Akt/eNOS signaling and PLN S-sulfhydration are involved in H2S-dependent cardiac effects in frog and rat

2013 ◽  
Vol 305 (4) ◽  
pp. R443-R451 ◽  
Author(s):  
Rosa Mazza ◽  
Teresa Pasqua ◽  
Maria Carmela Cerra ◽  
Tommaso Angelone ◽  
Alfonsina Gattuso
Keyword(s):  
Rat Heart ◽  
Negative Inotropic Effect ◽  
Protein S ◽  
Rana Esculenta ◽  
Frog Heart ◽  
Akt Inhibitor ◽  
Cardiac Effects ◽  
Rat Hearts ◽  
Langendorff Hearts ◽  
Biotin Switch

Hydrogen sulfide (H2S) has recently emerged as an important mediator of mammalian cardiovascular homeostasis. In nonmammalian vertebrates, little is known about the cardiac effects of H2S. This study aimed to evaluate, in the avascular heart of the frog, Rana esculenta, whether and to what extent H2S affects the cardiac performance, and what is the mechanism of action responsible for the observed effects. Results were analyzed in relation to those obtained in the rat heart, used as the mammalian model. Isolated and perfused (working and Langendorff) hearts, Western blot analysis, and modified biotin switch (S-sulfhydration) assay were used. In the frog heart, NaHS (used as H2S donor, 10−12/10−7 M) dose-dependently decreased inotropism. This effect was reduced by glibenclamide (KATP channels blocker), N G-monomethyl-l-arginine (NOS inhibitor), 1H-[1,2,4] oxadiazolo-[4,3-a]quinoxalin-1-one (guanylyl cyclase inhibitor), KT5823 (PKG inhibitor), and it was blocked by Akt1/2 (Akt inhibitor) and by detergent Triton X-100. In the rat, in addition to the classic negative inotropic effect, NaHS (10−12/10−7 M) exhibited negative lusitropism. In both frog and rat hearts, NaHS treatment induced Akt and eNOS phosphorylation and an increased cardiac protein S-sulfhydration that, in the rat heart, includes phospholamban. Our data suggest that H2S represents a phylogenetically conserved cardioactive molecule. Results obtained on the rat heart extend the role of H2S also to cardiac relaxation. H2S effects involve KATP channels, the Akt/NOS-cGMP/PKG pathway, and S-sulfhydration of cardiac proteins.

Effect of increased magnesium on recovery from ischemia in rat and rabbit hearts

1982 ◽  
Vol 242 (1) ◽  
pp. H89-H93
Author(s):  
M. M. Bersohn ◽  
K. I. Shine ◽  
W. D. Sterman
Keyword(s):  
Protective Effect ◽  
Rat Heart ◽  
Negative Inotropic Effect ◽  
Ischemic Myocardium ◽  
Inotropic Effect ◽  
Mechanical Function ◽  
Inotropic Response ◽  
Rat Hearts ◽  
Negative Inotropic Response

Perfusates containing high magnesium concentrations have been suggested to have a protective effect for ischemic myocardium, but the mechanism for such an effect is unclear. We investigated the recovery of isolated perfused rabbit and rat hearts from ischemia under varied conditions of increased Mg. Hearts were made ischemic in the presence of normal 1.2 mM Mg or elevated 15 mM Mg. Rabbit hearts, which show minimal alteration in contractility in the presence of 15 mM Mg, were not protected from ischemia by high Mg perfusate. Rat hearts, which have a large negative inotropic response to 15 mM Mg, exhibited significantly better recovery of mechanical function following ischemia in the presence of high Mg than following ischemia with normal Mg. This protective effect was abolished by increasing both Ca and Mg in the perfusate to prevent the decline in contractility that normally occurred with Mg. Reperfusion with 15 mM Mg after ischemia also had no protective effect if the rat heart had been made ischemic in the presence of normal Mg. We conclude that elevated Mg protects ischemic myocardium only under circumstances in which it has a negative inotropic effect before the onset of ischemia, i.e., in the rat heart perfused with normal Ca. These results suggest that the mechanism of protection by high Mg involves sparing of ATP. However, the different responses to Mg of the species studied in these experiments should be a caution against extrapolating such results from rat hearts to other species.

Responses of contractile function to ruthenium red in rat heart

1988 ◽  
Vol 255 (6) ◽  
pp. H1413-H1420 ◽  
Author(s):  
M. P. Gupta ◽  
I. R. Innes ◽  
N. S. Dhalla
Keyword(s):  
Rat Heart ◽  
Contractile Function ◽  
Negative Inotropic Effect ◽  
Ruthenium Red ◽  
Inotropic Effect ◽  
Inotropic Effects ◽  
Rat Hearts ◽  
Positive Inotropic Effects ◽  
High Concentrations

Isolated rat hearts exhibited a biphasic contractile response to varying concentrations of ruthenium red. A negative inotropic effect was observed with concentrations of 0.025–0.5 microM, whereas a reversal of these initial changes toward control or even exceeding the predrug values was obtained as ruthenium red concentration was increased to 2.5 or 5.0 microM. High concentrations (12.5–25.0 microM) of ruthenium red caused a sustained contracture. In contrast, isolated frog hearts exhibited only a sustained negative inotropic effect at 0.25–12.5 microM ruthenium red. In studies with rat heart, both negative and positive inotropic effects of 2.5 microM ruthenium red were blocked either by increasing the concentration of Ca2+ (from 1.25 to 5.0 mM) or by decreasing the concentration of Na+ (from 140 to 35 mM) in the perfusion medium. The contracture induced by 12.5 microM ruthenium red was markedly inhibited when Ca2+ in the medium was lowered. The positive inotropic effect and contracture due to ruthenium red were also blocked by 1 microM of verapamil and 1.5 mM of amiloride; however, these interventions did not prevent the initial negative inotropic effect of ruthenium red. These experiments suggest the role of extracellular Ca2+ in the dose- and time-dependent effects of ruthenium red on contractile function of the rat heart. Furthermore, the positive inotropic response to ruthenium red may be related to its actions on the Na+-dependent Ca2+ movements in the cardiac cell.

Mitochondrial KATP opening confers protection against lethal myocardial injury and ischaemia-induced arrhythmias in the rat heart via PI3K/Akt-dependent and -independent mechanismsThis article is one of a selection of papers published in a special issue on Advances in Cardiovascular Research.

2009 ◽  
Vol 87 (12) ◽  
pp. 1055-1062 ◽  
Author(s):  
Jana Matejíková ◽  
Táňa Ravingerová ◽  
Dezider Pancza ◽  
Slávka Čarnická ◽  
František Kolář
Keyword(s):  
Rat Heart ◽  
Myocardial Injury ◽  
Molecular Mechanisms ◽  
Antiarrhythmic Effect ◽  
Akt Inhibitor ◽  
Ischaemia Reperfusion Injury ◽  
Cardiovascular Research ◽  
Positive Role ◽  
Rat Hearts ◽  
Perfused Rat Hearts

Opening of mitochondrial KATP channels (mitoKATP) has been reported to underlie protection against ischaemia–reperfusion injury induced by ischaemic preconditioning (I-PC); however, the molecular mechanisms of its antiarrhythmic effect have not been fully elucidated. We explored the involvement of phosphatidylinositol 3-kinase (PI3K)/Akt in the PC-like effect of mitoKATP opener diazoxide with particular regard to its role in protection against ischaemia-induced arrhythmias. Langendorff-perfused rat hearts were subjected to 30 min LAD occlusion with or without a prior 15 min of perfusion with diazoxide (50 µmol/L) given either alone (D-PC) or in combination with the PI3K/Akt inhibitor wortmannin (100 nmol/L). In an additional protocol, ischaemia was followed by 2 h reperfusion for infarct size (IS) determination (tetrazolium staining). The total number of premature ventricular complexes over the whole period of ischaemia, episodes of ventricular tachycardia and its duration were significantly lower in the D-PC group than in the non-preconditioned controls (158 ± 20, 2 ± 0.6 and 4.6 ± 1.8 s vs. 551 ± 61, 11 ± 2 and 42 ± 8 s, respectively; p < 0.05), concomitant with a 62% reduction in the size of infarction. Wortmannin modified neither arrhythmogenesis nor IS in the non-preconditioned hearts. Bracketing of diazoxide with wortmannin did not reverse the antiarrhythmic protection, whereas the IS-limiting effect was blunted. The results indicate that in contrast with the positive role of PI3K/Akt in protection against lethal myocardial injury, its activity is not involved in suppression of ischaemia-induced arrhythmias conferred by mitoKATP opening in the rat heart.

scholarly journals Conversion of inactive (phosphorylated) pyruvate dehydrogenase complex into active complex by the phosphate reaction in heart mitochondria is inhibited by alloxan-diabetes or starvation in the rat

1978 ◽  
Vol 173 (2) ◽  
pp. 669-680 ◽  
Author(s):  
N J Hutson ◽  
A L Kerbey ◽  
P J Randle ◽  
P H Sugden
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Rat Heart ◽  
Pyruvate Dehydrogenase Complex ◽  
Diabetic Rats ◽  
Atp Depletion ◽  
Heart Mitochondria ◽  
Active Complex ◽  
Phosphate Complex ◽  
Rat Hearts ◽  
Dehydrogenase Complex

1. The conversion of inactive (phosphorylated) pyruvate dehydrogenase complex into active (dephosphorylated) complex by pyruvate dehydrogenase phosphate phosphatase is inhibited in heart mitochondria prepared from alloxan-diabetic or 48h-starved rats, in mitochondria prepared from acetate-perfused rat hearts and in mitochondria prepared from normal rat hearts incubated with respiratory substrates for 6 min (as compared with 1 min). 2. This conclusion is based on experiments with isolated intact mitochondria in which the pyruvate dehydrogenase kinase reaction was inhibited by pyruvate or ATP depletion (by using oligomycin and carbonyl cyanide m-chlorophenylhydrazone), and in experiments in which the rate of conversion of inactive complex into active complex by the phosphatase was measured in extracts of mitochondria. The inhibition of the phosphatase reaction was seen with constant concentrations of Ca2+ and Mg2+ (activators of the phosphatase). The phosphatase reaction in these mitochondrial extracts was not inhibited when an excess of exogenous pig heart pyruvate dehydrogenase phosphate was used as substrate. It is concluded that this inhibition is due to some factor(s) associated with the substrate (pyruvate dehydrogenase phosphate complex) and not to inhibition of the phosphatase as such. 3. This conclusion was verified by isolating pyruvate dehydrogenase phosphate complex, free of phosphatase, from hearts of control and diabetic rats an from heart mitochondria incubed for 1min (control) or 6min with respiratory substrates. The rates of re-activation of the inactive complexes were then measured with preparations of ox heart or rat heart phosphatase. The rates were lower (relative to controls) with inactive complex from hearts of diabetic rats or from heart mitochondria incubated for 6min with respiratory substrates. 4. The incorporation of 32Pi into inactive complex took 6min to complete in rat heart mitocondria. The extent of incorporation was consistent with three or four sites of phosphorylation in rat heart pyruvate dehydrogenase complex. 5. It is suggested that phosphorylation of sites additional to an inactivating site may inhibit the conversion of inactive complex into active complex by the phosphatase in heart mitochondria from alloxan-diabetic or 48h-starved rats or in mitochondria incubated for 6min with respiratory substrates.

scholarly journals Coronary vasodilation and positive inotropism by urocortin in the isolated rat heart

2001 ◽  
Vol 169 (1) ◽  
pp. 177-183 ◽  
Author(s):  
K Terui ◽  
A Higashiyama ◽  
N Horiba ◽  
KI Furukawa ◽  
S Motomura ◽  
...  
Keyword(s):  
Rat Heart ◽  
Isolated Rat Heart ◽  
Coronary Vasodilation ◽  
Duration Of Action ◽  
Inotropic Effects ◽  
Vasodilator Effect ◽  
Cardiac Effects ◽  
Positive Inotropic Effects ◽  
Isolated Rat

Corticotropin-releasing factor (CRF) has a coronary vasodilator effect and a positive inotropic effect on the isolated rat heart. Recently, expression of CRF receptor type 2 (CRF-R2) has been demonstrated in the heart. In addition, urocortin (Ucn), a new member of the CRF family, has been reported to have much greater affinity for CRF-R2 than CRF. It is suggested that the cardiac effects of Ucn may be more potent than those of CRF. We compared the effect of Ucn with that of CRF on isolated rat heart. The effects of Ucn were then analyzed to determine whether these effects were mediated by CRF receptors and/or any other mediators under the following conditions: perfusion buffer containing (1) alpha-helical CRF 9-41, (2) indomethacin, (3) N(G)-nitro-l -arginine methylester and (4) propranolol. Ucn exhibited a greater effect with a longer duration of action than CRF. Indomethacin significantly attenuated the vasodilator effects of Ucn (P<0.05). CRF receptor antagonist diminished both coronary vasodilation and the positive inotropic effects of Ucn (P<0.05). These results suggest that the cardiac effects of Ucn may be mediated by a CRF receptor, and prostaglandins may be involved in the vasodilator effect.

Metabolic fate of rat heart endothelial lipoprotein lipase

1988 ◽  
Vol 255 (3) ◽  
pp. E247-E254 ◽  
Author(s):  
T. Chajek-Shaul ◽  
G. Bengtsson-Olivecrona ◽  
J. Peterson ◽  
T. Olivecrona
Keyword(s):  
Lipoprotein Lipase ◽  
Lipase Activity ◽  
Rat Heart ◽  
Metabolic Fate ◽  
Low Concentrations ◽  
Rat Hearts ◽  
Catalytically Active ◽  
Isolated Rat

When isolated rat hearts were perfused with medium containing 125I-labeled bovine lipoprotein lipase (LPL), they bound both lipase activity and radioactivity. More than 80% of the bound lipase could be rapidly released by heparin. Low concentrations of bovine LPL displaced 50-60% of the endogeneous, endothelial-bound LPL. Higher concentrations caused additional binding. Both binding and exchange were rapid processes. The hearts continuously released endogenous LPL into the medium. An antiserum that inhibited bovine but not rat LPL was used to differentiate endogeneous and exogeneous LPL activity. When the pool of endothelial LPL was labeled with bovine 125I-labeled LPL and then chased with unlabeled bovine LPL, approximately 50% of the labeled lipase was rapidly displaced. During chase perfusion with medium only, catalytically active bovine LPL appeared in the perfusate. The rate of release was similar to that observed for endogeneous LPL activity and amounted to 10-13% of the heparin-releasable fraction in the first 5 min of perfusion. There was little or no degradation of bovine 125I-labeled LPL to fragments or acid-soluble products. These results indicate that endothelial LPL is accessible for exchange with exogeneous LPL and that detachment rather than degradation may be the pathway for catabolism of endothelial LPL.

Heterogeneity of the hypoxic state in rat heart is determined at capillary level

1993 ◽  
Vol 264 (2) ◽  
pp. H294-H301 ◽  
Author(s):  
C. Ince ◽  
J. F. Ashruf ◽  
J. A. Avontuur ◽  
P. A. Wieringa ◽  
J. A. Spaan ◽  
...  
Keyword(s):  
Rat Heart ◽  
High Flow ◽  
Rat Hearts ◽  
Nadh Fluorescence ◽  
Perfused Rat Hearts ◽  
Hypoxic State ◽  
Microsphere Embolization

Heterogeneity in the hypoxic state of Tyrode-perfused rat hearts was studied using NADH and Pd-porphine videofluorometry. Ischemic as well as high-flow anoxia resulted in a homogeneous rise of tissue NADH fluorescence, whereas normoxic recovery from both types of anoxia caused transiently persisting patchy fluorescent areas. Patterns were always the same for a given heart. PO2 distribution in the vasculature measured by Pd-porphine phosphorescence showed patterns similar to the NADH fluorescence patterns. Microsphere embolization of the capillaries, but not of arterioles, elicited identical NADH fluorescence patterns as seen during recovery from anoxia without microspheres. High heartbeat rates also caused patchy fluorescent areas but not in the presence of adenosine. Patterns corresponded to those seen during normoxic recovery from anoxia under low beat rates. It is concluded that there are circulatory units in the rat heart at the capillary level that result in the temporary persistence of anoxic areas during recovery from anoxia. These vulnerable areas are the first to be compromised during high heartbeat rates.

Reduced high-energy phosphate levels in rat hearts. I. Effects of alloxan diabetes

1976 ◽  
Vol 230 (6) ◽  
pp. 1744-1750 ◽  
Author(s):  
TB Allison ◽  
SP Bruttig ◽  
Crass MF ◽  
RS Eliot ◽  
JC Shipp
Keyword(s):  
Oxidative Metabolism ◽  
Oxygen Delivery ◽  
Rat Heart ◽  
High Energy ◽  
Diabetic Rat ◽  
High Energy Phosphate ◽  
Atp Production ◽  
Rat Hearts

Significant alterations in heart carbohydrate and lipid metabolism are present 48 h after intravenous injection of alloxan (60 mg/kg) in rats. It has been suggested that uncoupling of oxidative phosphorylation occurs in the alloxanized rat heart in vivo, whereas normal oxidative metabolism has been demonstrated in alloxan-diabetic rat hearts perfused in vitro under conditions of adequate oxygen delivery. We examined the hypothesis that high-energy phosphate metabolism might be adversely affected in the alloxan-diabetic rat heart in vivo. Phosphocreatine and ATP were reduced by 58 and 45%, respectively (P is less than 0.001). Also, oxygen-dissociation curves were shifted to the left by 4 mmHg, and the rate of oxygen release from blood was reduced by 21% (P is less than 0.01). Insulin administration normalized heart high-energy phosphate compounds. ATP production was accelerated in diabetic hearts perfused in vitro with a well-oxygenated buffer. These studies support the hypothesis that oxidative ATP production in the alloxan-diabetic rat heart is reduced and suggest that decreased oxygen delivery may have a regulatory role in the oxidative metabolism of the diabetic rat heart.

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