scholarly journals Acylation of 1-alkenyl-glycerophosphocholine and 1-acyl-glycerophosphocholine in guinea pig heart

1986 ◽  
Vol 236 (2) ◽  
pp. 481-487 ◽  
Author(s):  
G Arthur ◽  
P C Choy
Keyword(s):  
Heat Treatment ◽  
Guinea Pig ◽  
Strong Evidence ◽  
Microsomal Fraction ◽  
Kinetic Studies ◽  
Guinea Pig Heart ◽  
Acyltransferase Activity ◽  
Unsaturated Acyl ◽  
Important Pathway ◽  
High Degree

The deacylation-reacylation process has been shown to be an important pathway for phospholipids to attain the desired acyl groups at the C-2 position. The acylation of 1-acyl-glycerophosphocholine (-GPC) in mammalian hearts has been well documented, but the acylation of 1-alkenyl-GPC has not been described. In this paper, we demonstrate the presence of acyl-CoA: 1-alkenyl-GPC acyltransferase for the acylation of 1-alkenyl-GPC in mammalian hearts; the highest activity is found in guinea pig heart. The guinea pig heart 1-alkenyl-GPC acyltransferase has only 10-40% of the 1-acyl-GPC acyltransferase activity, and both activities are located in the microsomal fraction. However, these two enzymes respond differently to cations, detergents and heat treatment, and the two enzymes also display different acyl specificity. Kinetic studies indicate that both reactions could not be accommodated by the same catalytic site. The results provide strong evidence that the two activities are from separate and distinct proteins. The specificity of 1-alkenyl-GPC acyltransferase for unsaturated species of acyl-CoA may play an important role in the maintenance of the high degree of unsaturated acyl groups found in guinea pig heart plasmalogens.

scholarly journals A new assay procedure for monoglyceride acyltransferase

1974 ◽  
Vol 141 (2) ◽  
pp. 407-411 ◽  
Author(s):  
Verena J. Short ◽  
David N. Brindley ◽  
Raymond Dils
Keyword(s):  
Enzyme Activity ◽  
Guinea Pig ◽  
Intestinal Mucosa ◽  
Microsomal Fraction ◽  
Assay System ◽  
Acyltransferase Activity ◽  
Palmitoyl Carnitine ◽  
Assay Procedure ◽  
Acyl Acceptors

1. A new assay system is described for monoglyceride acyltransferase (acylglycerol palmitoyltransferase, EC 2.3.1.22) in which palmitoyl-CoA is generated from palmitoyl-(-)-carnitine. 2. With the microsomal fraction from homogenates of guinea-pig intestinal mucosa, the Vmax. of this enzyme decreased with different acyl acceptors in the order 2-monopalmitoylglycerol>2-hexadecylglycerol>rac-1-monopalmitoylglycerol. 3. There were highly significant correlations between the monoglyceride acyltransferase activity as measured with these three substrates. This demonstrates that each of these substrates can be used to measure the same enzyme activity. 4. The advantages of using generated palmitoyl-CoA with 2-hexadecylglycerol and rac-1-monopalmitoylglycerol as model substrates for this enzyme are discussed.

The presence of 1-radyl-glycerophosphoethanolamine acyltransferase activity in guinea pig heart mitochondria

1987 ◽  
Vol 65 (12) ◽  
pp. 1016-1021 ◽  
Author(s):  
Gilbert Arthur ◽  
Cheryl L. Zaborniak ◽  
Patrick C. Choy
Keyword(s):  
Arachidonic Acid ◽  
Fatty Acid Composition ◽  
Fatty Acid ◽  
Guinea Pig ◽  
Acid Composition ◽  
Heart Mitochondria ◽  
Cardiac Mitochondria ◽  
Guinea Pig Heart ◽  
Acyltransferase Activity ◽  
Ethanolamine Glycerophospholipids

Ethanolamine glycerophospholipids of mammalian heart mitochondria have a high content of arachidonic acid. Since the presence of acyltransferases that acylate 1-radyl glycerophosphoethanolamine had not been reported in the organelle, it was not known whether this high arachidonate content could be attained by the deacylation–reacylation pathway. In this study we have detected the presence of acyl-CoA:1-acyl-glycerophosphoethanolamine acyltransferase and acyl-CoA:1-alkenyl-glycerophosphoethanolamine acyltransferase activities in the guinea pig heart mitochondria. Both acyltransferases were active with palmitoyl-, stearoyl-, oleoyl-, linoleoyl-, and arachidonoyl-CoAs, but the highest activities were obtained with arachidonoyl-CoA. The acyl-CoA specificities of the enzyme(s) did not reflect the fatty acid composition of the ethanolamine glycerophospholipids. The utilization of arachidonoyl-CoA by these acyltransferases in the guinea pig heart mitochondria suggests that these enzymes may play a significant role in contributing to the high arachidonate content of the ethanolamine glycerophospholipids. However, mechanisms beyond the acyl specificity of the reacylation reactions are also involved in the maintenance of the overall acyl composition of the ethanolamine glycerophospholipid in the cardiac mitochondria.

scholarly journals The acylation of lysophosphoradylglycerocholines in guinea-pig heart mitochondria

1987 ◽  
Vol 242 (1) ◽  
pp. 171-175 ◽  
Author(s):  
G Arthur ◽  
L L Page ◽  
C L Zaborniak ◽  
P C Choy
Keyword(s):  
Guinea Pig ◽  
Fatty Acyl ◽  
Heart Mitochondria ◽  
Acyl Donor ◽  
Mitochondrial Enzyme ◽  
Microsomal Enzymes ◽  
Guinea Pig Heart ◽  
Acyltransferase Activity ◽  
Equal Importance ◽  
Acyl Acceptors

The importance of the deacylation-reacylation pathway for attaining the desired fatty acid composition in microsomal phospholipids has been well established. It is not clear, however, whether this mechanism is of equal importance in mitochondria. The absence of acyltransferase activity in mammalian heart mitochondria has been reported in a number of studies. In the present study we report the presence of acyltransferase activities for lysophosphoradylglycerocholines in guinea-pig heart mitochondria. This enzyme showed properties that were considerably different from those of the microsomal enzymes. Of all the acyl-CoAs tested (C18:0, C18:1, C18:2 and C20:4) the mitochondrial enzyme utilized only linoleoyl-CoA as fatty acyl donor and utilized both 1-acyl-sn-glycero-3-phosphocholine and 1-alkenyl-sn-glycero-3-phosphocholine as fatty acyl acceptors. The presence of significant quantities of fatty acids other than linoleate at the C-2 position of mitochondrial acylglycerophosphocholines, coupled with the specificity of the enzyme for linoleoyl-CoA, suggest that, in addition to reacylation, other mechanisms play a significant role in producing the molecular composition of these phospholipids found in the mitochondria.

scholarly journals Lysophospholipase A2 activity in guinea-pig heart microsomal fractions displaying high activities with 2-acylglycerophosphocholines with linoleic and arachidonic acids

1989 ◽  
Vol 261 (2) ◽  
pp. 581-586 ◽  
Author(s):  
G Arthur
Keyword(s):  
Guinea Pig ◽  
Phospholipase A1 ◽  
Guinea Pig Heart ◽  
Mammalian Tissues ◽  
Rate Of Hydrolysis ◽  
The One ◽  
Arachidonic Acids ◽  
High Degree ◽  
Hydrolysis Of ◽  
Lysophospholipase Activity

Lysophospholipases A1 which catalyse the hydrolysis of acyl groups from 1-acylglycerophosphocholine (GPC) have been characterized in a number of mammalian tissues and do not exhibit any acyl specificity. In the present study lysophospholipase activity in guinea-pig heart microsomes (microsomal fractions) that hydrolyses 2-acyl-GPC was detected and characterized. The enzyme showed a high degree of acyl specificity. The relative rates of hydrolysis of individual 2-acyl-GPCs with different fatty acids was as follows: C18:2/C20:1/C18:1/C16:0, 14:6:1:1. When substrates were presented in pairs, the hydrolysis of each substrate by the enzyme was inhibited, but to very different extents. Of each pair of lysolipids examined (2-arachidonoyl- and 2-palmitoyl-GPC; 2-arachidonoyl- and 2-linoleoyl-GPC), the one with the expected higher rate of hydrolysis was more severely inhibited and the degree of inhibition was dependent on the concentration of the other lysolipid. The characteristics of the lysophospholipase A2 suggest the enzyme could work in concert with phospholipase A1 to release arachidonic and linoeic acids for further metabolism. The properties of lysophospholipase A2 and A1 suggest that they are different enzymes.

Mitochondrial Oxidation of p-N, N-Dimethylamino-β-Phenethylamine (DAPA)

1975 ◽  
Vol 33 ◽  
pp. 458-459
Author(s):  
W. Allen Shannon ◽  
Hannah L. Wasserkrug ◽  
andArnold M. Seligman
Keyword(s):  
Guinea Pig ◽  
Oxidase Activity ◽  
Amine Oxidase ◽  
Histochemical Demonstration ◽  
Guinea Pig Heart ◽  
Pig Kidney ◽  
Cytoplasmic Vacuoles ◽  
Liver And Kidney ◽  
Mitochondrial Oxidation ◽  
Amine Oxidase Activity

The synthesis of a new substrate, p-N,N-dimethylamino-β-phenethylamine (DAPA)3 (Fig. 1) (1,2), and the testing of it as a possible substrate for tissue amine oxidase activity have resulted in the ultracytochemical localization of enzyme oxidase activity referred to as DAPA oxidase (DAPAO). DAPA was designed with the goal of providing an amine that would yield on oxidation a stronger reducing aldehyde than does tryptamine in the histochemical demonstration of monoamine oxidase (MAO) with tetrazolium salts.Ultracytochemical preparations of guinea pig heart, liver and kidney and rat heart and liver were studied. Guinea pig kidney, known to exhibit high levels of MAO, appeared the most reactive of the tissues studied. DAPAO reaction product appears primarily in mitochondrial outer compartments and cristae (Figs. 2-4). Reaction product is also localized in endoplasmic reticulum, cytoplasmic vacuoles and nuclear envelopes (Figs. 2 and 3) and in the sarcoplasmic reticulum of heart.

INCORPORATION OF IODIDE INTO ORGANIC COMPOUNDS IN THE GUINEA PIG THYROID

1963 ◽  
Vol 43 (1) ◽  
pp. 110-118 ◽  
Author(s):  
R. Ekholm ◽  
T. Zelander ◽  
P.-S. Agrell
Keyword(s):  
Guinea Pig ◽  
Protein Binding ◽  
Organic Compounds ◽  
Guinea Pigs ◽  
Microsomal Fraction ◽  
Thyroid Tissue ◽  
Particulate Fraction ◽  
Supernatant Fraction ◽  
Hydrolysis Of

ABSTRACT Guinea pigs, kept on a iodine-sufficient diet, were injected with Na131I and the thyroids excised from 45 seconds to 5 days later. The thyroid tissue was homogenized and separated into a combined nuclear-mitochondrial-microsomal fraction and a supernatant fraction by centrifugation at 140 000 g for one hour. Protein bound 131iodine (PB131I) and free 131iodide were determined in the fractions and the PB131I was analysed for monoiodotyrosine (MIT), diiodotyrosine (DIT) and thyroxine after hydrolysis of PB131I. As early as only 20 minutes after the Na131I-injection almost 100% of the particulate fraction 131I was protein bound. In the supernatant fraction the protein binding was somewhat less rapid and PB131I values above 90% of total supernatant 131I were not found until 3 hours after the injection. In all experiments the total amount of PB131I was higher in the supernatant than in the corresponding particulate fraction. The ratio between supernatant PB131I and pellet PB131I was lower in experiments up to 3 minutes and from 2 to 5 days than in experiments of 6 minutes to 20 hours. Hydrolysis of PB131I yielded, even in the shortest experiments, both MIT and DIT. The DIT/MIT ratio was lower in the experiments up to 2 hours than in those of 3 hours and over.

Functional and autoradiographic characterization of dopamine D2-like receptors in the guinea pig heart

2002 ◽  
Vol 80 (6) ◽  
pp. 578-587 ◽  
Author(s):  
María de Jesús Gómez ◽  
Guy Rousseau ◽  
Réginald Nadeau ◽  
Roberto Berra ◽  
Gonzalo Flores ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Western Blot ◽  
Dopamine Receptors ◽  
Negative Inotropic Effect ◽  
Cyclase Activity ◽  
Inotropic Effect ◽  
Receptor Subtypes ◽  
Guinea Pig Heart ◽  
Additional Information ◽  
The Right

Dopamine receptors include the D1- (D1 and D5 subtypes) and D2-like (D2, D3, and D4 subtypes) families. D1-like receptors are positively and D2-like receptors negatively coupled to the adenylyl cyclase. Dopamine D2-like (D4 subtype) receptors have been identified in human and rat hearts. However the presence of D2 and D3 receptor subtypes is unclear. Furthermore, their role in cardiac functions is unknown. By autoradiographic studies of guinea pig hearts, we identified D3 and D4 receptors, using the selective radioligands [3H]-7-OH-DPAT and [3H]emonapride (YM-09151-2 plus raclopride). Western blot analysis confirmed D3 and D4 receptors in the right and left ventricle of the same species. Selective agonists of D3 and D4 receptors (±)-7-OH-DPAT and PD 168 077 (10–9 to 10–5 M, respectively) induced a significant negative chronotropic and inotropic effect in the isolated guinea pig heart preparation. Negative inotropic effect induced by PD 168 077 was associated with an inhibition in cyclase activity. No changes in cyclase activity were found with (±)-7-OH-DPAT. The aim of this study is to support the presence of D3 and D4 receptors in the heart. Although our results suggest that D3 and D4 receptors are functionally active in the heart, we need additional information with an antagonist and an agonist of improved potency and selectivity to understand the respective roles of D3 and D4 receptors in the cardiac functions.Key words: Dopamine receptors (D2, D3, D4 subtypes), autoradiography, Western blot, cAMP, heart.

scholarly journals Involvement of A pertussis Toxin Sensitive G-Protein in the Inhibition of Inwardly Rectifying K+Currents by Platelet-Activating Factor in Guinea-Pig Atrial Cardiomyocytes

1994 ◽  
Vol 3 (1) ◽  
pp. 45-51
Author(s):  
M. Gollasch ◽  
T. Kleppisch ◽  
D. Krautwurst ◽  
D. Lewinsohn ◽  
J. Hescheler
Keyword(s):  
Cyclic Amp ◽  
Guinea Pig ◽  
G Protein ◽  
Pertussis Toxin ◽  
Platelet Activating Factor ◽  
Resting Membrane Potential ◽  
Patch Clamp Technique ◽  
Guinea Pig Heart ◽  
Ventricular Cells ◽  
Inwardly Rectifying

Platelet-activating factor (PAF) inhibits single inwardly rectifying K+channels in guinea-pig ventricular cells. There is currently little information as to the mechanism by which these channels are modulated. The effect of PAF on quasi steady-state inwardly rectifying K+currents (presumably of the IK1type) of auricular, atrial and ventricular cardiomyocytes from guinea-pig were studied. Applying the patch-clamp technique in the whole-cell configuration, PAF (10 nM) reduced the K+currents in all three cell types. The inhibitory effect of PAF occurred within seconds and was reversible upon wash-out. It was almost completely abolished by the PAF receptor antagonist BN 50730. Intracellular infusion of atrial cells with guanine 5′-(β-thio)diphosphate (GDPS) or pretreatment of cells with pertussis toxin abolished the PAF dependent reduction of the currents. Neither extracellularly applied isoproterenol nor intracellularly applied adenosine 3′,5′-cyclic monophosphate (cyclic AMP) attenuated the PAF effect. In multicellular preparations of auricles, PAF (10 nM) induced arrhythmias. The arrhythmogenic activity was also reduced by BN 50730. The data indicate that activated PAF receptors inhibit inwardly rectifying K+currents via a pertussis toxin sensitive G-protein without involvement of a cyclic AMP-dependent step. Since IK1is a major component in stabilizing the resting membrane potential, the observed inhibition of this type of channel could play an important role in PAF dependent arrhythmogenesis in guinea-pig heart.

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