scholarly journals Activation of phospholipase C and prostaglandin synthesis by [arginine]vasopressin in cultures

1984 ◽  
Vol 223 (3) ◽  
pp. 855-859 ◽  
Author(s):  
J Pfeilschifter ◽  
A Kurtz ◽  
C Bauer
Keyword(s):  
Arachidonic Acid ◽  
Phosphatidic Acid ◽  
Prostaglandin E2 ◽  
Phospholipase C ◽  
Arginine Vasopressin ◽  
Mesangial Cells ◽  
Significant Loss ◽  
Prostaglandin Synthesis ◽  
Phosphatidylinositol 4 ◽  
In Cells

[Arginine]vasopressin (AVP) stimulates maximal prostaglandin E2 production in cultured rat renal mesangial cells within 2 min. As early as 10s after addition of AVP (10(-6)M) a significant loss of radioactivity from phosphatidylinositol 4,5-bisphosphate but not from phosphatidylinositol 4-phosphate and phosphatidylinositol was observed in cells prelabelled with 32Pi. Cells labelled with [14C]arachidonic acid showed an increase of label in 1,2-diacylglycerol after 15 s and in phosphatidic acid after 30 s upon stimulation with AVP. Pretreatment of the cells with indomethacin (10(-5)M) did not abolish the effect of AVP on the increased labelling of phosphatidic acid.

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.

Relationship of GTP-binding proteins, phospholipase C, and PGE2 synthesis in rat glomerular mesangial cells

1989 ◽  
Vol 256 (1) ◽  
pp. F171-F178 ◽  
Author(s):  
D. Schlondorff ◽  
P. Singhal ◽  
A. Hassid ◽  
J. A. Satriano ◽  
S. DeCandido
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase C ◽  
G Protein ◽  
Binding Proteins ◽  
Mesangial Cells ◽  
Cdna Probe ◽  
Ang Ii ◽  
Glomerular Mesangial Cells ◽  
Gtp Binding Proteins ◽  
Gtp Binding

We evaluated the role of GTP-binding proteins in the activation of phospholipase C, release of arachidonic acid, and synthesis of prostaglandin (PG) E2 in response to platelet-activating factor (PAF) and angiotensin II (ANG II) in cultured rat mesangial cells. Pretreatment with pertussis toxin (PT) decreased PGE2 formation and arachidonic acid release in response to PAF and ANG II but not that to A 23187. PT pretreatment also inhibited formation of inositol trisphosphate (IP3) in response to ANG II or PAF but did not significantly alter the rise in intracellular calcium detected by fura-2. PT catalyzed ADP ribosylation of two proteins of molecular mass approximately 40 and 41 kDa. Further evidence for involvement of GTP-binding protein in phospholipase C activation was that GTP-gamma S stimulated IP3 generation. Immunoblots with antibodies directed against different inhibitory alpha subunits of GTP-binding proteins showed that the major 40-kDa PT substrate reacted with an antibody directed against a decapeptide of the G protein subunit alpha i2 that is also found in leukocytes. This was further confirmed by Northern blot that showed the existence of mRNA in mesangial cells that hybridized with a cDNA probe for G alpha i2. In addition lesser amounts of mRNA hybridized with a restriction fragment cDNA probe for G alpha i3, which corresponds to the 41-kDa substrate for PT ribosylation. These results show that phospholipase C activation by PAF and ANG II in mesangial cells involves a specific G protein, most likely G alpha i2.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Evidence from studies employing radioactively labelled fatty acids that the stimulation of flux through the diacylglycerol pool is an early action of vasopressin on hepatocytes

1987 ◽  
Vol 245 (1) ◽  
pp. 211-216 ◽  
Author(s):  
L B Pickford ◽  
A J Polverino ◽  
G J Barritt
Keyword(s):  
Fatty Acids ◽  
Arachidonic Acid ◽  
Phosphatidic Acid ◽  
Isolated Hepatocytes ◽  
Maximal Increase ◽  
Maximal Stimulation ◽  
Early Action ◽  
Palmitic Acids ◽  
Stimulation Of ◽  
In Cells

1. In isolated hepatocytes prelabelled with [14C]-arachidonic, -stearic, -linoleic, -oleic or -palmitic acids, vasopressin increased the amount of radioactivity present in diacylglycerols. The largest increase was observed in cells labelled with arachidonic or stearic acids. 2. In cells prelabelled with [14C]- or [3H]-arachidonic acid, the onset of the increase in radioactivity in diacylglycerols induced by vasopressin was slow, the increase was partly dependent on the presence of extracellular Ca2+, and was associated with an increase in radioactivity present in phosphatidic acid which was more rapid in onset. Vasopressin decreased the amount of [3H]arachidonyl-phosphatidylinositol 4,5-bisphosphate, but the magnitude of this decrease was less than 10% of the observed increase in radioactivity in [3H]arachidonyl-diacylglycerol. 3. The concentration of vasopressin which gave half-maximal increase in [14C]arachidonyl-diacylglycerol at low extracellular Ca2+ was 10-fold higher than that which gave half-maximal stimulation of 45Ca2+ efflux. Phenylephrine, but not glucagon, also increased the amount of [14C]arachidonyl-diacylglycerol. 4. It is concluded that an early action of vasopressin on the liver cell is to increase the flux of carbon from phospholipids, including the phosphoinositides, to diacylglycerols.

scholarly journals Phorbol ester inhibits arginine vasopressin activation of phospholipase C and promotes contraction of, and prostaglandin production by, cultured mesangial cells

1988 ◽  
Vol 251 (3) ◽  
pp. 907-912 ◽  
Author(s):  
D A Troyer ◽  
O F Gonzalez ◽  
J G Douglas ◽  
J I Kreisberg
Keyword(s):  
Phospholipase C ◽  
Phorbol Ester ◽  
Arginine Vasopressin ◽  
Contractile Response ◽  
Mesangial Cells ◽  
Pge2 Production ◽  
Intact Cells ◽  
Kinase C ◽  
Acid Release ◽  
Activate Protein Kinase

We have previously shown that arginine vasopressin (AVP) causes a rapid (5-10 min) contractile response in cultured mesangial cells plated onto slippery substrata such as poly(hydroxyethyl methacrylate)-coated dishes. This contraction is associated with an increase in the levels of inositol trisphosphate (InsP3), diacylglycerol and prostaglandin E2 (PGE2). We now report that agents which are known to activate protein kinase C, i.e. phorbol 12-myristate 13-acetate (PMA) and oleolylacetylglycerol (OAG), also contract mesangial cells; however, the contractile response is slow to develop (15-30 min). The inactive phorbol ester, 4 alpha -phorbol 12,13-didecanoate, did not elicit contraction. PMA and OAG did not increase InsP3 release in mesangial cells. However, pretreatment of mesangial cells with PMA inhibited the formation of InsP3. This inhibition could not be explained by a reduction in AVP binding since PMA treatment did not influence the number or affinity of [3H]AVP binding sites in intact cells. PMA alone stimulated PGE2 production in mesangial cells to a degree similar to AVP. Contrary to what was seen with InsP3, pretreatment of cells with PMA before AVP had an additive effect on arachidonic acid release and PGE2 production. Thus, there is an apparent dissociation of phospholipase C activity from that of phospholipase A2.

Microbubble-Induced Phospholipase C Activation Does not Correlate with Platelet Aggregation

1993 ◽  
Vol 69 (04) ◽  
pp. 394-396 ◽  
Author(s):  
R Malmgren ◽  
T Thorsen ◽  
A Nordvik ◽  
H Holmsen
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Phosphatidic Acid ◽  
Phospholipase C ◽  
Human Platelets ◽  
Similar Extent ◽  
Arachidonic Acid Metabolites ◽  
Acid Metabolites ◽  
Rule Out ◽  
Stimulation Of

SummaryThe effect of nitrogen-(N2-)microbubbles on platelets resembles that of common platelet agonists with respect to aggregation and secretion, but is considerably slower and is poorly inhibited by aspirin. This paper reports the effect of microbubbles on platelet phospholipase C activity in gelfiltered human platelets prelabelled with [32P]Pi ([32P]-GFP). The experiments were run in the presence of an ADP scavenging system in order to rule out effects of ADP. Stimulation of [32P]-GFP for 30 min with microbubbles caused a significant reduction in single platelets (p <0.0004) and a significant increase in 32P-activity in the phosphatidic acid (PA) fraction (p <0.02). Epinephrine potentiated the microbubble-induced reduction in single platelets (p <0.05), but did not enhance the amount of 32P in the platelet [32P]PA fraction. The 32P-radioactivity in the PI-fraction increased with time to a similar extent when [32P]-GFP was stirred for 30 min in absence of microbubbles as it did after 30 min of agonist exposure. There were no significant changes in the [32P]PIP and [32P]PIP2 fractions. Aspirin abolished the microbubble-induced increase in 32P-activity in the PA fraction, but had no significant effect on the reduction in single platelets. Aspirin had a small but significant, reducing effect on platelet aggregation induced by a combination of epinephrine and microbubbles (p <0.05). With epinephrine, however, aspirin did not completely abolish the increase in [32P]-PA. It is concluded that microbubbles alone cause platelets to aggregate by a novel mechanism that operates independent of cyclooxygenase-dependent arachidonic acid metabolites and phospholipase C activation.

scholarly journals The interaction between lipid peroxidation and prostaglandin synthesis in rabbit kidney-medulla slices

1983 ◽  
Vol 212 (1) ◽  
pp. 167-171 ◽  
Author(s):  
Y Fujimoto ◽  
H Tanioka ◽  
I Keshi ◽  
T Fujita
Keyword(s):  
Lipid Peroxidation ◽  
Ascorbic Acid ◽  
Arachidonic Acid ◽  
Prostaglandin E2 ◽  
Inhibitory Effect ◽  
Prostaglandin Synthesis ◽  
Rabbit Kidney ◽  
Kidney Medulla ◽  
Prostaglandin Endoperoxide Synthase ◽  
Generating System

Lipid peroxidation induced by ascorbic acid and Fe2+ was inhibited by mepacrine (phospholipase A2 inhibitor) and aspirin (prostaglandin cyclo-oxygenase inhibitor) in rabbit kidney-medulla slices. Moreover, ascorbic acid and Fe2+ potentiated the inhibitory effect on prostaglandin E2 formation by mepacrine, but they had no influence on prostaglandin E2 production decreased by aspirin. Lipid peroxidation induced by ascorbic acid and Fe2+ appears to be affecting the activity of prostaglandin endoperoxide synthase. These results suggest that lipid peroxidation is connected closely with the prostaglandin-generating system, and it has the potential to modulate the turnover of arachidonic acid and prostaglandin synthesis.

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.

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