scholarly journals Activity of phosphorylase in total global ischaemia in the rat heart A phosphorus-31 nuclear-magnetic-resonance study

1981 ◽  
Vol 196 (1) ◽  
pp. 171-178 ◽  
Author(s):  
I A Bailey ◽  
S R Williams ◽  
G K Radda ◽  
D G Gadian
Keyword(s):  
Inhibitory Effect ◽  
Heart Tissue ◽  
Nuclear Magnetic Resonance Study ◽  
Cytosolic Ph ◽  
Global Ischaemia ◽  
Rat Hearts ◽  
Perfused Rat Hearts ◽  
Tissue Acidosis ◽  
Good Agreement

1. The uptake and subsequent phosphorylation of deoxyglucose into perfused rat hearts was monitored by 31P n.m.r. 2. The accumulated deoxyglucose 6-phosphate provided (a) an independent method for measuring cytosolic pH in the normoxic and ischaemic heart tissue and (b) a way of studying the activity of phosphorylase during ischaemia. 3. The cytosolic pH measured from the 31P n.m.r. resonance position of deoxyglucose 6-phosphate is in good agreement under all conditions studied with that obtained previously from the Pi resonances. This eliminates any possible doubts about the use of Pi for measuring intracellular pH. 4. Deoxyglucose 6-phosphate in vitro inhibits phosphorylase b but not phosphorylase a. Its inhibitory effect on glycogenolysis during ischaemia is monitored by measuring tissue acidosis by n.m.r. In the initial stages of ischaemia phosphorylase activity is not inhibited, whereas after about 5 min approx. 50% of the activity is inhibited. These observations are interpreted in terms of the relative contributions of phosphorylase a and the AMP-dependent phosphorylase b activities during ischaemia.

Computer simulation of rat heart metabolism after adding glucose to the perfusate

1977 ◽  
Vol 232 (5) ◽  
pp. R175-R184 ◽  
Author(s):  
M. J. Achs ◽  
D. Garfinkel
Keyword(s):  
Krebs Cycle ◽  
Acid Oxidation ◽  
Allosteric Enzyme ◽  
Heart Metabolism ◽  
Rat Hearts ◽  
Cardiac Energy Metabolism ◽  
Perfused Rat Hearts ◽  
Alpha Ketoglutarate Dehydrogenase

An experiment where perfused rat hearts receiving no substrate are suddenly given glucose with insulin in the perfusate is simulated with a computer model of cardiac energy metabolism. Mitochondrial metabolism is quantitatively reorganized under cytoplasmic control, with fatty acid oxidation undergoing a two-step decrease. There is an unspanning of the Krebs cycle (different reactions going at different rates) due primarily to slowing of alpha-ketoglutarate dehydrogenase; this ends when cytoplasmic glucose reaches a new steady state. Mitochondria in vitro are known to have higher pH than their surroundings; it is found here that this also holds in situ. Under these conditions, glycolysis is coherently substrate controlled, as is phosphofructokinase, usually considered the typical example of an allosteric enzyme. Limitations on simple methods of analyzing metabolic data of this type, e.g., use of lactate/pyruvate ratios to calculate NADH/NAD ratios, are discussed. Here a large volume of enzyme and other biochemical information has been integrated into a physiologically meaningful system.

scholarly journals Regional variation and differential sensitivity of rat heart protein synthesis in vivo and in vitro

1985 ◽  
Vol 225 (2) ◽  
pp. 487-492 ◽  
Author(s):  
V R Preedy ◽  
D M Smith ◽  
N F Kearney ◽  
P H Sugden
Keyword(s):  
Protein Synthesis ◽  
Regional Variation ◽  
Subcellular Fractionation ◽  
Differential Sensitivity ◽  
Ventricular Muscle ◽  
Rat Hearts ◽  
Perfused Rat Hearts ◽  
The Right

In vivo, fractional rates of protein synthesis in atrial muscle of hearts taken from fed rats were 70% greater than in ventricular muscle. After 3 days starvation, atrial protein synthesis is inhibited, but the inhibition is less than in ventricles. A crude subcellular fractionation of the aqueous homogenates by centrifugation at 32000g showed that the supernatant and precipitate proteins were synthesized at the same rate in the ventricles. The fractional rates of protein synthesis and RNA/protein ratios in the right ventricle were 10% greater than in the left ventricle. Protein synthesis in both of these regions was inhibited equally by starvation. In vitro, rates of protein synthesis in atria and ventricles of anterogradely perfused rat hearts were stimulated by saturating insulin concentrations and were inhibited by starvation, but the effects in atria were smaller than in ventricles. Rates of protein synthesis in atria in vitro were 80-95% of rates in vivo. The heart therefore shows considerable regional variation in rates of protein synthesis in vivo and in vitro, and the sensitivity of protein synthesis in the various regions to interventions such as insulin and starvation differs.

Interaction between angiotensin II and Smad proteins in fibroblasts in failing heart and in vitro

2000 ◽  
Vol 279 (6) ◽  
pp. H3020-H3030 ◽  
Author(s):  
Jianming Hao ◽  
Baiqiu Wang ◽  
Stephen C. Jones ◽  
Davinder S. Jassal ◽  
Ian M. C. Dixon
Keyword(s):  
Angiotensin Ii ◽  
Cardiac Fibrosis ◽  
Transforming Growth Factor ◽  
Nuclear Translocation ◽  
Heart Tissue ◽  
Failing Heart ◽  
Rat Hearts ◽  
Smad Proteins ◽  
Rat Fibroblasts

Angiotensin II (angiotensin) and transforming growth factor (TGF)-β1 play an important role in cardiac fibrosis. We examined Smad proteins in 8-wk post-myocardial infarction (MI) rat hearts. AT1 blockade (losartan) attenuated the activation of TGF-β1 in target tissues. Losartan administration (8 wk, 15 mg · kg−1 · day−1) normalized total Smad 2 overexpression in infarct scar and remnant heart tissue and normalized Smad 4 in infarct scar. Phosphorylated Smad 2 (P-Smad 2) staining decreased in cytosol from failing heart vs. the control, which was normalized by losartan, suggesting augmented P-Smad 2 movement into nuclei in untreated failing hearts. Using adult primary rat fibroblasts treated with angiotensin (10−6 M), we noted rapid translocation (15 min) of P-Smad 2 into the nuclei from the cytosol. Nuclear P-Smad 2 protein level increased with angiotensin treatment, which was blocked by losartan. We conclude that angiotensin may influence total Smad 2 and 4 expression in post-MI heart failure and that angiotensin treatment is associated with rapid P-Smad 2 nuclear translocation in isolated fibroblasts. This study suggests that cross talk between angiotensin and Smad signaling is associated with fibrotic events in post-MI hearts.

scholarly journals Effects of insulin, biguanide antihyperglycaemic agents and β-adrenergic agonists on pathways of myocardial proteolysis

1990 ◽  
Vol 266 (3) ◽  
pp. 713-718 ◽  
Author(s):  
D P Thorne ◽  
T D Lockwood
Keyword(s):  
Protein Degradation ◽  
Insulin Concentration ◽  
Inhibitory Effects ◽  
Beta Agonists ◽  
Rat Hearts ◽  
Lysosomal Proteolysis ◽  
Subsequent Exposure ◽  
Perfused Rat Hearts ◽  
Perfusion Period

Pathways of bulk protein degradation controlled by insulin and isoprenaline (isoproterenol) were distinguished in Langendorff-perfused rat hearts. Proteins were biosynthetically labelled in vitro with [3H]leucine, followed by addition of 2 mM non-radioactive leucine to competitively prevent reincorporation. Rapidly degraded proteins were eliminated during a 3 h preliminary perfusion period without insulin. One third of bulk myocardial protein degradation was inhibited by isoprenaline as described previously. An insulin concentration of 5 nM maximally inhibited proteolysis, beginning within 2 min. Inhibition reached 32% within 1.25 h and 35% after 1.5 h. The minimum effective insulin concentration was approx. 10-50 pM, which caused 10-20% inhibition. Following 3 h of perfusion without insulin, the lysosomal inhibitor, chloroquine (30 microM), inhibited 38% of bulk degradation. The 35% proteolytic inhibition caused by insulin was followed by very little further inhibition on subsequent concurrent infusion of chloroquine, i.e. the inhibitory effects of insulin and chloroquine were not additive. In contrast, prior inhibition of lysosomal proteolysis by insulin or chloroquine did not prevent the subsequent additive inhibition caused by isoprenaline. Insulin and beta-agonists additively inhibited approx. two-thirds of bulk degradation. The biguanide antihyperglycaemic agent phenformin (2 microM) inhibited 35% of bulk degradation, beginning at 2 min and reaching a near maximum at approx. 1.25-1.5 h. Following inhibition of proteolysis with phenformin (20 microM), subsequent infusion of chloroquine (30 microM) produced only a slight additional inhibition. Following inhibition of 35% of degradation by 1.5 h of perfusion with insulin (5 nM), subsequent exposure to phenformin (2 microM) produced only a slight additional inhibition which did not exceed 38% of basal proteolysis. Thus insulin and phenformin both inhibit lysosomal proteolysis; however, the adrenergic-responsive pathway is distinct.

scholarly journals Studies of acidosis in the ischaemic heart by phosphorus nuclear magnetic resonance

1979 ◽  
Vol 184 (3) ◽  
pp. 547-554 ◽  
Author(s):  
P B Garlick ◽  
G K Radda ◽  
P J Seeley
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Intracellular Ph ◽  
Superconducting Magnet ◽  
Perfused Heart ◽  
Global Ischaemia ◽  
Rat Hearts ◽  
Perfused Rat Hearts ◽  
Significant Protective Effect ◽  
Nuclear Magnetic

1. Phosphorus-nuclear-magnetic-resonance measurements were made on perfused rat hearts at 37 degrees C. 2. With the improved sensitivity obtained by using a wide-bore 4.3 T superconducting magnet, spectra could be recorded in 1 min. 3. The concentrations of ATP, phosphocreatine and Pi and, from the position of the Pi resonance, the intracellular pH (pHi) were measured under a variety of conditions. 4. In a normal perfused heart pHi = 7.05 +/- 0.02 (mean +/- S.E.M. for seven hearts). 5. During global ischaemia pHi drops to 6.2 +/- 0.06 (mean +/- S.E.M.) in 13 min in a pseudoexponential decay with a rate constant of 0.25 min-1. 6. The relation between glycogen content and acidosis in ischaemia is studied in glycogen-depleted hearts. 7. Perfusion of hearts with a buffer containing 100 mM-Hepes before ischaemia gives a significant protective effect on the ischaemic myocardium. Intracellular pH and ATP and phosphocreatine concentrations decline more slowly under these conditions and metabolic recovery is observed on reperfusion after 30min of ischaemia at 37 degrees C. 8. The relation between acidosis and the export of protons is discussed and the significance of glycogenolysis in ischaemic acid production is evaluated.

Effects of relaxin on rat atrial myocytes. I. Inhibition of I(to) via PKA-dependent phosphorylation

1997 ◽  
Vol 272 (4) ◽  
pp. H1791-H1797 ◽  
Author(s):  
E. S. Piedras-Renteria ◽  
O. D. Sherwood ◽  
P. M. Best
Keyword(s):  
Potassium Current ◽  
Peptide Hormone ◽  
Inhibitory Effect ◽  
Dependent Manner ◽  
Electrophysiological Properties ◽  
Whole Cell Patch Clamp ◽  
Rat Hearts ◽  
Voltage Dependent

The peptide hormone relaxin has direct, positive inotropic and chronotropic effects on rat hearts in vivo and in vitro. Relaxin's effects on the electrophysiological properties of single quiescent atrial cells from normal rats were investigated with a whole cell patch clamp. Relaxin had a significant inhibitory effect on outward potassium currents. The outward potassium current consisted of a transient component (I(to)) and a sustained component (I(S)). The addition of 100 ng/ml of relaxin inhibited the peak I(to) in a voltage-dependent manner (74% inhibition at a membrane potential of -10 mV to 30% inhibition at +70 mV). The time to reach peak I(to) and the apparent time constant of inactivation of I(to) were increased by relaxin. Dialysis with the protein kinase A inhibitor 5-24 amide (2 microM) prevented relaxin's effects, suggesting an obligatory role for this kinase in the relaxin-dependent regulation of the potassium current.

Upregulation of CaMKIIδ during ischaemia–reperfusion is associated with reperfusion-induced arrhythmias and mechanical dysfunction of the rat heart: involvement of sarcolemmal Ca2+-cycling proteins

2012 ◽  
Vol 90 (8) ◽  
pp. 1127-1134 ◽  
Author(s):  
Adriana Adameova ◽  
Slavka Carnicka ◽  
Tomas Rajtik ◽  
Adrian Szobi ◽  
Martina Nemcekova ◽  
...  
Keyword(s):  
Sodium Calcium Exchanger ◽  
Ischaemia Reperfusion Injury ◽  
Global Ischaemia ◽  
Ischaemia Reperfusion ◽  
Rat Hearts ◽  
Perfused Rat Hearts ◽  
Dependent Protein ◽  
Chronotropic Effects ◽  
Cardiac Stunning ◽  
Contractile Recovery

Although Ca2+/calmodulin-dependent protein kinase II delta (CaMKIIδ) has been implicated in development of different phenotypes of myocardial ischaemia–reperfusion injury, its involvement in arrhythmogenesis and cardiac stunning is not sufficiently elucidated. Moreover, the mechanisms by which CaMKIIδ mediates disturbances in excitation–contraction coupling, are not exactly known. To investigate this, KN-93 (0.5 µmol/L), a CaMKII inhibitor, was administered before induction of global ischaemia and reperfusion in isolated Langendorff-perfused rat hearts. Expression of CaMKIIδ and the sarcollemal Ca2+-cycling proteins, known to be activated during reperfusion, was analyzed using immunoblotting. KN-93 reduced reperfusion-induced ectopic activity and the incidence of ventricular fibrillation. Likewise, the severity of arrhythmias was lower in KN-treated hearts. During the pre-ischaemia phase, neither inotropic nor chronotropic effects were elicited by KN-93, whereas post-ischaemic contractile recovery was significantly improved. Ischaemia–reperfusion increased the expression of CaMKIIδ and sodium–calcium exchanger (NCX1) proteins without any influence on the protein content of alpha 1c, a pore-forming subunit of L-type calcium channels (LTCCs). On the other hand, inhibition of CaMKII normalized changes in the expression of CaMKIIδ and NCX1. Taken together, CaMKIIδ seems to regulate its own turnover and to be an important component of cascade integrating NCX1, rather than LTCCs that promote ischaemia–reperfusion-induced contractile dysfunction and arrhythmias.

Inhibitory effect of Scutia buxifolia extracts, fractions, and ursolic acid on Na + , K + -ATPase activity in vitro in membranes purified from rat hearts

2016 ◽  
Vol 179 ◽  
pp. 45-54 ◽  
Author(s):  
Fabiano B. Carvalho ◽  
Aline A. Boligon ◽  
Margareth L. Athayde ◽  
Maribel A. Rubin ◽  
Juliano Ferreira ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Ursolic Acid ◽  
Inhibitory Effect ◽  
Rat Hearts

Mechanosensitive release of parathyroid hormone-related peptide from coronary endothelial cells

2002 ◽  
Vol 283 (4) ◽  
pp. H1489-H1496 ◽  
Author(s):  
Heike Degenhardt ◽  
Johanna Jansen ◽  
Rainer Schulz ◽  
Daniel Sedding ◽  
Ruediger Braun-Dullaeus ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Release Rate ◽  
Coronary Flow ◽  
Cyclic Strain ◽  
Rat Hearts ◽  
Perfused Rat Hearts ◽  
Parathyroid Hormone Related Peptide ◽  
Coronary Endothelial Cells

10.1152/ajpheart.00925. 2001.—Parathyroid hormone-related peptide (PTHrP) is expressed throughout the cardiovascular system and is able to dilate vessels. This study investigated whether mechanical forces generated by changes in regional perfusion influence PTHrP release from the coronary vascular bed. Experiments were performed in vitro on saline-perfused rat hearts or isolated coronary endothelial cells exposed to cyclic strain and in vivo in anesthetized pigs. In vitro, PTHrP release from saline-perfused rat hearts was strongly correlated with coronary flow ( r = 0.84). Increasing coronary flow from 5 to 10 ml/min increased PTHrP release from 442 ± 42 to 1,563 ± 167 pg/min. Increasing the viscosity of the perfusate did not change basal PTHrP release. Increasing flow without a concomitant increase in pressure did not lead to an increase in release rate, but reduction in pressure under flow-constant conditions reduced PTHrP release rate. Cyclic strain induced a strain-dependent release of PTHrP from endothelial cells that was inhibited by the addition of a calcium-chelating agent. In vivo, there was a net release of PTHrP in the coronary circulation and decreases in coronary flow and pressure decreased the PTHrP release rate. Bradykinin in the presence of constant pressure increased PTHrP release, probably by increasing the intracellular calcium concentration in coronary endothelial cells. In summary, mechanical forces evoked by blood flow can trigger a constant PTHrP release.

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