scholarly journals A transient increase in diacylglycerols is associated with the action of vasopressin on hepatocytes

1984 ◽  
Vol 222 (2) ◽  
pp. 535-540 ◽  
Author(s):  
B P Hughes ◽  
K A Rye ◽  
L B Pickford ◽  
G J Barritt ◽  
A H Chalmers
Keyword(s):  
Arachidonic Acid ◽  
Oleic Acid ◽  
Stearic Acid ◽  
Phospholipase C ◽  
Clostridium Perfringens ◽  
Total Concentration ◽  
Isolated Hepatocytes ◽  
Transient Increase ◽  
Rapid Hydrolysis ◽  
Hydrolysis Of

Vasopressin induced a transient increase of 50% in the total concentration of diacylglycerols (determined by g.l.c.) in isolated hepatocytes. The increase was maximal at 0.25 min, and the concentration of diacylglycerols in cells treated with vasopressin had returned to the basal value by 4 min. No change in the concentration of diacylglycerols was observed after the treatment of cells with glucagon. The dependency of this effect on the concentration of vasopressin was similar to that of the effect of the hormone on 45Ca2+ efflux measured at 0.1 mM extracellular Ca2+. Vasopressin increased the proportion of arachidonic acid and stearic acid and decreased the proportion of oleic acid present in the diacylglycerols. In hepatocytes prelabelled with [14C]arachidonic acid, vasopressin increased the amount of [14C]diacylglycerol. The effects of vasopressin on the total concentration of diacylglycerols and [14C]diacylglycerol were mimicked by an exogenous phospholipid phosphodiesterase (phospholipase C) from Clostridium perfringens. The results are consistent with the conclusion that the transient increase in diacylglycerols induced by vasopressin is caused by the rapid hydrolysis of both the phosphoinositides and one or more other phospholipids.

scholarly journals Fatty acid stimulation of membrane phosphatidylinositol hydrolysis by brain phosphatidylinositol phosphodiesterase

1979 ◽  
Vol 178 (2) ◽  
pp. 497-500 ◽  
Author(s):  
R F Irvine ◽  
A J Letcher ◽  
R M Dawson
Keyword(s):  
Arachidonic Acid ◽  
Oleic Acid ◽  
Fatty Acid ◽  
Acid Content ◽  
Microsomal Fraction ◽  
Fatty Acid Content ◽  
Membrane Bound ◽  
Liver Microsomal Fraction ◽  
Hydrolysis Of ◽  
Stimulation Of

The hydrolysis of membrane-bound phosphatidylinositol in rat liver microsomal fraction by the soluble phosphatidylinositol phosphodiesterase from rat brain was markedly stimulated by oleic acid or arachidonic acid. The stimulation did not require added calcium, although it was abolished by EDTA. Lysophosphatidylcholine also totally suppressed the stimulation. A possible role for the fatty acid content of a membrane in controlling phosphatidylinositol turnover is suggested.

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.

scholarly journals Lipidomics application to explain acute cardiotoxicity induced by doxorubicin

2019 ◽  
pp. 161-169
Keyword(s):  
Fatty Acids ◽  
Acetic Acid ◽  
Arachidonic Acid ◽  
Single Dose ◽  
Oleic Acid ◽  
Stearic Acid ◽  
Palmitic Acid ◽  
Heart Tissue ◽  
Male Rats ◽  
Experimental Protocols

Doxorubicin (DOX) induced cardio-toxicity is one of the important limiting factors for the clinical use of this drug, the exact mechanism underlying the cardiotoxicity is still under debate and different experimental protocols were used. Lipidomics technology was used in this study to investigate the underlying the cardiotoxicity is still under debate and different experimental protocols were used. Lipidomics technology was used in this study to investigate the underlying mechanism of cardiotoxicity induced by DOX. Lipidomics refers to the complete analysis of lipid profile of a cell or organism based on the principles and tools of analytical chemistry particularly mass spectrometry. This study was designed to investigate cardiotoxicity induced by doxorubicin using lipidomics technology. Method: Twelve adult male rats divided randomly into two groups, each group comprising of six rats. 1: Control group (single dose (1ml) saline intraperitoneally); 2: DOX group (20 mg/ kg single dose intraperitoneally). After anesthesia, the myocardial tissue harvested and stored in liquid nitrogen, then the metabolites will be extracted from left ventricle of the heart tissue, derivatized using boron trifluride-methanol 10% and then the metabolites identified using GC-MS. Results: The results showed that treatment with DOX produced significant (P<0.05) increase in the level of acetic acid, cholesterol, myristic acid, and stearic acid. Whereas the level of arachidonic acid, linolic acid, pentadecanoic acid, oleic acid and ricinoleic acid, decreased significantly (P<0.05) in DOX group. Lauric acid, palmitic acid, and methylcyclohexane, were found to be increased in DOX group. Conclusion: This study showed that DOX induced cardiotoxicity can be identified by lipidomics technique by measuring lipid biomarkers of cardiotoxicity in heart tissue which include the saturated fatty acids (stearic acid, acetic acid and palmitic acid), unsaturated fatty acids (arachidonic acid, linoleic acid, and oleic acid) as well as cholesterol

scholarly journals Kinetic mechanism of Clostridium perfringens phospholipase C. Hydrolysis of a thiophosphate analogue of lysophosphatidylcholine

1991 ◽  
Vol 280 (2) ◽  
pp. 407-410 ◽  
Author(s):  
P R Young ◽  
W R Snyder ◽  
R F McMahon
Keyword(s):  
Phospholipase C ◽  
Clostridium Perfringens ◽  
Kinetic Mechanism ◽  
Compound I ◽  
Nitrobenzoic Acid ◽  
Competitive Mechanism ◽  
Simple Slope ◽  
Continuous Assay ◽  
Hydrolysis Of

The hydrolysis of S-[2-(hexadecanoyloxy)ethyl]thiophosphocholine (I), an analogue of lysophosphatidylcholine, by Clostridium perfringens phospholipase C, was followed at pH 7.5, 37 degrees C and I 1.0 (maintained with KCl), in a continuous assay, by monitoring the reduction of 5,5′-dithiobis-(2-nitrobenzoic acid) at 412 nm. Simple saturation kinetics are observed with linear mixed-type slope-intercept effects for the hydrolysis of compound (I) with variable [Ca2+] at fixed concentrations of compound (I) and a simple slope effect as [compound (I)] is varied at fixed concentrations of Ca2+. These data are consistent with a simple ordered rapid-equilibrium mechanism in which Ca2+ binds to the enzyme first followed by substrate. The observed kinetic constants at pH 7.5, 37 degrees C and I 1.0 are K1 = 12.0 mM (Ca2+ dissociation), K2 = 36 microM [compound (I) dissociation] and Vmax. = 552 microM.min-1.mg-1. Alkane diammonium salts inhibit the enzyme by a non-competitive mechanism that involves binding to free enzyme, E.Ca2+ and E.Ca2+.S. The use of the simple micellarized substrate under these conditions allows the determination of kinetic and inhibition constants without complications arising from enzyme-micelle interactions.

scholarly journals Collagen stimulates [3H]inositol trisphosphate formation in indomethacin-treated human platelets

1985 ◽  
Vol 226 (3) ◽  
pp. 831-837 ◽  
Author(s):  
S P Watson ◽  
B Reep ◽  
R T McConnell ◽  
E G Lapetina
Keyword(s):  
Phospholipase C ◽  
Platelet Activation ◽  
Inositol Trisphosphate ◽  
Atp Release ◽  
Human Platelets ◽  
Lag Phase ◽  
Inositol Phospholipids ◽  
Rapid Hydrolysis ◽  
Hydrolysis Of ◽  
Indomethacin Treatment

The present study investigates the pathway of metabolism of inositol phospholipids in human platelets exposed to collagen. Platelet activation by collagen was preceded by a lag phase usually lasting 10-20 s. Formation of [3H]inositol trisphosphate (IP3) was not observed during this period, but occurred in parallel with the onset of aggregation, release of ATP and phosphorylation of a 20 000 Da and a 40 000 Da protein. Indomethacin treatment partially inhibited all of these responses. Aggregation and ATP release, but not IP3 formation, were further inhibited in indomethacin-treated platelets loaded with the fluorescent Ca2+ indicator, quin2. Under these conditions there was no detectable mobilization of Ca2+. These results demonstrate that activation of platelets by collagen is associated with rapid hydrolysis of polyphosphoinositides by phospholipase C, thereby producing IP3. This observation is discussed in relation to IP3 as a possible Ca2+-mobilizing agent.

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