scholarly journals Relation between cytosolic free Ca2+ concentration and the control of pyruvate dehydrogenase in isolated cardiac myocytes

1987 ◽  
Vol 241 (1) ◽  
pp. 145-151 ◽  
Author(s):  
R G Hansford
Keyword(s):  
Cardiac Myocytes ◽  
Pyruvate Dehydrogenase ◽  
Energy Supply ◽  
Supply And Demand ◽  
Active Form ◽  
Chelating Agent ◽  
Work Load ◽  
Ruthenium Red ◽  
Isolated Cardiac Myocytes ◽  
Physiological Values

The proportion of pyruvate dehydrogenase existing in the active form (PDHA) in suspensions of unstimulated cardiac myocytes oxidizing glucose is approx. 30%. Depolarization of the cells with concentrations of K+ above physiological values leads to an increase in the content of PDHA. Overloading of the cells with Na+ by treatment with veratridine and ouabain gives the same result. Each of these interventions is shown in experiments with Quin 2-loaded myocytes to lead to an increase in cytosolic free Ca2+ concentration ([Ca2+]c). Treatment of the cells with Ruthenium Red, an inhibitor of Ca2+ transport into mitochondria, largely prevents an increase in PDHA in response to addition of KCl or of veratridine plus ouabain. Ruthenium Red does not attenuate the increase in [Ca2+]c that occurs under these conditions. By contrast, treatment of the cells with ryanodine, an inhibitor of sarcoplasmic-reticulum Ca2+ transport and therefore of contraction, does not diminish the response of PDHA content to agents which raise [Ca2+]c; nor does loading of the cells with the Ca2+-chelating agent Quin 2, which also prevents contraction, at appropriate concentrations. It is concluded that an increase in [Ca2+]c causes an increase in PDHA content of cardiac myocytes independently of an increase in mechanical work. In the normal physiological situation the activation of dehydrogenases by Ca2+ is thought to help to maintain the balance of energy supply and demand during periods of increased work-load, which are associated with an increased myoplasmic [Ca2+]c.

scholarly journals A comparison of the regulation of pyruvate dehydrogenase in mitochondria from rat brain and liver

1975 ◽  
Vol 150 (3) ◽  
pp. 397-403 ◽  
Author(s):  
R Jope ◽  
J P Blass
Keyword(s):  
Rat Brain ◽  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase ◽  
Active Form ◽  
Energy Charge ◽  
Liver Mitochondria ◽  
Brain Mitochondria ◽  
Ruthenium Red ◽  
Rat Brain And Liver ◽  
Pyruvate Dehydrogenase Phosphatase

The total activity of pyruvate dehydrogenase in mitochondria isolated from rat brain and liver was 53.5 and 14.2nmol/min per mg of protein respectively. Pyruvate dehydrogenase in liver mitochondria incubated for 4 min at 37 degrees C with no additions was 30% in the active form and this activity increased with longer incubations until it was completely in the active form after 20 min. Brain mitochondrial pyruvate dehydrogenase activity was initially high and did not increase with addition of Mg2+ plus Ca2+ or partially purified pyruvate dehydrogenase phosphatase or with longer incubations. The proportion of pyruvate dehydrogenase in the active form in both brain and liver mitochondria changed inversely with changes in mitochondrial energy charge, whereas total pyruvate dehydrogenase did not change. The chelators citrate, isocitrate, EDTA, ethanedioxybis(ethylamine)tetra-acetic acid and Ruthenium Red each lowered pyruvate dehydrogenase activity in brain mitochondria, but only citrate and isocitrate did so in liver mitochondria. These chelators did not affect the energy charge of the mitochondria. Mg2+ plus Ca2+ reversed the pyruvate dehydrogenase inactivation in liver, but not brain, mitochondria. The regulation of the activation-inactivation of pyruvate dehydrogenase in mitochondria from rat brain and liver with respect to energy charge is similar and may be at least partially regulated by this parameter, and the effects of chelators differ in the two types of mitochondria.

scholarly journals Role of Ca2+ ions in the regulation of intramitochondrial metabolism in rat epididymal adipose tissue. Evidence against a role for Ca2+ in the activation of pyruvate dehydrogenase by insulin

1984 ◽  
Vol 218 (1) ◽  
pp. 249-260 ◽  
Author(s):  
S E Marshall ◽  
J G McCormack ◽  
R M Denton
Keyword(s):  
Adipose Tissue ◽  
Pyruvate Dehydrogenase ◽  
Isocitrate Dehydrogenase ◽  
Active Form ◽  
Ruthenium Red ◽  
Epididymal Adipose Tissue ◽  
High Concentration ◽  
Fat Cell ◽  
Mitochondrial Inner Membrane ◽  
Oxoglutarate Dehydrogenase

The sensitivity of rat epididymal-adipose-tissue pyruvate dehydrogenase phosphate phosphatase, NAD+-isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase to Ca2+ ions was studied both in mitochondrial extracts and within intact coupled mitochondria. It is concluded that all three enzymes may be activated by increases in the intramitochondrial concentration of Ca2+ and that the distribution of Ca2+ across the mitochondrial inner membrane is determined, as in rat heart mitochondria, by the relative activities of a uniporter (which transports Ca2+ into mitochondria and is inhibited by Mg2+ and Ruthenium Red) and an antiporter (which allows Ca2+ to leave mitochondria in exchange for Na+ and is inhibited by diltiazem). Previous studies with incubated fat-cell mitochondria have indicated that the increases in the amount of active non-phosphorylated pyruvate dehydrogenase in rat epididymal tissue exposed to insulin are the result of activation of pyruvate dehydrogenase phosphate phosphatase. In the present studies, no changes in the activity of the phosphatase were found in extracts of mitochondria, and thus it seemed likely that insulin altered the intramitochondrial concentration of some effector of the phosphatase. Incubation of rat epididymal adipose tissue with medium containing a high concentration of CaCl2 (5mM) was found to increase the active form of pyruvate dehydrogenase to much the same extent as insulin. However, the increases caused by high [Ca2+] in the medium were blocked by Ruthenium Red, whereas those caused by insulin were not. Moreover, whereas the increases resulting from both treatments persisted during the preparation of mitochondria and their subsequent incubation in the absence of Na+, only the increases caused by treatment of the tissue with insulin persisted when the mitochondria were incubated in the presence of Na+ under conditions where the mitochondria are largely depleted of Ca2+. It is concluded that insulin does not act by increasing the intramitochondrial concentration of Ca2+. This conclusion was supported by finding no increases in the activities of the other two Ca2+-responsive intramitochondrial enzymes (NAD+-isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase) in mitochondria prepared from insulin-treated tissue compared with controls.

Ruthenium Red Enhancement of Surface Complex Components of Isolated and in Situ Cardiac Myocytes of Syrian Hamsters

1982 ◽  
Vol 40 ◽  
pp. 134-135
Author(s):  
T. Caceci ◽  
J.M. Orenstein ◽  
S. Bloom
Keyword(s):  
Cardiac Myocytes ◽  
Ruthenium Red ◽  
Collagen Fibrils ◽  
Surface Complex ◽  
Myocardial Mechanics ◽  
Syrian Hamsters ◽  
Isolated Cardiac Myocytes ◽  
Complex Components

Fibrils of widely differing sizes have been reported in association with the sarcolemma of cardiac myocytes in situ. Elements of this surface complex include 25-50 nm-thick striated collagen fibrils, 8-10 nm-thick unbanded fibrils (UFs), and fine 4-6 nm-thick glycocalyceal fibrils. In addition, glycosaminoglycans (GAGs) have been found associated with the surface complex. SEM examination of the surface of mechanically disaggregated myocytes revealed longitudinally-oriented cable-like fibers bridging the Z-band depressions. These cables are believed to correspond to the UFs seen in TEM preparations. We are currently studying the surface complex of isolated cardiac myocytes in an attempt to clarify its role in myocardial mechanics. In order to define the elements of the surface complex of these cells, and to examine their relationships to one another, we have applied the ruthenium red (RR) method of Luft.

scholarly journals Dependence of cardiac mitochondrial pyruvate dehydrogenase activity on intramitochondrial free Ca2+ concentration

1988 ◽  
Vol 256 (2) ◽  
pp. 403-412 ◽  
Author(s):  
R Moreno-Sánchez ◽  
R G Hansford
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Concentration Gradient ◽  
Concentration Ratio ◽  
Active Form ◽  
Ruthenium Red ◽  
Transport Processes ◽  
Kinetic Properties ◽  
Mitochondrial Matrix ◽  
The Matrix ◽  
Rat Heart Mitochondria

(1) The free Ca2+ concentration of the matrix of rat heart mitochondria ([Ca2+]m) was determined from the fluorescence of internalized indo-1. The value of the Kd of indo-1-Ca2+ in the mitochondrial matrix was determined to be 95 nM, on the basis of equilibration of [Ca2+]m with the extramitochondrial free Ca2+ ([Ca2+]o) in the presence of rotenone, nigericin, valinomycin and Br-A23187. (2) [Ca2+]m responded to energization/de-energization protocols, the inhibition of Ca2+-uptake by Ruthenium Red and the potentiation of Ca2+-efflux by Na+ in a manner which was consistent with the known kinetic properties of the mitochondrial Ca2+-transport processes. (3) The concentration gradient [Ca2+]m/[Ca2+]o was found to be near unity (0.82 +/- 0.18) when mitochondria were incubated in media containing 10 mM-Na+; the additional presence of 1 mM-Mg2+ reduced the gradient to values below unity (0.26 +/- 0.03). The polyamine spermine increased the Ca2+ concentration gradient in the presence of 1 mM-Mg2+. (4) The fraction of pyruvate dehydrogenase in the active form (PDHA) was found to increase with [Ca2+]m, with a K0.5 for activation of approximately 300 nM-Ca2+. This value of the activation constant was not affected by conditions, e.g. addition of Mg2+, which changed the [Ca2+]m/[Ca2+]o concentration gradient, and the presence of different oxidizable substrates, which changed the [NADH/NAD+]m concentration ratio. Thus pyruvate dehydrogenase interconversion responds directly to changes in [Ca2+]m, as inferred in earlier work.

Review on Job Satisfaction, Intention to Leave and Corporate Entrepreneurial Characteristics in United Arab Emirates’ Construction Firms

2017 ◽  
Vol 6 (10) ◽  
pp. 105
Author(s):  
Basma Kashmoola ◽  
Fais Ahmad ◽  
Yeoh Khar Kheng
Keyword(s):  
Job Satisfaction ◽  
United Arab Emirates ◽  
Intent To Leave ◽  
Supply And Demand ◽  
Intention To Leave ◽  
Work Load ◽  
Tourism Industry ◽  
Medium Size ◽  
Construction Companies ◽  
Developed Economies

Recently construction companies and real state of SMEs sector of Dubai, reported that they have a combine shortfall of skilled staff of up to 500,000.  In addition to that, recently tourism industry of UAE, one of the most dominating service sectors also reported the severe shortage of qualified hospitality staffs. The shortage of workforce in the industry is one of the major causes of unfair distribution of work load and also an unjust compensation and reward system in the overall industry.  The supply and demand of workforces is also one of the crucial predictor factors for job satisfaction and may lead to quit their job or to migration.While examining the various factors that may affect employee’s intention to leave, many research findings confirmed that job satisfaction caused the highest variance on to leaving intention.  To get the deeper analysis of the job satisfaction and its impact on employee’s intention to leave, many researchers argued that there were many facets of job satisfaction that may cause the leaving intentions and therefore job satisfaction has been considered a variables composed of multiple factors. It is evident that there are many studies had been conducted to examine the relationship between job satisfaction and employees leaving intentions. However, not many studies on the same line have been fully addressed in small and medium size firms in UAE working setting and also most of the studies sampling strategies had focused in industries in developed economies.  Therefore, it is believed to be a gap in the literature in the context of the job satisfaction and intent to leave in SMEs.

l-Arginine ameliorates effects of ischemia and reperfusion in isolated cardiac myocytes

2003 ◽  
Vol 476 (1-2) ◽  
pp. 45-54 ◽  
Author(s):  
Adrian Au ◽  
William E. Louch ◽  
Gregory R. Ferrier ◽  
Susan E. Howlett
Keyword(s):  
Cardiac Myocytes ◽  
Ischemia And Reperfusion ◽  
Isolated Cardiac Myocytes
Sign in / Sign up

Export Citation Format

Share Document