scholarly journals Treatment of cardiac myocytes with 8-(4-chlorophenylthio)-adenosine 3′,5′-cyclic monophosphate, forskolin or cholera toxin does not stimulate cellular or heparin-releasable lipoprotein lipase activities

1990 ◽  
Vol 270 (2) ◽  
pp. 391-395 ◽  
Author(s):  
R Carroll ◽  
A Juhasz ◽  
D L Severson
Keyword(s):  
Cholera Toxin ◽  
Lipoprotein Lipase ◽  
Cardiac Myocytes ◽  
Ventricular Myocytes ◽  
Supernatant Fraction ◽  
Protein Synthesis Inhibitor ◽  
Synthesis Inhibitor ◽  
Cyclic Monophosphate ◽  
Rat Hearts ◽  
Isolated Cardiac Myocytes

Incubation of isolated cardiac myocytes with 500 microM-8-(4-chlorophenylthio)adenosine 3′,5′-cyclic monophosphate (CPT-cAMP) or 100 microM-forskolin for 2 1/2 h did not increase the heparin-induced release of lipoprotein lipase (LPL) into the medium. When LPL activity in cardiac myocytes was depleted by treatment of rats with cycloheximide (2 mg/kg; 2.5 h) and inclusion of the protein-synthesis inhibitor in the isolation solutions, incubation with CPT-cAMP or forskolin did not influence the rate of repletion of LPL activity in cells or the recovery of heparin-releasable LPL activity. Although the administration of cholera toxin (0.5 mg/kg; 16-17 h) to rats increased LPL activity in a low-speed supernatant fraction from heparin-perfused hearts, LPL activity was not increased in cardiac myocytes from cholera-toxin-treated rat hearts, and the heparin-induced release of LPL was unchanged. Incubation of cultured ventricular myocytes with 1 microgram of cholera toxin/ml or 500 microM-CPT-cAMP for 24 h did not increase cellular LPL activity or LPL released into the culture medium after a 40 min incubation with heparin. Therefore interventions that stimulate adenylate cyclase activity (forskolin, cholera toxin) or incubation with CPT-cAMP do not increase cellular LPL activity or promote the translocation of LPL to a heparin-releasable fraction in cardiac myocytes.

Diabetes reduces heparin- and phospholipase C-releasable lipoprotein lipase from cardiomyocytes

1991 ◽  
Vol 260 (3) ◽  
pp. E477-E485 ◽  
Author(s):  
J. E. Braun ◽  
D. L. Severson
Keyword(s):  
Cell Surface ◽  
Phospholipase C ◽  
Lipoprotein Lipase ◽  
Cardiac Myocytes ◽  
Myocardial Cell ◽  
Diabetic Rats ◽  
Capillary Endothelium ◽  
Rat Hearts ◽  
Isolated Cardiac Myocytes ◽  
Covalently Linked

Incubation of isolated cardiac myocytes from rat hearts with heparin or phosphatidylinositol-specific phospholipase C (PLC) resulted in the release of lipoprotein lipase (LPL) into the medium. The release of LPL by the combination of heparin and PLC was not additive, and preincubation of cardiac myocytes with heparin eliminated the release of LPL in a subsequent incubation with PLC. This evidence suggests that LPL may be bound ionically to heparan sulfate proteoglycans that are covalently linked to the cell surface of cardiac myocytes by a phosphatidylinositol-glycan membrane anchor; a second pool of LPL may also be bound to proteoglycans attached directly to the myocardial cell surface. The induction of diabetes by the administration of streptozotocin (100 mg/kg for 3-4 days) to rats resulted in a decrease in the initial cellular activity of LPL and a marked reduction in the heparin-induced secretion of LPL into the medium of cardiac myocytes. The intravenous administration of insulin (5 U for 1 h) in diabetic rats reversed the effects of diabetes on cellular and heparin-releasable LPL activities. Diabetes also reduced the PLC-induced release of LPL. The reduction in the release of LPL from diabetic cardiac myocytes could result in a decrease in functional LPL activity at the capillary endothelium of whole hearts.

scholarly journals The kinetics of transport of lactate and pyruvate into isolated cardiac myocytes from guinea pig. Kinetic evidence for the presence of a carrier distinct from that in erythrocytes and hepatocytes

1989 ◽  
Vol 264 (2) ◽  
pp. 409-418 ◽  
Author(s):  
R C Poole ◽  
A P Halestrap ◽  
S J Price ◽  
A J Levi
Keyword(s):  
Guinea Pig ◽  
Cardiac Myocytes ◽  
Ventricular Myocytes ◽  
Silicone Oil ◽  
Free Acid ◽  
Competitive Inhibitor ◽  
Isolated Cardiac Myocytes ◽  
Lactate And Pyruvate ◽  
Time Courses ◽  
Kinetics Of

1. Time courses for the uptake of L-lactate, D-lactate and pyruvate into isolated cardiac ventricular myocytes from guinea pig were determined at 11 degrees C or 0 degrees C (for pyruvate) in a citrate-based buffer by using a silicone-oil-filtration technique. These conditions enabled initial rates of transport to be measured without interference from metabolism of the substrates. 2. At a concentration of 0.5 mM, transport of all these substrates was inhibited by approx. 90% by 5 mM-alpha-cyano-4-hydroxycinnamate; at 10 mM-L-lactate a considerable portion of transport could not be inhibited. 3. Initial rates of L-lactate and pyruvate uptake in the presence of 5 mM-alpha-cyano-4-hydroxycinnamate were linearly related to the concentration of the monocarboxylate and probably represented diffusion of the free acid. The inhibitor-sensitive component of uptake obeyed Michaelis-Menten kinetics, with Km values for L-lactate and pyruvate of 2.3 and 0.066 mM respectively. 4. Pyruvate and D-lactate inhibited the transport of L-lactate, with Ki values (competitive) of 0.077 and 6.6 mM respectively; the Ki for pyruvate was very similar to its Km for transport. The Ki for alpha-cyano-4-hydroxycinnamate as a non-competitive inhibitor was 0.042 mM. 5. These results indicate that L-lactate, D-lactate and pyruvate share a common carrier in guinea-pig cardiac myocytes; the low stereoselectivity for L-lactate over D-lactate and the high affinity for pyruvate distinguish it from the carrier in erythrocytes and hepatocytes. The metabolic roles for this novel carrier in heart are discussed.

Peroxynitrite contributes to spontaneous loss of cardiac efficiency in isolated working rat hearts

1999 ◽  
Vol 276 (6) ◽  
pp. H1861-H1867 ◽  
Author(s):  
Peter Ferdinandy ◽  
Donna Panas ◽  
Richard Schulz
Keyword(s):  
Protein Synthesis ◽  
Oxygen Consumption ◽  
Contractile Function ◽  
Tca Cycle ◽  
Protein Synthesis Inhibitor ◽  
Mechanical Function ◽  
Cardiac Work ◽  
Synthesis Inhibitor ◽  
Atp Production ◽  
Rat Hearts

We examined the mechanism of the time- and protein synthesis-dependent decline in cardiac mechanical function in isolated working rat hearts. Hearts were perfused with Krebs-Henseleit buffer for 120 min in the presence or absence of the protein synthesis inhibitor cycloheximide (CX; 10 μM). Cardiac work remained stable for 60 min and then spontaneously decreased during 60–120 min of perfusion. This was accompanied by an increase in myocardial inducible nitric oxide synthase (iNOS) and xanthine oxidase (XO) activities and enhanced dityrosine formation in the perfusate, an indicator of peroxynitrite generation. CX markedly attenuated the loss in contractile function and prevented the increase in iNOS and XO activities and dityrosine level. Despite the decline in cardiac work in control hearts, the coupling between tricarboxylic acid (TCA) cycle activity and oxygen consumption remained constant in both groups. ATP, creatine phosphate, and glycogen levels were not different between control and CX groups and did not differ over 120 min of perfusion. We concluded that the delayed and spontaneous loss in myocardial mechanical function in isolated working rat hearts is 1) attenuated by CX treatment, 2) accompanied by a concomitant increase in both iNOS and XO activities and peroxynitrite generation in the heart, and 3) not dependent on a direct impairment in myocardial ATP production, myocardial oxygen consumption, or TCA cycle acetyl-CoA production but may be due to an inefficiency of the heart to utilize ATP for contractile work.

scholarly journals inhibitor 2-[(4-methylphenyl)sulfonylcarbamido]-1-(4-nitrobenzyl)pyridinium bromide (2-AP27) is a muscarinic M2 receptor antagonist

Medicina ◽  
2009 ◽  
Vol 45 (7) ◽  
pp. 516
Author(s):  
Vytenis Skeberdis ◽  
Vida Gendvilienė ◽  
Danguolė Zablockaitė ◽  
Irma Martišienė ◽  
Antanas Stankevičius
Keyword(s):  
Cardiac Myocytes ◽  
Ventricular Myocytes ◽  
Inhibitory Effect ◽  
Patch Clamp Technique ◽  
Pyridinium Bromide ◽  
K Current ◽  
Isolated Cardiac Myocytes ◽  
Series Of Experiments ◽  
Muscarinic M2 Receptors ◽  
M2 Muscarinic Receptors

Aminopyridines are known to inhibit acetylcholine-activated K+ current (IKACh) in cardiac myocytes. The aim of this study was to examine the effect of 2-aminopyridine sulfonylcarbamide derivative 2-AP27 on isoprenaline-stimulated L-type Ca2+ current (ICaL) and to identify whether 2-AP27 acts via blocking of muscarinic M2-receptors in frog cardiomyocytes. The whole-cell configuration of the patch-clamp technique was used to record ICaL in enzymatically isolated cardiac myocytes. Isoprenaline (0.1 μM), an agonist of β1-β2-adrenoreceptors, stimulated the ICaL up to 475±61% (n=4) (P<0.05) vs. control. Then, in the first series of experiments, carbachol (0.01 μM), an agonist of M2 muscarinic receptors, reduced the stimulatory effect of isoprenaline to 42±15% vs. isoprenaline alone. 2- AP27 (100 μM) alone completely abolished the inhibitory effect of carbachol on isoprenaline-stimulated ICaL, which recovered to 95±5.8% of the effect of isoprenaline. In the second series of experiments, adenosine (1 μM), an agonist of A1-adenosine receptors, reduced the stimulatory effect of isoprenaline on ICaL to 56±10% (n=3) (P<0.05). Then 2-AP27 (100 μM) applied in the presence of adenosine, had no effect on ICaL, which remained at 51±7.9% (n=3) (P<0.05) of the effect of isoprenaline. These results suggest that 2-AP27, a new derivative of 2-AP, containing 4-toluolsulfonylcarbamide instead of amino group and quaternizated nitrogen by 4-nitrobenzylbromide in pyridine ring, is acting as an antagonist of muscarinic M2 receptors in frog ventricular myocytes.

Antibodies against ADP-ATP carrier enhance Ca2+ current in isolated cardiac myocytes

1988 ◽  
Vol 255 (4) ◽  
pp. H960-H964 ◽  
Author(s):  
M. Morad ◽  
N. W. Davies ◽  
G. Ulrich ◽  
H. P. Schultheiss
Keyword(s):  
Cardiac Myocytes ◽  
Mitochondrial Membrane ◽  
Prolonged Exposure ◽  
Ventricular Myocytes ◽  
Inner Mitochondrial Membrane ◽  
Isolated Cardiac Myocytes ◽  
Rat Myocytes ◽  
Spontaneous Contractions ◽  
First Time ◽  
Isolated Rat

Antibodies previously described to inhibit specifically nucleotide transport (ADP-ATP carrier) of the inner mitochondrial membrane were found to bind specifically to the sarcolemma of the enzymatically isolated rat ventricular myocytes. In this communication, we report for the first time that a component of these antibodies enhanced the Ca2+ current in isolated cardiac myocytes and potentiated twitch tension in ventricular strips. Prolonged exposure of rat myocytes to large concentrations of antibodies caused spontaneous contractions, progressive cell deterioration, and death. Our results thus show that a component of antibodies against ADP-ATP carrier cross-reacts with cardiac sarcolemmal proteins enhancing the Ca2+ channel.

scholarly journals Short-term incubation of cardiac myocytes with isoprenaline has no effect on heparin-releasable or cellular lipoprotein lipase activity

1987 ◽  
Vol 248 (1) ◽  
pp. 289-292 ◽  
Author(s):  
D L Severson ◽  
R Carroll ◽  
A Kryski ◽  
I Ramírez
Keyword(s):  
Lipoprotein Lipase ◽  
Cardiac Myocytes ◽  
Lipase Activity ◽  
Incubation Medium ◽  
Activity Ratio ◽  
Lipoprotein Lipase Activity ◽  
Short Term ◽  
Cyclic Monophosphate

Heparin (5 units/ml) produced a rapid (5-10 min) release of lipoprotein lipase (LPL) into the incubation medium of cardiac myocytes. Preincubation of myocytes for 30 min with 0.01-10 microM-isoprenaline, 100 microM-forskolin or 500 microM-8-(4-chlorophenylthio)adenosine 3′,5′-cyclic monophosphate did not increase heparin-releasable LPL activity. Incubation with isoprenaline also did not change cellular LPL activity, even though the catecholamine did increase the phosphorylase a activity ratio.

cGMP prevents delayed relaxation at reoxygenation after brief hypoxia in isolated cardiac myocytes

1995 ◽  
Vol 268 (6) ◽  
pp. H2396-H2204 ◽  
Author(s):  
A. M. Shah ◽  
H. S. Silverman ◽  
E. J. Griffiths ◽  
H. A. Spurgeon ◽  
E. G. Lakatta
Keyword(s):  
Relaxation Time ◽  
Cardiac Myocytes ◽  
Simultaneous Measurement ◽  
Control Group ◽  
Cyclic Monophosphate ◽  
Time To Peak ◽  
Prolonged Time ◽  
Isolated Cardiac Myocytes ◽  
Rat Myocytes ◽  
Reduced Time

Previous studies in isolated cardiac myocytes suggest that impaired relaxation during reoxygenation after brief hypoxia results from abnormal Ca(2+)-myofilament interaction. Recent studies indicate that guanosine 3',5'-cyclic monophosphate (cGMP)-elevating interventions selectively enhance myocardial relaxation. We investigated the effect of 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP) on posthypoxic relaxation in single rat myocytes, with simultaneous measurement of contraction and intracellular Ca2+ (indo 1 fluorescence). In control myocytes (n = 11), reoxygenation after 10 min of hypoxia markedly prolonged time to peak shortening (+36.5 +/- 4.2%) and half-relaxation time (+75.7 +/- 11.3% cf. normoxic values; both P < 0.001) and reduced diastolic length but did not change cytosolic Ca2+. Under normoxic conditions, 50 microM 8-BrcGMP slightly reduced time to peak shortening and half-relaxation time and increased diastolic length but did not alter cytosolic Ca2+. In the presence of 8-BrcGMP, there was no posthypoxic delay in twitch relaxation nor was there a decrease in diastolic length (half-relaxation time -5.8 +/- 3.3% cf. normoxic values; P < 0.05 cf. control group; n = 11). Cytosolic Ca2+ remained unaltered. Thus, 8-BrcGMP fully prevents impaired posthypoxic relaxation in isolated cardiac myocytes, probably by altering Ca(2+)-myofilament interaction.

Lipoprotein lipase release from cardiac myocytes is increased by decavanadate but not insulin

1992 ◽  
Vol 262 (5) ◽  
pp. E663-E670 ◽  
Author(s):  
J. E. Braun ◽  
D. L. Severson
Keyword(s):  
Lipoprotein Lipase ◽  
Cardiac Myocytes ◽  
Glucose Oxidation ◽  
Vanadyl Ion ◽  
Rat Hearts ◽  
Streptozotocin Induced Diabetes ◽  
Induced Changes ◽  
Vitro Effect

Streptozotocin-induced diabetes reduced cellular lipoprotein lipase (LPL) activity in cardiac myocytes from rat hearts and decreased the heparin-induced release of LPL into the medium. This effect of diabetes was rapidly reversed by in vivo treatment with insulin (5 U iv for 1 h); administration of insulin in vivo to control rats also increased heparin-releasable LPL activity. In contrast, in vitro addition of insulin to control and diabetic myocytes did not alter either cellular or heparin-releasable LPL activities. Insulin stimulated glucose oxidation and protein synthesis in control and diabetic myocytes. Decavanadate (0.05-1 mM) or vanadyl ion (0.5 mM) enhanced the release of LPL into the medium. Heparin- and decavanadate-induced release of LPL was not additive, and heparin pretreatment reduced the subsequent release of LPL by decavanadate. Decavanadate displaced LPL bound to heparin-Sepharose and increased LPL release into the perfusate of hearts. Therefore, decavanadate can mimic heparin in its effect on LPL. The absence of a direct in vitro effect of insulin on LPL in cardiac myocytes suggests that insulin may require some other in vivo factor or that diabetes-induced changes in LPL activity are secondary to some other metabolic factor.

Free fatty acids do not release lipoprotein lipase from isolated cardiac myocytes or perfused hearts

1992 ◽  
Vol 262 (2) ◽  
pp. E216-E223 ◽  
Author(s):  
B. Rodrigues ◽  
M. Spooner ◽  
D. L. Severson
Keyword(s):  
Fatty Acids ◽  
Oleic Acid ◽  
Cell Surface ◽  
Lipoprotein Lipase ◽  
Cardiac Myocytes ◽  
Vascular Endothelium ◽  
Capillary Endothelium ◽  
Adult Rat ◽  
Isolated Cardiac Myocytes ◽  
Perfused Hearts

Lipoprotein lipase (LPL), located at the vascular endothelium, catalyzes the hydrolysis of plasma triacylglycerols to fatty acids and 2-monoacylglycerol. In the heart, LPL is synthesized in cardiac myocytes and then translocated to the vascular endothelium. We investigated whether lipolytic products could displace LPL from the cell surface of cardiac myocytes isolated from adult rat hearts. Incubation of myocytes with 0.15-0.9 mM oleic acid or 0.1 mM monoolein did not produce a significant increase in LPL activity in the medium. LPL on the cell surface of intact myocytes hydrolyzed exogenous [3H]triolein, but there was no associated increase in LPL activity measured in the medium. Perfusion of isolated hearts with heparin (5 U/ml) resulted in displacement of LPL from the capillary endothelium. Addition of 0.9 mM oleic acid to the perfusion medium did not increase perfusate LPL activity with perfused hearts from either control or fasted rats. Therefore lipolytic products do not release active LPL from binding sites at the surface of isolated cardiac myocytes or capillary endothelial cells in perfused hearts.

Sign in / Sign up

Export Citation Format

Share Document