scholarly journals Initiation of Human Parturition: XIII. Phospholipase C, Phospholipase A2, and Diacylglycerol Lipase Activities in Fetal Membranes and Decidua Vera Tissues from Early and Late Gestation1

1981 ◽  
Vol 25 (1) ◽  
pp. 103-109 ◽  
Author(s):  
Takeshi Okazaki ◽  
Norimasa Sagawa ◽  
John E. Bleasdale ◽  
Janice R. Okita ◽  
Paul C. Macdonald ◽  
...  
Keyword(s):  
Phospholipase A2 ◽  
Phospholipase C ◽  
Fetal Membranes ◽  
Diacylglycerol Lipase ◽  
Human Parturition

scholarly journals Stimulation of prostaglandin E2 synthesis by exogenous phospholipase A2 and C in rabbit kidney medulla slices

1984 ◽  
Vol 218 (1) ◽  
pp. 69-74 ◽  
Author(s):  
Y Fujimoto ◽  
N Akamatsu ◽  
A Hattori ◽  
T Fujita
Keyword(s):  
Fatty Acids ◽  
Prostaglandin E2 ◽  
Phospholipase A2 ◽  
Phospholipase C ◽  
Unsaturated Fatty Acids ◽  
Rabbit Kidney ◽  
Dependent Manner ◽  
Kidney Medulla ◽  
Diacylglycerol Lipase ◽  
Dose Dependent

We have investigated the effects of phospholipase A2 and C on the synthesis of prostaglandin E2 in rabbit kidney medulla and the release of fatty acids from the medulla slices. Exogenous phospholipase A2 [from Naja naja (Indian cobra) venom] and phospholipase C (from Clostridium welchii) stimulated prostaglandin E2 production in a dose-dependent manner. At the maximal effective concentrations (0.5 unit of phospholipase A2/ml, 2 units of phospholipase C/ml), phospholipase C increased prostaglandin E2 formation to the level observed with phospholipase A2. Phospholipase A2 enhanced the release only of unsaturated fatty acids, whereas phospholipase C stimulated the release of individual free fatty acids (C 16:0, C 18:0, C 18:1, C 18:2 and C 20:4). Moreover, p-bromophenacyl bromide inhibited phospholipase A2-stimulated prostaglandin E2 production and the release of fatty acids, but it had no influence on prostaglandin E2 formation and the release of fatty acids increased by phospholipase C, indicating that the stimulatory effect of phospholipase C is not mediated through the activation of endogenous phospholipase A2. These results suggest the presence of diacylglycerol lipase and monoacylglycerol lipase in the kidney and the importance of this pathway in prostaglandin synthesis by the kidney.

Angiotensin II stimulates phospholipases C and A2 in cultured rat mesangial cells

1987 ◽  
Vol 253 (1) ◽  
pp. C113-C120 ◽  
Author(s):  
D. Schlondorff ◽  
S. DeCandido ◽  
J. A. Satriano
Keyword(s):  
Arachidonic Acid ◽  
Angiotensin Ii ◽  
Phospholipase A2 ◽  
Phospholipase C ◽  
Mesangial Cells ◽  
Inositol Trisphosphate ◽  
Pge2 Production ◽  
Diacylglycerol Lipase ◽  
Stimulation Of ◽  
In Cells

Angiotensin II stimulates prostaglandin (PG) E2 formation in mesangial cells cultured from rat renal glomeruli. The interactions between angiotensin II and PGE2 are important in modulating glomerular function. We examined the mechanism for stimulation of PGE2 production in mesangial cells using the putative diacylglycerol-lipase inhibitor RHC 80267 and trifluoperazine (TFP), an agent interfering with Ca2+-CaM-mediated processes. Although RHC 80267 inhibited diacylglycerol-lipase activity in mesangial cells, it did not influence PGE2 production in response to either angiotensin II or A23187. In contrast, TFP (50 microM) inhibited basal PGE2 production and stimulation by angiotensin II and A23187. TFP also decreased 14C release in response to angiotensin from cells prelabeled with [14C]arachidonic acid, which was associated with inhibition of 14C loss from phosphatidylinositol. In cells prelabeled with 32P, orthophosphate angiotensin II caused a rapid hydrolysis of phosphatidylinositol 4,5-bisphospate. TFP enhanced 32P labeling of phosphatidylinositides, but did not prevent the loss of phosphatidylinositol 4,5-bisphosphate in response to angiotensin. This was verified in cells prelabeled with myo-[3H]inositol where angiotensin stimulated formation of [3H]inositol trisphosphate. TFP enhanced formation of [3H]inositol trisphosphate both under basal- and angiotensin II-stimulated conditions. Thus TFP did not inhibit phospholipase C activation by angiotensin. Angiotensin II caused marked increases in [32P]lysophospholipids, indicating activation of also phospholipase A2. This process was inhibited by TFP. Taken together, these results are consistent with stimulation of both phospholipase C and A2 by angiotensin, the latter step responsible for the release of arachidonic acid and PGE2 formation. The activation of phospholipase A2, but not that of phospholipase C, is inhibited by TFP, perhaps by interference with calmodulin-dependent steps.

EVIDENCE FOR INVOLVEMENT OF GTP-BINDING PROTEIN IN ARACKIDONIC ACID RELEASE BY PHOSPHOLIPASE A2 IN PERMEABILIZED HUMAN PLATELETS

1987 ◽  
Author(s):  
S Nakashima ◽  
T Tohmatsu ◽  
H Hattori ◽  
A Suganuma ◽  
Y Nozawa
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Phospholipase C ◽  
Binding Protein ◽  
Human Platelets ◽  
Arachidonic Acid Release ◽  
Gtp Binding Protein ◽  
Diacylglycerol Lipase ◽  
Gtp Binding ◽  
Acid Release

Platelet activation is accompanied by the active metabolism of membrane phospholipids. Phosphoinositide breakdown by phospholipase C generates second messengers; inositol trisphosphate and diacylglycerol. Recently, it is suggested that GTP-binding protein is linked to the activation of phospholipase C as is true for adenylate cyclase. Although it is known that the receptor stimulation by agonists leads to generation of arachidonic acid, its molecular mechanism has not yet been clear. However, several studies in neutrophils and mast cells using pertussis toxin, have shown the possibility that a GTP-binding protein may act as an intermediary unit component between the receptor and phospholipase A2. The present study was therefore designed to examine the effect of GTP and its analogue GTPγS on the arachidonic acid release in saponin-permeabilized human platelets. GTP or GTPγS alone caused a small but significant liberation of arachidonic acid in permeabilized cells but not in intact cells. GTP or GTPγS was found to enhance thrombin-induced [3H]arachidonic acid release in saponi n-permeabi li zed human platelets. The release of arachidonic acid has been ascribed to activity of phospholipase A2 and/or to sequential action of phospholipase C and diacylglycerol lipase. Inhibitors of phospholipase C (neomycin)/ diacylglycerol lipase (RHC 80267) pathway of arachidonate liberation did not reduce the level of the [3H]arachidonic acid release. The loss of [3H]arachidonate radioactivity from phosphatidylcholine was almost complementary to the increment of released [3H]arachidonic acid, suggesting thrombin-induced hydrolysis of phosphatidylcholine by phospholipase A2. Although phospholipase A2 usually are described as having a requirement for calcium, the effect of GTPγS was more evident at lower calcium concentrations (buffer>0.1 mM>1.0 mM). These data thus indicate that release of arachidonic acid by phospholipase A2 in saponin-treated platelets is closely linked to GTP-binding protein which may decrease the calcium requirement for phospholipase A2 activation.

scholarly journals The α1-adrenergic transduction system in hamster brown adipocytes. Release of arachidonic acid accompanies activation of phospholipase C

1988 ◽  
Vol 253 (1) ◽  
pp. 93-102 ◽  
Author(s):  
R J Schimmel
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Phospholipase C ◽  
Inositol Phosphates ◽  
Inositol Phosphate ◽  
Neutral Lipids ◽  
Receptor Activation ◽  
Ionophore A23187 ◽  
Brown Adipocytes ◽  
Diacylglycerol Lipase

Previous studies of brown adipocytes identified an increased breakdown of phosphoinositides after selective alpha 1-adrenergic-receptor activation. The present paper reports that this response, elicited with phenylephrine in the presence of propranolol and measured as the accumulation of [3H]inositol phosphates, is accompanied by increased release of [3H]arachidonic acid from cells prelabelled with [3H]arachidonic acid. Differences between stimulated arachidonic acid release and formation of inositol phosphates included a requirement for extracellular Ca2+ for stimulated release of arachidonic acid but not for the formation of inositol phosphates and the preferential inhibition of inositol phosphate formation by phorbol 12-myristate 13-acetate. The release of arachidonic acid in response to phenylephrine was associated with an accumulation of [3H]arachidonic acid-labelled diacylglycerol, and this response was not dependent on extracellular Ca2+ but was partially prevented by treatment with the phorbol ester. The release of arachidonic acid was also stimulated by melittin, which increases the activity of phospholipase A2, by ionophore A23187, by lipolytic stimulation with forskolin and by exogenous phospholipase C. The arachidonic acid response to phospholipase C was completely blocked by RHC 80267, an inhibitor of diacylglycerol lipase, but this inhibitor had no effect on release stimulated with melittin or A23187 and inhibited phenylephrine-stimulated release by only 40%. The arachidonate response to forskolin was additive with the responses to either phenylephrine or exogenous phospholipase C. These data indicate that brown adipocytes are capable of releasing arachidonic acid from neutral lipids via triacylglycerol lipolysis, and from phospholipids via phospholipase A2 or by the sequential activities of phospholipase C and diacylglycerol lipase. Our findings also suggest that the action of phenylephrine to promote the liberation of arachidonic acid utilizes both of these reactions.

Stimulation of Ca(2+)-dependent exocytosis of the sperm acrosome by cAMP acting downstream of phospholipase A2

Reproduction ◽  
2000 ◽  
pp. 57-68 ◽  
Author(s):  
J Garde ◽  
ER Roldan
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Phospholipase C ◽  
Phosphodiesterase Inhibitors ◽  
Dibutyryl Camp ◽  
Camp Phosphodiesterase ◽  
Ram Sperm ◽  
Camp Formation ◽  
Stimulation Of

Spermatozoa undergo exocytosis in response to agonists that induce Ca2+ influx and, in turn, activation of phosphoinositidase C, phospholipase C, phospholipase A2, and cAMP formation. Since the role of cAMP downstream of Ca2+ influx is unknown, this study investigated whether cAMP modulates phospholipase C or phospholipase A2 using a ram sperm model stimulated with A23187 and Ca2+. Exposure to dibutyryl-cAMP, phosphodiesterase inhibitors or forskolin resulted in enhancement of exocytosis. However, the effect was not due to stimulation of phospholipase C or phospholipase A2: in spermatozoa prelabelled with [3H]palmitic acid or [14C]arachidonic acid, these reagents did not enhance [3H]diacylglycerol formation or [14C]arachidonic acid release. Spermatozoa were treated with the phospholipase A2 inhibitor aristolochic acid, and dibutyryl-cAMP to test whether cAMP acts downstream of phospholipase A2. Under these conditions, exocytosis did not occur in response to A23187 and Ca2+. However, inclusion of dibutyryl-cAMP and the phospholipase A2 metabolite lysophosphatidylcholine did result in exocytosis (at an extent similar to that seen when cells were treated with A23187/Ca2+ and without the inhibitor). Inclusion of lysophosphatidylcholine alone, without dibutyryl-cAMP, enhanced exocytosis to a lesser extent, demonstrating that cAMP requires a phospholipase A2 metabolite to stimulate the final stages of exocytosis. These results indicate that cAMP may act downstream of phospholipase A2, exerting a regulatory role in the exocytosis triggered by physiological agonists.

Activities of phospholipase A2 and diacylglycerol lipase are increased in human colorectal cancer

1995 ◽  
Vol 82 (4) ◽  
pp. 475-478 ◽  
Author(s):  
C. W. Hendrickse ◽  
S. Radley ◽  
I. A. Donovan ◽  
M. R. B. Keighley ◽  
J. P. Neoptolemos
Keyword(s):  
Colorectal Cancer ◽  
Phospholipase A2 ◽  
Human Colorectal Cancer ◽  
Diacylglycerol Lipase

scholarly journals The Progesterone Receptor in Human Term Amniochorion and Placenta Is Isoform C

Endocrinology ◽  
2006 ◽  
Vol 147 (2) ◽  
pp. 687-693 ◽  
Author(s):  
Anthony H. Taylor ◽  
Penny C. McParland ◽  
David J. Taylor ◽  
Stephen C. Bell
Keyword(s):  
Progesterone Receptor ◽  
Western Blotting ◽  
Cell Types ◽  
Specific Role ◽  
Fetal Membranes ◽  
Rt Pcr ◽  
Reproductive Tissues ◽  
Pcr Techniques ◽  
Human Parturition ◽  
Extraembryonic Tissues

The mechanism that initiates human parturition has been proposed to be functional progesterone withdrawal whereby the 116-kDa B isoform of the progesterone receptor (PR-B) switches in favor of the 94-kDa A isoform (PR-A) in reproductive tissues. Recently other PR isoforms, PR-S, PR-C, and PR-M generated from the same gene have been identified and partially characterized. Using immunohistochemical, Western blotting, and RT-PCR techniques, evidence is provided that the major PR isoform present in human term fetal membranes (amnion and chorion) and syncytiotrophoblast of the placenta is neither of the classical nuclear PR-B or PR-A isoforms but is the N terminally truncated 60-kDa PR-C isoform. Evidence is also provided that the PR-C isoform resides in the cytoplasm of the expressing cell types. Data are also presented to show that PR-B, PR-A, and PR-S isoforms are essentially absent from the amnion and chorion, whereas PR isoforms A, B, C, and S are all present in the decidua, with PR-A being the major isoform. The syncytiotrophoblast of the placenta contains the cytoplasmic PR-C isoform but not PR-A, PR-B, or PR-S. The major PR isoform in the amnion, chorion, and placenta is PR-C, suggesting that the cytoplasmic PR-C isoform has a specific role in extraembryonic tissues and may be involved in the regulation of human parturition.

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