Phosphorylation potential, adenosine formation, and critical PO2 in stimulated rat cardiomyocytes

1997 ◽  
Vol 273 (2) ◽  
pp. H756-H766 ◽  
Author(s):  
T. Stumpe ◽  
J. Schrader
Keyword(s):  
Intracellular Ph ◽  
O2 Consumption ◽  
Energy Status ◽  
Rat Cardiomyocytes ◽  
Phosphorylation Potential ◽  
Critical Po2 ◽  
O2 Supply ◽  
The Relationship ◽  
Isolated Rat

This study investigated the relationship between O2 consumption (VO2) and energy status in isolated rat cardiomyocytes using a system in which O2 supply (PO2) was maintained constant. For this purpose, VO2, phosphocreatine, ATP, intracellular pH, and adenosine of quiescent and stimulated cardiomyocytes were measured while the ambient PO2 was clamped between 0.1 and 120 mmHg. In quiescent cardiomyocytes (VO2: 7.9 +/- 1.2 nmol.min-1.mg protein-1), the threshold below which respiration decreased (critical PO2) was 1.4 mmHg. Above this value, energy status remained constant; below 1 mmHg, both free ADP and adenosine increased. Stimulation increased VO2 threefold and shifted the critical PO2 to 10 mmHg. Above this value, free ADP and adenosine remained unchanged; between 10 and 5 mmHg. VO2 was reduced but this did not change free ADP or adenosine. These findings demonstrate that 1) under well-oxygenated conditions (PO2 > 10 mmHg), VO2 is not controlled by ADP; 2) similarly, the adenosine formation is independent of VO2; a PO2 < 5 mmHg is a prerequisite for enhanced adenosine formation; and 3) when O2 supply becomes limiting, ATP consumption is downregulated without measurable changes in energy status (hibernation).

scholarly journals Interaction of Metabolic and Respiratory Acidosis with α and β-adrenoceptor Stimulation in Rat Myocardium

2012 ◽  
Vol 117 (6) ◽  
pp. 1212-1222 ◽  
Author(s):  
Matthieu Biais ◽  
Romain Jouffroy ◽  
Aude Carillion ◽  
Sarah Feldman ◽  
Aude Jobart-Malfait ◽  
...  
Keyword(s):  
Metabolic Acidosis ◽  
Intracellular Ph ◽  
Respiratory Acidosis ◽  
Adenosine Monophosphate ◽  
Left Ventricular ◽  
Rat Myocardium ◽  
Adrenergic Stimulation ◽  
Rat Cardiomyocytes ◽  
Inotropic Effects ◽  
Isolated Rat

Background The effects of acute respiratory versus metabolic acidosis on the myocardium and their consequences on adrenoceptor stimulation remain poorly described. We compared the effects of metabolic and respiratory acidosis on inotropy and lusitropy in rat myocardium and their effects on the responses to α- and β-adrenoceptor stimulations. Methods The effects of acute respiratory and metabolic acidosis (pH 7.10) and their interactions with α and β-adrenoceptor stimulations were studied in isolated rat left ventricular papillary muscle (n=8 per group). Intracellular pH was measured using confocal microscopy and a pH-sensitive fluorophore in isolated rat cardiomyocytes. Data are mean percentages of baseline±SD. Results Respiratory acidosis induced more pronounced negative inotropic effects than metabolic acidosis did both in isotonic (45±3 versus 63±6%, P&lt;0.001) and isometric (44±5 versus 64±3%, P&lt;0.001) conditions concomitant with a greater decrease in intracellular pH (6.85±0.07 versus 7.12±0.07, P&lt;0.001). The response to α-adrenergic stimulation was not modified by respiratory or metabolic acidosis. The inotropic response to β-adrenergic stimulation was impaired only in metabolic acidosis (137±12 versus 200±33%, P&lt;0.001), but this effect was not observed with administration of forskolin or dibutiryl-cyclic adenosine monophosphate. This effect might be explained by a change in transmembrane pH gradient only observed with metabolic acidosis. The lusitropic response to β-adrenergic stimulation was not modified by respiratory or metabolic acidosis. Conclusion Acute metabolic and respiratory acidosis induce different myocardial effects related to different decreases in intracellular pH. Only metabolic acidosis impairs the positive inotropic effect of β-adrenergic stimulation.

Hepatic oxygen and lactate extraction during stagnant hypoxia

1991 ◽  
Vol 70 (1) ◽  
pp. 186-193 ◽  
Author(s):  
R. W. Samsel ◽  
D. Cherqui ◽  
A. Pietrabissa ◽  
W. M. Sanders ◽  
M. Roncella ◽  
...  
Keyword(s):  
The Body ◽  
O2 Consumption ◽  
Extraction Capacity ◽  
Blood Flows ◽  
O2 Extraction ◽  
Lactate Uptake ◽  
O2 Supply ◽  
O2 Delivery ◽  
Relationship Of ◽  
The Relationship

As O2 delivery falls, tissues must extract increasing amounts of O2 from blood to maintain a normal O2 consumption. Below a critical delivery threshold, increases in O2 extraction cannot compensate for the falling delivery, and O2 uptake falls in a supply-dependent fashion. Numerous studies have identified a critical delivery in whole animals, but the regional contributions to the critical O2 delivery are less fully understood. In the present study, we explored the limits of O2 extraction in the isolated liver, seeking to determine 1) the normal relationship between O2 consumption and delivery in the liver and 2) the relationship of hepatic lactate extraction to the drop in hepatic O2 consumption at low O2 deliveries. To answer these questions, using support dogs as a source for oxygenated metabolically stable blood, we studied eight pump-perfused canine livers. By lowering the blood flow in a model of stagnant hypoxia, we explored the relationship between O2 consumption and delivery over the entire physiological range of O2 delivery. The critical O2 delivery was 28 +/- 5 (SD) ml.kg-1.min-1; the livers extracted 68 +/- 9% of the delivered O2 before reaching supply dependence. This suggests that the liver has an O2 extraction capacity quite similar to the body as a whole and not different from other tissues that have been isolated. At high blood flows, the livers extracted approximately 10% of the lactate delivered by the blood, but the arteriovenous lactate differences were small. At low blood flows, however, the livers changed from lactate consumption to production. The O2 delivery coinciding with the dropoff in lactate extraction did not differ significantly from the critical O2 delivery. We conclude that reductions in lactate uptake by the liver do not precede the transition to O2 supply dependence.

Adenosine formation and energy status during hypoperfusion and 2-deoxyglucose infusion

1991 ◽  
Vol 260 (3) ◽  
pp. H917-H926 ◽  
Author(s):  
M. X. He ◽  
M. W. Gorman ◽  
G. D. Romig ◽  
R. A. Meyer ◽  
H. V. Sparks
Keyword(s):  
31P Nmr ◽  
Energy Charge ◽  
Energy Status ◽  
Perfused Heart ◽  
Phosphorylation Potential ◽  
Norepinephrine Infusion ◽  
Rat Hearts ◽  
The Relationship

The relationship between adenosine (Ado) formation and cytosolic energy status was studied in isolated guinea pig hearts during hypoperfusion plus norepinephrine infusion (0.6 nmol/min) and in isolated rat hearts during 2-deoxyglucose (2-DG) infusion. 31P nuclear magnetic resonance (31P-NMR) was used to measure phosphate concentrations, and both phosphorylation potential (expressed as [ATP]/[ADP][Pi]) and energy charge [expressed as (([ATP] + 1/2[ADP])/([ATP] + [ADP] + [AMP]))] were calculated as indexes of cytosolic energy status. Both progressive flow reductions and increasing length of exposure to 2-DG led to progressive decreases in energy charge and phosphorylation potential. In both cases, steady-state Ado release first increased then declined despite a continued fall in energy status. Inosine release followed a similar pattern. This biphasic pattern of Ado release vs. energy charge is similar to the pattern seen in in vitro studies of cytosolic 5'-nucleotidase, supporting the hypothesis that Ado formation in vivo is regulated by the influence of energy status on this enzyme. However, Ado release in vivo peaked at an energy charge much higher (0.997) than that observed in vitro (0.60-0.86). It is therefore probable that the inhibition of Ado formation in the perfused heart occurs via factor(s) in addition to energy charge.

scholarly journals The relationship between mitochondrial state, ATP hydrolysis, [Mg2+]i and [Ca2+]i studied in isolated rat cardiomyocytes.

1996 ◽  
Vol 496 (1) ◽  
pp. 111-128 ◽  
Author(s):  
A Leyssens ◽  
A V Nowicky ◽  
L Patterson ◽  
M Crompton ◽  
M R Duchen
Keyword(s):  
Atp Hydrolysis ◽  
Rat Cardiomyocytes ◽  
The Relationship ◽  
Isolated Rat

scholarly journals Oxygen consumption in perfused skeletal muscle. Effect of perfusion with aged, fresh and aged-rejuvenated erythrocytes on oxygen consumption, tissue metabolites and inhibition of glucose utilization by acetoacetate

1980 ◽  
Vol 190 (1) ◽  
pp. 57-64 ◽  
Author(s):  
N B Ruderman ◽  
F W Kemmer ◽  
M N Goodman ◽  
M Berger
Keyword(s):  
Skeletal Muscle ◽  
Oxygen Consumption ◽  
Glucose Utilization ◽  
Tissue Concentration ◽  
Human Erythrocytes ◽  
O2 Consumption ◽  
Energy Status ◽  
Metabolic Performance ◽  
Fast Twitch ◽  
Isolated Rat

1. O2 consumption, glucose metabolism and the energy status of skeletal muscle were compared in isolated rat hindquarters perfused with aged (21–35 days), fresh and aged-rejuvenated human erythrocytes. 2. The age of the erythrocytes did not affect O2 consumption, glucose utilization or lactate release either at rest or during exercise. The concentrations of ATP, phosphocreatine and lactate within the muscle were also unaffected by the use of aged erythrocytes. 3. Perfusion with acetoacetate did not inhibit glucose utilization; but, it caused a marked increase in the tissue concentration of citrate in the soleus, a slow-twitch red muscle, and a smaller increase in the gastrocnemius, which contains fast-twitch red and white fibres. Results were similar in hindquarters perfused with aged and aged-rejuvenated erythrocytes. 4. These findings suggest that perfusion with aged human erythrocytes does not cause major alterations in the metabolic performance of the isolated rat hindquarter.

The Relationship between Intracellular pH and Heat Sensitivity in a Thermoresistant Cell Line

1996 ◽  
Vol 145 (2) ◽  
pp. 144 ◽  
Author(s):  
F-F. Liu ◽  
M. D. Sherar ◽  
R. P. Hill
Keyword(s):  
Cell Line ◽  
Intracellular Ph ◽  
Heat Sensitivity ◽  
The Relationship

scholarly journals Adenoprotection of the heart involves phospholipase C-induced activation and translocation of PKC-ε to RACK2 in adult rat and mouse

2009 ◽  
Vol 297 (2) ◽  
pp. H718-H725 ◽  
Author(s):  
Richard A. Fenton ◽  
Satoshi Komatsu ◽  
Mitsuo Ikebe ◽  
Lynne G. Shea ◽  
James G. Dobson
Keyword(s):  
Confocal Microscopy ◽  
Phospholipase C ◽  
Adrenergic Agonist ◽  
Rat Cardiomyocytes ◽  
Scanning Confocal Microscopy ◽  
Adult Rat ◽  
Sds Page ◽  
T Tubules ◽  
Isolated Rat ◽  
Stimulation Of

Adenosine protects the heart from adrenergic overstimulation. This adenoprotection includes the direct anti-adrenergic action via adenosine A1 receptors (A1R) on the adrenergic signaling pathway. An indirect A1R-induced attenuation of adrenergic responsiveness involves the translocation of PKC-ε to t-tubules and Z-line of cardiomyocytes. We investigated with sarcomere imaging, immunocytochemistry imaging, and coimmunoprecipitation (co-IP) whether A1R activation of PKC-ε induces the kinase translocation to receptor for activated C kinase 2 (RACK2) in isolated rat and mouse hearts and whether phospholipase C (PLC) is involved. Rat cardiomyocytes were treated with the A1R agonist chlorocyclopentyladenosine (CCPA) and exposed to primary PKC-ε and RACK2 antibodies with secondaries conjugated to Cy3 and Cy5 (indodicarbocyanine), respectively. Scanning confocal microscopy showed that CCPA caused PKC-ε to reversibly colocalize with RACK2 within 3 min. Additionally, rat and mouse hearts were perfused and stimulated with CCPA or phenylisopropyladenosine to activate A1R, or with phorbol 12-myristate 13-acetate to activate PKC. RACK2 was immunoprecipitated from heart extracts and resolved with SDS-PAGE. Western blotting showed that CCPA, phenylisopropyladenosine, and phorbol 12-myristate 13-acetate in the rat heart increased the PKC-ε co-IP with RACK2 by 186, 49, and >1,000%, respectively. The A1R antagonist 8-cyclopentyl-1,3-dipropylxanthine prevented the CCPA-induced co-IP with RACK2. In mouse hearts, CCPA increased the co-IP of PKC-ε with RACK2 by 61%. With rat cardiomyocytes, the β-adrenergic agonist isoproterenol increased sarcomere shortening by 177%. CCPA reduced this response by 47%, an action inhibited by the PLC inhibitor U-73122 and 8-cyclopentyl-1,3-dipropylxanthine. In conclusion, A1R stimulation of the heart is associated with PLC-initiated PKC-ε translocation and association with RACK2.

Effects of intracellular pH on hypoxic vasoconstriction in rat lungs

1987 ◽  
Vol 63 (6) ◽  
pp. 2524-2531 ◽  
Author(s):  
B. Raffestin ◽  
I. F. McMurtry
Keyword(s):  
Intracellular Ph ◽  
Hypoxic Pulmonary Vasoconstriction ◽  
Weak Acid ◽  
Hypoxic Response ◽  
Weak Bases ◽  
Rat Lungs ◽  
Hypoxic Vasoconstriction ◽  
Ethanesulfonic Acid ◽  
Vasoactive Mediator ◽  
Isolated Rat

Isolated rat lungs perfused with physiological salt-Ficoll solutions were studied to test whether hypoxic pulmonary vasoconstriction was potentiated by increases in intracellular pH (pHi) and blunted by decreases in pHi. Whereas addition to perfusate of 5 nM phorbol myristate acetate (PMA), a stimulator of exchange of intracellular H+ for extracellular Na+, potentiated hypoxic vasoconstriction, 1 mM amiloride, an inhibitor of Na+-H+ exchange, blunted the hypoxic response. Hypoxic vasoconstriction was also potentiated by the weak bases NH4Cl (20 mM), methylamine (10 mM), and imidazole (5 mM) and was inhibited by the weak acid sodium acetate (40 mM). NH4Cl, imidazole, and acetate had the same effects on KCl-induced vasoconstriction and on the hypoxic response. Hypoxic vasoconstriction was greater in lungs perfused with N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (HEPES)-buffered solution than in those perfused with CO2/HCO3--buffered solution. Similarly, lungs perfused with CO2/HCO3--buffered solution containing 1.8 mM Cl- (NaNO3 and KNO3 substituted for NaCl and KCl) had larger hypoxic and angiotensin II pressor responses than those perfused with 122.5 mM Cl-. Because PMA, NH4Cl, methylamine, imidazole, HEPES-buffered solutions, and low-Cl- solutions can cause increases in pHi and amiloride and acetate can cause decreases in pHi, these results suggest that intracellular alkalosis and acidosis, respectively, potentiate and blunt vasoconstrictor responses to hypoxia and other stimuli in isolated rat lungs. These effects could be related to pHi-dependent changes in either the sensitivity of the arterial smooth muscle contractile machinery to Ca2+ or the release of a vasoactive mediator or modulator by some other lung cell.

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