil cytosol only after treatment with acid. Further HMM-PLA2-specific interfering agents in neutrophil cytosol were observed and exemplifies one problem in assigning the existence of this enzyme in crude broken cell preparations using activity measurements alone. The role that these two enzymes play in eicosanoid production of the respective cell types remains to be studied.Key words: phospholipase A2, arachidonic acid, neutrophil, platelet, monocyte, cytosol, microsome.

scholarly journals 5′-CMP stimulates phospholipase A-mediated hydrolysis of phosphatidylinositol in permeabilized pituitary GH3 cells

1991 ◽  
Vol 278 (3) ◽  
pp. 831-834 ◽  
Author(s):  
A B Cubitt ◽  
C N Thaw ◽  
M C Gershengorn
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase A ◽  
Gh3 Cells ◽  
Base Exchange ◽  
Rat Pituitary ◽  
Lag Period ◽  
Hydrolysis Of

We showed previously that 5′-CMP activates PtdIns-Ins base exchange and reversal PtdIns synthase in permeabilized rat pituitary GH3 cells. Here we report another effect of 5′-CMP on PtdIns metabolism in these cells. In permeabilized GH3 cells prelabelled with [3H]Ins and incubated in buffer with LiCl and a free Ca2+ concentration of 0.1 microM but without added Ins, 5′-CMP stimulated formation of glycerophospho[3H]inositol (GroP[3H]Ins) after a lag period of at least 5 min. This effect was concentration-dependent; the apparent Km was 0.30 +/- 0.02 mM. CDP and CTP stimulated GroPIns formation less effectively than did 5′-CMP, but cytidine, 2′-CMP, 3′-CMP, 5′-AMP and 5′-GMP had no effect. 5′-CMP stimulated formation of lysoPtdIns also. In permeabilized GH3 cells prelabelled with [3H]arachidonic acid, 5′-CMP stimulated release of [3H]arachidonic acid without a measurable lag period. These data show that 5′-CMP stimulates a phospholipase A activity in permeabilized GH3 cells that hydrolyses PtdIns.

Starvation decreases insulin secretion, prostaglandin E2 production and phospholipase A2 activity in rat pancreatic islets

1990 ◽  
Vol 124 (3) ◽  
pp. 455-461 ◽  
Author(s):  
M. Tadayyon ◽  
R. C. Bonney ◽  
I. C. Green
Keyword(s):  
Arachidonic Acid ◽  
Pancreatic Islets ◽  
Acid Metabolism ◽  
Secretory Response ◽  
Phospholipase A ◽  
Prostaglandin E ◽  
Arachidonic Acid Cascade ◽  
Low Concentrations ◽  
Insulin Secretory Response ◽  
Phospholipase A2 Activity

ABSTRACT Pancreatic islets, isolated from rats starved for 48 h, secreted significantly less insulin in the presence of 2 mmol glucose/l than islets of fed controls. In contrast, the insulin secretory response of islets from fed and starved rats to a challenge of 20 mmol glucose/l was similar. Concentrations of prostaglandin E2 (PGE2) in islets from starved rats incubated with 2 mmol glucose/l were significantly lower compared with those in control islets obtained from fed animals. Although glucose (20 mmol/l) stimulated PGE2 production in islets from starved and fed rats by 2·7- and 1·6-fold respectively, the concentrations achieved were the same as a consequence of the different prestimulated concentrations. Incubation with [14C]arachidonic acid of sonicated islet preparations from fed rats and separation of metabolites generated by high-pressure liquid chromatography, indicated the biosynthesis of a number of cyclo-oxygenase- and lipoxygenase-derived compounds, including 6-keto-PGF1α, PGF2α, PGE2 and 12-hydroxyeicosatetraenoic acid. Metabolism of arachidonic acid to cyclo-oxygenase-derived compounds occurred with the same efficiency, but production of lipoxygenase-derived compounds was reduced by 50% in sonicated islets from starved compared with fed rats. Activity of phospholipase A2 of islets from starved rats was significantly less than that measured in islets from fed rats, although the degree of stimulation by 20 mmol glucose/l was the same in both types of islet. These alterations in the phospholipase A2/arachidonic acid cascade may contribute to the diminished insulin secretory response of islets from starved rats to relatively low concentrations of glucose. Journal of Endocrinology (1990) 124, 455–461

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