Journal of molecular and cellular cardiology
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J. Mol. Cell. Cardiol. · Mar 1998
Adenine/ribose supply increases adenosine production and protects ATP pool in adenosine kinase-inhibited cardiac cells.
The objective of the present study was to establish the optimal combination of inhibitors of adenosine metabolism and nucleotide precursors resulting in long-term increase in endogenous adenosine concentration without adverse metabolic consequences in non-ischemic cardiomyocytes and endothelial cells. Cardiomyocytes and endothelial cells were isolated after collagenase digestion of the rat heart. Freshly isolated cardiac myocytes or cultured endothelial cells were incubated for up to 8 h with no inhibitors or substrates or with various combinations of adenosine deaminase inhibitor: 5 micron M erythro-9(2-hydroxy-3-nonyl)adenine (EHNA), adenosine kinase inhibitors: 10 micro M 5'-iodotubercidin (ITu) or 10 micro M 5'-aminoadenosine (AA) and nucleotide precursors: 100 micro M adenine, 2.5 mm ribose and 5 mm inorganic phosphate. ⋯ No changes in adenylate energy charge were observed in cardiomyocytes or endothelium under any conditions studied. Inhibition of adenosine kinase and adenosine deaminase caused a decrease in ATP together with increased adenosine content both in endothelial cells and cardiomyocytes. However, the addition of adenine (endothelial cells) or adenine with ribose (cardiomyocytes) together with inhibitors of adenosine metabolism protected cells from ATP depletion and further increased adenosine concentration.
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J. Mol. Cell. Cardiol. · Feb 1998
Protein tyrosine kinase is downstream of protein kinase C for ischemic preconditioning's anti-infarct effect in the rabbit heart.
The present study tested the hypothesis that one or more tyrosine kinase(s) are downstream of protein kinase C (PKC) in the signal transduction pathway responsible for the cardioprotective effect of ischemic preconditioning (PC). Isolated rabbit hearts were subjected to 30 min of regional ischemia followed by 2 h of reperfusion. Infarct size was measured by triphenyltetrazolium staining and expressed as a percentage of the area at risk. ⋯ Conversely, anisomycin (50 ng/ml), an activator of MAP kinase kinases (dual tyrosine and threonine kinases), was very protective (7.5+/-1.6%; P<0.05) and this protection was still present when PKC was inhibited by 5 microM chelerythrine (12.1+/-1.6%; P<0.05). In conclusion, activation of a tyrosine kinase during the long ischemia appears to be required for cardioprotection in the rabbit heart. Furthermore, the ability of tyrosine kinase inhibitors to block PMA-induced protection in conjunction with the failure of PKC inhibition to prevent anisomycin-induced protection suggests that the tyrosine kinase is downstream of PKC and that the tyrosine kinase may be a MAP kinase kinase.
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J. Mol. Cell. Cardiol. · Aug 1997
Comparative StudyIschemic preconditioning and morphine-induced cardioprotection involve the delta (delta)-opioid receptor in the intact rat heart.
Several investigators have demonstrated that the opioid pathway is involved in tissue preservation during hypoxia or ischemia and that this protection is mediated via the delta (delta)-opioid receptor. Subsequently, we have shown that opioid receptors are involved in ischemic preconditioning (PC) in the rat heart and that morphine produces a cardioprotective effect; however, the class of opioid receptors involved in mediating these effects is still unknown. Therefore, the purpose of the present study was to test the hypothesis that ischemia- and morphine-induced cardioprotection are mediated via stimulation of the delta-opioid receptor in the rat heart. ⋯ Ischemic PC and morphine infusions resulted in similar reductions in IS/AAR from 51+/-4 to 11+/-3 and 15+/-4% (*P<0.05), respectively. NTI completely abolished the cardioprotective effect induced by ischemia and morphine. The results of the present study suggests a role of delta;-opioid receptors in ischemic PC or morphine-induced myocardial protection in the rat.
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J. Mol. Cell. Cardiol. · Jun 1997
Effects of cromakalim and glibenclamide on myocardial high energy phosphates and intracellular pH during ischemia-reperfusion: 31P NMR studies.
ATP sensitive potassium channel (KATP) openers (e.g. cromakalim) are thought to be cardioprotective during ischemia-reperfusion, while KATP blockers (e.g. glibenclamide) may potentiate ischemia-reperfusion damage. We studied cardiac energetics and intracellular pH, by 31P magnetic resonance spectroscopy, during ischemia-reperfusion of buffer perfused, isolated rat hearts in the presence of cromakalim (10 microM) or glibenclamide (1, 10 and 50 microM). Hearts were subjected to 25 min total global ischemia at 36.5 degrees C and reperfused for 45 min. ⋯ During ischemia, intracellular ATP was depleted more rapidly in the presence of 50 microM glibenclamide and intracellular acidosis was significantly attenuated (final pH 6.3 v 5.8 for control). 50 microM glibenclamide also decreased tissue lactate content at the end of ischemia (75 +/- 3 mumol/g dry weight v 125 +/- 18 for control, P < 0.05) and this attenuation of lactate accumulation and consequent decreased intracellular acidosis may be responsible for the cardioprotection observed under these conditions. These latter effects are unlikely to be related to glibenclamide's KATP blocking activity. This study demonstrates that blocking of myocardial KATP does not potentiate ischemia-reperfusion injury and, in addition, illustrates the important role played by intracellular acidosis in myocardial ischemia-reperfusion injury.
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J. Mol. Cell. Cardiol. · May 1997
Beta-adrenergic receptor signalling in stunned myocardium of conscious pigs.
The primary goal of this study was to compare the effects of isoproterenol which stimulates beta-adrenergic receptors and forskolin, and NKH 477, a water soluble derivative of forskolin, which stimulate adenylyl cyclase in stunned myocardium of conscious pigs, previously instrumented for measurements of left ventricular pressure and dP/dt, arterial pressure, and wall thickening. Ten min of coronary artery occlusion induced transmural reductions in blood flow (radioactive microspheres) in subepicardium (-98 +/- 2%) and subendocardium (-99 +/- 1%). Wall thickening (piezoelectric crystals) fell from 2.50 +/- 0.26 mm to -0.26 +/- 0.26 mm and remained depressed at 1.37 +/- 0.19 mm after 20-30 min coronary artery reperfusion, reflecting myocardial stunning. ⋯ Basal and forskolin-stimulated adenylyl cyclase activities were decreased slightly, but significantly, in the stunned subendocardium but not in the subepicardium, while isoproterenol stimulation of adenylyl cyclase activity showed no differences. In summary, paradoxical responses to beta-adrenergic receptor stimulation were observed in stunned myocardium, with pharmacological stimulation with isoproterenol evoking enhanced responses, and neural stimulation with inferior vena caval occlusion eliciting depressed responses. The diminished responses to forskolin in vivo, in stunned myocardium were out of proportion to the biochemical measurements, and may be attributed to neurally mediated cardiac effects of forskolin, since the responses to direct stimulation of adenylyl cyclase by NKH 477 were preserved.