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.

scholarly journals Regulation kinetics of Na + ‐Ca 2+ exchange current in guinea‐pig ventricular myocytes

2000 ◽  
Vol 529 (3) ◽  
pp. 611-623 ◽  
Author(s):  
Yasutada Fujioka ◽  
Koh Hiroe ◽  
Satoshi Matsuoka
Keyword(s):  
Guinea Pig ◽  
Ventricular Myocytes ◽  
Exchange Current ◽  
Kinetics Of

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.

Effects of acidosis on Na+/Ca2+ exchange and consequences for relaxation in guinea pig cardiac myocytes

1994 ◽  
Vol 267 (2) ◽  
pp. H477-H487 ◽  
Author(s):  
C. M. Terracciano ◽  
K. T. MacLeod
Keyword(s):  
Guinea Pig ◽  
Cardiac Myocytes ◽  
Intracellular Acidosis ◽  
Rapid Cooling ◽  
Inward Current ◽  
Fluorescence Transient ◽  
Isolated Cardiac Myocytes ◽  
Rate Of Decline ◽  
The Times ◽  
Exchange Activity

We investigated the effect of intracellular acidosis (imposed by NH4Cl prepulses) on the relaxation and decline in intracellular Ca2+ (using indo 1 fluorescence) of isolated cardiac myocytes from the guinea pig. Acidosis produced a decrease in contraction and a prolongation of the fluorescence transient. The rate of decline in fluorescence after a rapid-cooling contracture was slower in acidosis compared with control. The decline in fluorescence after a rapid-cooling contracture in the presence of 10 mM caffeine was greatly slowed during acidosis, suggesting that Na+/Ca2+ exchange is affected. We recorded indo 1 fluorescence and the transient inward current in voltage-clamped cells on rapid application of 10 mM caffeine under control conditions and in acidosis. The amplitude of the transient increase in fluorescence was reduced in acidosis and the decline in fluorescence slowed. The current showed no difference in amplitude in acidosis, but the time to 50% recovery was increased by 57%. When amiloride or ethylisopropylamiloride was present, no differences in the current were found between control and acidosis, and the times to 50% recovery were similar. We conclude that intracellular acidosis slows Ca2+ efflux via Na+/Ca2+ exchange because of an increase in intracellular Na+ due to enhanced Na+/H+ exchange activity.

scholarly journals Effect of 17β-oestradiol on contraction, Ca2+ current and intracellular free Ca2+ in guinea-pig isolated cardiac myocytes

1992 ◽  
Vol 106 (3) ◽  
pp. 739-745 ◽  
Author(s):  
Canwen Jiang ◽  
Philip A. Poole-Wilson ◽  
Philip M. Sarrel ◽  
Seibu Mochizuki ◽  
Peter Collins ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Cardiac Myocytes ◽  
Isolated Cardiac Myocytes

scholarly journals Characterization of the inhibition by stilbene disulphonates and phloretin of lactate and pyruvate transport into rat and guinea-pig cardiac myocytes suggests the presence of two kinetically distinct carriers in heart cells

1993 ◽  
Vol 290 (1) ◽  
pp. 249-258 ◽  
Author(s):  
X Wang ◽  
R C Poole ◽  
A P Halestrap ◽  
A J Levi
Keyword(s):  
Guinea Pig ◽  
Cardiac Myocytes ◽  
Rat Heart ◽  
Heart Cells ◽  
Perfused Heart ◽  
Maximal Inhibition ◽  
Guinea Pig Heart ◽  
Concentration Maximum ◽  
Lactate And Pyruvate ◽  
Rat Heart Cells

1. The kinetics of transport of pyruvate (Km 0.20 mM), L-lactate (Km 2.2 mM) and D-lactate (Ki 10.2 mM) into rat cardiac myocytes were studied and compared with those for guinea-pig heart cells [Poole, Halestrap, Price and Levi (1989) Biochem. J. 264, 409-418] whose equivalent values were 0.07, 2.3 and 6.6 mM respectively. Maximal rates of transport were about 5-fold higher in the rat heart cells. 2. 4,4′-Dibenzamidostilbene-2,2′-disulphonate (DBDS), a powerful inhibitor of monocarboxylate transport into erythrocytes [Poole & Halestrap (1991) Biochem. J. 275, 307-312], was found to be a potent but apparently partial inhibitor of lactate and pyruvate transport, with an apparent Ki value at 0.5 mM L-lactate of about 16 microM in both species. Maximal inhibition was 50% and 80% in rat and guinea-pig cells respectively. 3. The maximal extent of inhibition and apparent Ki values were dependent on both the substrate transported and its concentration. Maximum inhibition was less and the Ki was greater at higher substrate concentrations. 4. A variety of other stilbene disulphonates were studied which showed different Ki values and maximal extents of inhibition. 5. Phloretin was a significantly less potent inhibitor of transport into both rat (Ki 25 microM) and guinea-pig (Ki 16 microM) heart cells than into rat erythrocytes (Ki 1.4 microM). In the rat but not the guinea-pig heart cells, inhibition appeared partial (maximal inhibition 84%). 6. We demonstrate that our results can be explained by the presence of two monocarboxylate carriers in heart cells, both with Km values for L-lactate of about 2 mM and inhibited by alpha-cyano-4-hydroxycinnamate, but with different affinities for other substrates and inhibitors. One carrier is sensitive to inhibition by stilbene disulphonates and has lower Km values for pyruvate (0.05-0.10 mM) and D-lactate (5 mM), whereas the other has higher Km values for pyruvate (0.30 mM) and D-lactate (25 mM), and is relatively insensitive to stilbene disulphonates. Rat heart cells possess more of the latter carrier and guinea-pig heart cells more of the former. 7. The significance of these results for the study of lactate transport in the perfused heart is discussed.

scholarly journals The kinetics of transport of lactate and pyruvate into rat hepatocytes. Evidence for the presence of a specific carrier similar to that in erythrocytes

1988 ◽  
Vol 249 (1) ◽  
pp. 117-126 ◽  
Author(s):  
G L Edlund ◽  
A P Halestrap
Keyword(s):  
Silicone Oil ◽  
Significant Proportion ◽  
Rat Hepatocytes ◽  
Competitive Inhibitor ◽  
Acid Uptake ◽  
Lactate Transport ◽  
Diffusion Kinetic ◽  
Isolated Rat Hepatocytes ◽  
Carrier Mediated Transport ◽  
Lactate And Pyruvate

Time courses of L-lactate and pyruvate uptake into isolated rat hepatocytes were measured in a citrate-based medium to generate a pH gradient (alkaline inside), by using the silicone-oil-filtration technique at 0 degrees C to minimize metabolism. At low concentrations of lactate and pyruvate (0.5 mM), transport was inhibited by over 95% by 5 mM-alpha-cyano-4-hydroxycinnamate, whereas at higher concentrations (greater than 10 mM) a significant proportion of transport could not be inhibited. The rate of this non-inhibitable transport was linearly related to the substrate concentration, was less with pyruvate than with L-lactate, and appeared to be due to diffusion of undissociated acid. Uptake of D-lactate was not inhibited by alpha-cyano-4-hydroxycinnamate and occurred only by diffusion. Kinetic parameters for the carrier-mediated transport process were obtained after correction of the initial rates of uptake of lactate and pyruvate in the absence of 5 mM-alpha-cyano-4-hydroxycinnamate by that in the presence of inhibitor. Under the conditions used, the Km values for L-lactate and pyruvate were 2.4 and 0.6 mM respectively and the Ki for alpha-cyano-4-hydroxycinnamate as a competitive inhibitor was 0.11 mM. Km values for the transport of L-lactate and pyruvate into rat erythrocytes under similar conditions were 3.0 and 0.96 mM. The Vmax. of lactate and pyruvate transport into hepatocytes at 0 degrees C was 3 nmol/min per mg of protein. Carrier-mediated transport of 0.5 mM-L-lactate was inhibited by 0.2 mM-p-chloromercuribenzenesulphonate (greater than 90%), 0.5 mM-quercetin (80%), 0.6 mM-isobutylcarbonyl-lactyl anhydride (70%) and 0.5 mM-4,4′-di-isothiocyanostilbene-2,2′-disulphonate (50%). A similar pattern of inhibition of lactate transport is seen in erythrocytes. It is suggested that the same or a similar carrier protein exists in both tissues. The results also show that L-lactate transport into rat hepatocytes is very rapid at physiological temperatures and is unlikely to restrict the rate of its metabolism. Differences between our results and those of Fafournoux, Demigne & Remesy [(1985) J. Biol. Chem. 260, 292-299] are discussed.

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.

Sign in / Sign up

Export Citation Format

Share Document