bluuebunny/crossref_metadata_2025 huggingface dataset:
Perfusion-MVO2 mismatch during inotropic stress in CAD patients with normal contractile function
Authors: Janier M. F. , Andre-Fouet X. , Landais P. , Gregoire M. C. , Lavenne F. , Amaya J. , Mercier C. , Machecourt J. , Cinotti L.
Published: December 2017

With the use of[11C]acetate, positron emission tomography (PET) permits exploration of myocardial blood flow (MBF) and oxidative metabolism (MVo2) coupling. PET imaging was performed at rest and under dobutamine infusion in 8 normal subjects and 10 coronary artery disease (CAD) patients with significant single-vessel left anterior descending (LAD) stenosis (> 70%) and normal regional left contractile function at rest. Resting MBF and MVo2 were similar in remote and LAD regions of normal subjects and patients. During dobutamine infusion, MBF and myocardial flow reserve were lower in LAD regions of patients compared with remote regions (MBF: 1.49 +/- 0.42 and 2.06 +/- 0.57 ml.g-1.min-1, P < 0.01; reserve: 1.73 +/- 0.59 and 2.14 +/- 0.47, P < 0.01, respectively), whereas MVo2 expressed as kmono (an index of MVo2) and metabolic reserve were similar (kmono: 0.106 +/- 0.021 vs. 0.107 +/- 0.017 min-1; reserve: 1.88 +/- 0.32 vs. 1.98 +/- 0.37, respectively). This is the first human study showing that, in normal contractile regions at rest but perfused by stenosed artery, a disparate rise in MVo2 relative to the rise in myocardial perfusion occurs during increased cardiac work induced by dobutamine. This flow-metabolism uncoupling probably reflects an increase in O2 extraction.
Heart rate variability during artificial ventilation and apnea in brain-damaged rabbits
Authors: Kawamoto M. , Kaneko K. , Yuge O.
Published: December 2017

The effect of artificial ventilation, apnea, and norepinephrine administration on heart rate variability was determined in brain-damaged rabbits. Electrocardiographic R-R intervals and circulatory variables were measured for 5 min at three different ventilatory frequencies, including apnea under isoflurane general anesthesia. The same measurements were repeated after brain damage was inflicted by an inflated intracranial balloon. In control rabbits (n = 8) and in those receiving norepinephrine (n = 8), power spectral analysis of R-R intervals was repeated, and spectral components of low (LF: 0.04-0.09 Hz), mid (MF: 0.09-0.15 Hz), and high (HF: 0.15-0.40 Hz) frequency band areas were assessed. LF + MF (P < 0.05) increased during apnea, whereas HF did not change under general anesthesia. However, after brain damage in both groups LF + MF did not change, whereas HF was depressed (P < 0.05). There was no intergroup difference in decreases of HF/(LF + MF) (P < 0.05) during apnea under either condition. Norepinephrine increased heart rate and arterial pressure (P < 0.05) but did not produce any intergroup difference in the spectral components. We suggest that sympathovagal balance is apt to be sympathotonic during apnea under general anesthesia, whereas it is vagolytic with brain damage.
Regulation of sodium current development in cultured atrial tumor myocytes (AT-1 cells)
Authors: Yang T. , Roden D. M.
Published: December 2017

AT-1 cells, derived from atrial tumors in transgenic mice, have many features similar to cardiac myocytes. However, their sodium current (INa) has not been evaluated on detail. In this study, two INa phenotypes were identified in AT-1 cells: one at 3 days in culture and the other at 14 days. INa was smaller at 3 days than at 14 days (12 +/- 2 vs. 37 +/- 5 pA/pF) and activated more slowly (time to peak INa at -30 mV: 9.8 +/- 0.4 vs. 1.4 +/- 0.1 ms). Inactivation at 14 days was faster and shifted 16 mV negative compared with that at 3 days. Acute protein kinase A or C stimulation in 3-day cells did not alter INa gating. However, the 14-day phenotype was observed in 3-day cells when the adenosine 3',5'-cyclic monophosphate analogue 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate, the phorbol ester phorbol 12-myristate 13-acetate, or okadaic acid was added to the culture medium from days 0 to 3. Conversely, adenosine 3',5'-cyclic monophosphothioate triethylamine, the protein kinase A inhibitor, prevented the normal development of the 14-day phenotype if the exposure was early and reverted the phenotype to that at 3 days if the exposure was later. Thus, in AT-1 cells, as in other mammalian cardiac myocytes, INa undergoes a maturation process that is dependent on intracellular phosphorylation processes. The data raise the possibility that an important consequence of altered intracellular signaling in disease is lability in INa amplitude or gating.
Vitamin E ameliorates adverse effects of endothelial injury in brain arterioles
Authors: Rosenblum W. I. , Nelson G. H. , Bei R. A. , Brandt R. B. , Chan W.
Published: December 2017

Endothelium-dependent dilation, produced by applying acetylcholine (ACh) to pial arterioles, was unaffected after 6 mo of a diet with zero vitamin E or 8 mo of a vitamin E-enriched diet. The enriched diet did not affect constriction produced by topically applied NG-monomethyl-L-arginine, an inhibitor of the synthesis of endothelium-derived relaxing factor (EDRF). EDRF mediates the response to ACh and is a basally released dilator and antiplatelet paracrine substance. Endothelial injury produced by a helium-neon laser and Evans blue technique eliminates the response to ACh, but in vitamin E-enriched mice the response to ACh was unaffected by the injury. More prolonged exposure of the laser induces platelet adhesion/aggregation at the injured site. A significantly longer exposure to the laser was required to initiate adhesion/aggregation in vitamin E-enriched mice. Because effects of endothelial damage in this model are mediated at least in part by singlet oxygen produced by injured tissue (W.I. Rosenblum and G.H. Nelson, Am. J. Physiol. 270 (Heart Circ. Physiol. 39): H1258-H1263, 1996.), we conclude that the antioxidant, radical-scavenging actions of vitamin E explain the protective action of the vitamin E-enriched diet. However, raising vitamin E levels did not protect against putative adverse effects of normally occurring oxidants.
Cellular response to reperfused oxygen in the postischemic myocardium
Authors: Chung Y. , Jue T.
Published: December 2017

Perfused rat heart experiments focused on determining the critical O2 level in postischemic myocardium. After a 20-min global ischemia, reperfusion began with O2-saturated saline buffer reflowing at different rates (0.5-12 ml/min). The 1H nuclear magnetic resonance (NMR) signal of the Val E11 myoglobin (Mb) gave an index of the intracellular oxygenation, whereas the 31P-NMR spectra reflected the high-energy phosphate and pH status. At the same time, physiological monitors recorded both contractile function and O2 consumption. Biochemical analysis determined the lactate concentration. Within 6-12 min of reperfusion, the O2 reached a new steady state, which depended directly on the flow rate. Below 12 ml/min reflow, the postischemic O2 level was consistently lower than the corresponding control values. Phosphocreatine, P(i), pH, myocardial O2 consumption, and lactate formation rate exhibited a similar linear relationship with MbO2 saturation in both the control and postischemic myocardium. It appears that neither the cellular energy production nor the steep intracellular O2 gradient has changed substantially in the postischemic myocardium.
Exogenous tetrahydrobiopterin causes endothelium-dependent contractions in isolated canine basilar artery
Authors: Kinoshita H. , Katusic Z. S.
Published: December 2017

Tetrahydrobiopterin is an essential cofactor in the biosynthesis of nitric oxide, but in the presence of O2, autooxidation of tetrahydrobiopterin leads to the production of superoxide anions and the subsequent chemical inactivation of nitric oxide. As a result, the present experiments were designed to determine the effect of exogenous tetrahydrobiopterin on isolated canine basilar arteries. Rings with and without endothelium were suspended for isometric force recording in modified Krebs-Ringer bicarbonate solution bubbled with 94% O2-6% CO2 (37 degrees C; pH 7.4). A radioimmunoassay technique was used to measure guanosine 3',5' cyclic monophosphate production (cGMP). Tetrahydrobiopterin (10(-7) to 10(-4) M), but not dihydrobiopterin or biopterin, caused endothelium-dependent contractions. Superoxide dismutase (150 U/ml) abolished tetrahydrobiopterin-induced contractions, but a H2O2 scavenger, catalase (1,200 U/ml), and hydroxyl radical scavengers deferoxamine (10(-4) M) and dimethylsulfoxide (10(-4) to 10(-3) M) did not significantly affect the contractions. A cyclooxygenase inhibitor, indomethacin (10(-5) M), significantly reduced the contractile effect of tetrahydrobiopterin. With the prostaglandin H2/ thromboxane A2 receptor antagonist, SQ-29548 (10(-6) M) present, contractions reversed to relaxations. In rings with endothelium, tetrahydrobiopterin (10(-4) M) significantly decreased the levels of cGMP. These studies suggest that autooxidation of exogenous tetrahydrobiopterin induces endothelium-dependent contractions by 1) chemical inactivation of nitric oxide by superoxide anions and 2) activation of arachidonic acid metabolism via the cyclooxygenase pathway with subsequent release of endoperoxide and/or thromboxane A2 from endothelial cells.
Blockade of lysophosphatidylcholine-modified cardiac Na channels by a lidocaine derivative QX-222
Authors: Undrovinas A. I. , Makielski J. C.
Published: December 2017

Single Na channels from rat and rabbit ventricular cells were studied with use of the excised inside-out patch-clamp technique. To investigate local anesthetic interactions with Na channels modified by the ischemic metabolite lysophosphatidylcholine (LPC), the quaternary ammonium lidocaine derivative QX-222 [2-(trimethylamino)-N-(2,6-dimethylphenyl)acetamide] was applied to the cytoplasmic side of patches from untreated cells and from those treated with LPC for approximately 1 h. Single-channel amplitudes and kinetics for unmodified channels were similar to those reported previously for cardiac cells with a single-component, mean-channel open time. LPC-modified channels showed prolonged open channel bursting with a two-component, mean open time, suggesting two open states. Conductance sublevels to the 60-70% level of the main conductance were found in both unmodified and LPC-modified channels and also with and without QX-222 present. QX-222 reversibly shortened the open time of the unmodified channel and for both open times of the LPC-modified channel without decreasing single-channel amplitude. Calculated association rates for QX-222 with the channel were found to be greater for the open states of the modified channel than those for the unmodified channel. Thus the lidocaine analogue QX-222 interacts with and blocks the open state of both unmodified and LPC-modified, cardiac Na channels. The blocking effect on LPC-modified channels would be predicted to be greater both because of the longer dwell time in the high-affinity open states for modified channels and also because of an intrinsically greater association rate in the modified channels.
Expression and localization of renin and angiotensinogen in rat heart after myocardial infarction
Authors: Passier R. C. , Smits J. F. , Verluyten M. J. , Daemen M. J.
Published: December 2017

Wistar-Kyoto rats underwent myocardial infarction (MI) or sham surgery. At different time points after surgery (1-90 days), hearts were removed and divided into infarcted left ventricle (LV), noninfarcted septum, and right ventricle. The tissues were used for total RNA isolation or Formalin fixation for in situ hybridization (ISH). Renin and angiotensinogen mRNA contents were quantified by the competitive reverse transcriptase polymerase chain reaction. We found a 4-, 14-, and 8-fold increase (P < 0.05, n = 6) in renin mRNA in the infarcted LV at 2, 4, and 7 days after MI, respectively. No differences were observed between angiotensinogen mRNA levels in sham and infarcted hearts. ISH at 4 days after surgery revealed a dense renin mRNA labeling around the infarcted area, whereas ISH of angiotensinogen displayed an overall low density in the myocardium with somewhat higher levels in the epicardium of sham and MI animals. Atrial natriuretic factor mRNA, a marker for cardiac hypertrophy, was approximately twofold higher in all compartments of the hearts after MI. The low amounts of renin and angiotensinogen mRNA in the noninfarcted hypertrophied myocardium indicate that the intracardiac synthesis of these components does not play a dominant role in the development of cardiac hypertrophy in the rat heart after MI. In addition, the increased renin mRNA expression in the border zone of the infarcted LV suggests a role for intracardiac angiotensin II in infarct healing.
Free radicals enhance Na+/Ca2+ exchange in ventricular myocytes
Authors: Goldhaber J. I.
Published: December 2017

Oxygen-derived free radicals (OFR) have been implicated in the pathogenesis of intracellular Ca2+ overload and the arrhythmias that characterize cardiac reperfusion. These arrhythmias may in large part be due to activation of the pathological transient inward current (ITI). However, the identity of the ITI generated by OFR is uncertain. We previously found that H2O2, an OFR-generating compound, markedly stimulated the ITI elicited by brief caffeine pulses in patch-clamped guinea pig ventricular myocytes. In the present study, using patch-clamped rabbit ventricular myocytes loaded with the Ca(2+)-sensitive indicator fura 2, we have further characterized this ITI and have identified its major component to be Na+/Ca2+ exchange based on its dependence on extracellular Na+ and sarcoplasmic reticulum Ca2+ release, its sensitivity to Ni2+, and the effects of its inhibition on relaxation. The effect on ITI was not unique to H2O2, because another free radical-generating system, xanthine + xanthine oxidase, produced a similar response. We hypothesize that enhancement of Na+/Ca2+ exchange by OFR during reperfusion, when intracellular Na+ is elevated, may promote intracellular Ca2+ overload and triggered arrhythmias.
Effect of preconditioning on ryanodine-sensitive Ca2+ release from sarcoplasmic reticulum of rat heart
Authors: Tani M. , Asakura Y. , Hasegawa H. , Shinmura K. , Ebihara Y. , Nakamura Y.
Published: December 2017

The effect of varying the number of preconditioning (PC) episodes on the recovery of cardiac function and on the function of the sarcoplasmic reticulum (SR) was investigated to determine the correlation between the effect of PC and SR function. Isolated rat hearts were subjected to zero to three 5-min episodes of global ischemia with intermittent perfusion (PC0-PC3) followed by 25 min of ischemia (I) and 30 min of reperfusion. The left ventricular (LV) pressure and SR 45Ca2+ uptake in the absence or presence of ryanodine were then measured. The increase in LV end-diastolic pressure and the incidence and duration of ventricular tachyarrhythmias during reperfusion decreased. The recovery of LV developed pressure, LV dP/dtmax and dP/dtmin, increased as the number of episodes of PC increased. The rates of SR 45Ca2+ uptake after PC and after reperfusion were lower in PC3 than in PC0. Conversely, the rate of 45Ca2+ uptake after I did not differ between PC0 and PC3. The ryanodine-sensitive Ca2+ release increased after I, and additional increases were observed during reperfusion in PC0, whereas the release after I and reperfusion decreased progressively in PC3. These observations show that the beneficial effects of PC are associated with a decrease in ryanodine-sensitive SR Ca2+ release.
Direct in vivo effects of nitric oxide on the coronary circulation
Authors: Chambers J. W. , Voss G. S. , Snider J. R. , Meyer S. M. , Cartland J. L. , Wilson R. F.
Published: December 2017

To determine the direct in vivo effects of nitric oxide (NO) on the coronary circulation, we infused NO-saturated saline (1.0 +/- 0.1 mmol/l) into the coronary arteries of anesthetized dogs and measured changes in coronary blood flow velocity (CBFV) with a Doppler catheter, changes in coronary artery size with quantitative angiography, and transmural myocardial perfusion with radioactive microspheres. Boluses of NO (1-8 micromol) caused a stepwise increase in CBFV (3.1 +/- 0.3 x basal CBFV at 8 micromol) similar to that caused by adenosine (2.6 +/- 0.3 x basal CBFV, maximal dose). Continuous subselective infusions (0.1, 1.0, and 4.0 micromol/min) caused dose-dependent increases in CBFV (2.2 +/- 0.3 x basal CBFV at 4.0 micromol/min) and in epicardial artery diameter (+ 15 +/- 6% diam). Left main infusions (8 micromol/min) caused a stepwise increase in CBFV and in the endocardial-to-epicardial flow ratio without affecting systemic hemodynamics. Brief infusion of NO (2 min) did not significantly reduce acetylcholine-mediated endothelial NO release. Therefore, despite rapid metabolism, direct intra-arterial infusion of NO can be given at a rate sufficient to overwhelm metabolic elimination, providing direct evidence that NO is a potent in vivo coronary vasodilator. Moreover, the enhanced subendocardial vasodilator response to direct NO infusion suggests increased regional sensitivity to NO.
Ischemic preconditioning in human and rat ventricle
Authors: Cleveland J. C. , Wollmering M. M. , Meldrum D. R. , Rowland R. T. , Rehring T. F. , Sheridan B. C. , Harken A. H. , Banerjee A.
Published: December 2017

The signal transduction of ischemic preconditioning involves activation of endogenous receptor-based systems, including alpha 1-adrenoceptors and adenosine receptors. Whereas preconditioning protects against ischemia-reperfusion injury, it is unknown whether this protective strategy might be useful clinically. Furthermore, human atrium has been successfully preconditioned, but it is unknown whether human ventricle can be functionally protected against hypoxia-reoxygenation. To study these questions, isolated rat ventricle and human ventricular trabeculae were suspended in an organ bath and subjected to 30 min of hypoxia and 60 min of reoxygenation. In the rat ventricle, preconditioning was induced by 5 min of rapid pacing at 3 Hz in hypoxic buffer without glucose (simulated ischemia), alpha 1-adrenoceptor stimulation (phenylephrine), or adenosine receptor stimulation (adenosine). In the human trabeculae the effects of preceding simulated ischemia and alpha 1-adrenoceptor and adenosine receptor stimulation were examined against hypoxia-reoxygenation. In the rat, pretreatment with simulated ischemia and alpha 1-adrenoceptor and adenosine receptor stimulation improved recovery of developed tension (56 +/- 3, 56 +/- 4, and 58 +/- 2%, respectively) compared with control trabeculae (25 +/- 2%) after hypoxia-reoxygenation (P < 0.05). In human trabeculae, simulated ischemic preconditioning and alpha 1-adrenoceptor and adenosine receptor stimulation augmented recovery of developed tension (65 +/- 5, 59 +/- 6, and 60 +/- 3%, respectively) compared with control (29 +/- 2%) after hypoxia-reoxygenation (P < 0.05). We conclude that functional cardioadaptation (preconditioning) against hypoxia-reoxygenation injury in rat and human myocardium exists and that alpha 1-adrenergic and adenosine receptor signaling participate in conferring this protection.
Mechanisms of protection afforded by preconditioning to endothelial function against ischemic injury
Authors: Bouchard J. F. , Lamontagne D.
Published: December 2017

The aim of this study was to assess whether the cardioprotective effect of ischemic preconditioning (IPC) on endothelial function in resistance coronary arteries of the rat involves adenosine and/or activation of ATP-sensitive K+ channels (KATP channels). Isolated rat hearts perfused under constant-flow conditions were exposed to 30 min of partial ischemia (flow rate 1 ml/min) followed by 20 min of reperfusion. Preconditioning was performed with 5 min of ischemia and 10 min of reperfusion before the 30-min ischemia. After the 20-min reperfusion period, coronary arteries were precontracted with U-46619 (0.1 microM), and the coronary response to the endothelium-dependent vasodilator serotonin (5-HT; 10 microM) was compared with that of the endothelium-independent vasodilator sodium nitroprusside (SNP; 3 microM). KATP channels or adenosine receptors were blocked with perfusion of either glibenclamide (0.3 microM) or 8-phenyltheophylline (8-PT; 5 microM), respectively, starting 15 min before IPC or a corresponding sham period. In untreated hearts, ischemia selectively diminished 5-HT-induced vasodilation, compared with sham hearts (without ischemia). The vasodilation by SNP was unaffected after ischemia and reperfusion. Preconditioning in untreated hearts preserved the vasodilation produced by 5-HT. Treatment of hearts with either glibenclamide or 8-PT halved the vasodilation produced by both 5-HT and SNP in sham hearts. Glibenclamide reduced by one-half, whereas 8-PT completely blocked, the protective effect of IPC on endothelium-dependent vasodilation. These results suggest that IPC affords protection to endothelial function in resistance coronary arteries of the rat partially by activation of KATP channels. Adenosine plays a major role in that protection.
Reloading of Ca(2+)-depleted sarcoplasmic reticulum during rest in guinea pig ventricular myocytes
Authors: Terracciano C. M. , MacLeod K. T.
Published: December 2017

The effects of rest on a Ca(2+)-depleted sarcoplasmic reticulum (SR) in guinea pig ventricular myocytes were investigated. Cell shortening was measured using a video edge-detection system, and cytoplasmic Ca2+ was monitored using the fluorescent indicator indo-1. Rapid cooling and rewarming in the presence of 10 mM caffeine were used to deplete the SR of Ca2+. The resting cell was then superfused for variable time intervals with a normal Tyrode solution containing 2 mM Ca2+. Another rapid cooling in caffeine was performed to assess the SR Ca2+ load at the end of rest. Rapid cooling after 1- and 2-min rest elicited an increase of indo-1 fluorescence of 51.9 +/- 7.7 (n = 17) and 72.7 +/- 6.7% of control (n = 9), respectively. This increase was not detectable when Ca2+ was absent from the superfusing solution. In contrast, the increase was larger when external Ca2+ was elevated to 4 mM. Nickel (5 mM) and nifedipine (20 microM) added to the superfusing solution during the rest interval did not alter the increase in indo-1 fluorescence. We conclude that Ca2+ is reaccumulated by a depleted SR during rest. Although this Ca2+ seems to originate from the extracellular space, its route from there to the SR is unclear.
Roles of calcium and kinases in regulation of thrombin-stimulated preproendothelin-1 transcription
Authors: Marsen T. A. , Simonson M. S. , Dunn M. J.
Published: December 2017

The release of the vasoactive peptide endothelin-1 (ET-1) is Ca2+ dependent after thrombin stimulation; however, little is known about the pathways involved. We studied the importance of Ca(2+)-dependent signal transduction pathways on preproET-1 mRNA induction in human endothelial cells. Thrombin-mediated preproET-1 mRNA induction was inhibited after clamping of cytosolic free CA2+ concentration ([Ca2+]i) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid. Chelation of extracellular Ca2+ with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid also had a significant inhibitory effect on the induction of preproET-1 mRNA. The Ca2+ ionophore A23187 induced constitutive as well as thrombin-stimulated preproET-1 mRNA expression. Mobilization of Ca2+ stores into the cytosol by inhibition of endoplasmic reticulum Ca(2+)-adenosinetriphosphatase with thapsigargin was effective also in inducing preproET-1 mRNA. Calmodulin antagonists W-7 and calmidazolium, as well as Ca2+/calmodulin-dependent kinase II inhibitor KN-62, significantly reduced thrombin-induced preproET-1 mRNA. Inhibition by cyclosporin A of the Ca(2+)-calmodulin-dependent phosphatase calcineurin potentiated constitutive preproET-1 mRNA. These data suggest that, in human endothelial cells, thrombin-mediated preproET-1 gene induction is regulated by a stimulatory Ca2+/calmodulin kinase II-dependent pathway.
Protease inhibition attenuates microvascular dysfunction in postischemic skeletal muscle
Authors: Carden D. L. , Korthuis R. J.
Published: December 2017

Neutrophils accumulate in skeletal muscle subjected to ischemia-reperfusion and appear to contribute to reperfusion-induced microvascular dysfunction. The overall objective of this study was to assess the role of the neutrophilic hydrolytic enzyme elastase in ischemia-reperfusion-induced granulocyte accumulation and microvascular dysfunction in skeletal muscle. We examined the effect of three structurally unrelated elastase inhibitors [eglin C, MeOsuc-Ala-Ala-Val-CH2Cl (MAAPV), or L-658758], administered at the onset of reperfusion, on neutrophil content and the increase in microvascular permeability induced by 4 h of ischemia and 0.5 h of reperfusion in the isolated canine gracilis muscle. Changes in vascular permeability (1 - sigma) were assessed by determining the solvent drag reflection coefficient for total plasma proteins (sigma) in the following groups: 1) 4.5 h of continuous perfusion (nonischemic), 2) ischemia-reperfusion alone, 3) ischemia-reperfusion + eglin C, 4) ischemia-reperfusion + MAAPV, and 5) ischemia-reperfusion + L-658758. Muscle neutrophil content was monitored by assessing tissue myeloperoxidase (MPO) activity in biopsies obtained at the end of the experiments. In nonischemic muscles, 1 - sigma and MPO activity averaged 0.13 +/- 0.03 and 0.7 +/- 0.2 units/g wet wt, respectively. Ischemia-reperfusion was associated with marked increases in microvascular permeability (1 - sigma = 0.39 +/- 0.02) and muscle MPO activity (8.9 +/- 1.2 units/g wet wt) that were attenuated by eglin C, MAAPV, and L-658758 (1 - sigma = 0.21 +/- 0.01, 0.22 +/- 0.02, and 0.21 +/- 0.03, respectively; MPO activity = 2.7 +/- 0.4, 2.1 +/- 0.8, and 2.8 +/- 1.8 units/g wet wt, respectively). These results suggest that granulocyte accumulation in postischemic skeletal muscle is dependent on the release of elastase from activated phagocytic cells. Moreover, neutrophilic elastase appears to play a major role in reperfusion-induced increases in microvascular permeability in skeletal muscle.
Endothelin receptors are modulated in association with endogenous fluctuations in estrogen
Authors: Barber D. A. , Sieck G. C. , Fitzpatrick L. A. , Miller V. M.
Published: December 2017

Experiments were designed to determine whether endogenous physiological fluctuations in sex steroid hormones affect expression or functional responses of endothelin receptors. Coronary arteries from sexually mature male, female, and ovariectomized pigs were prepared either for receptor binding or measurement of isometric force in organ chambers. Competitive binding of 125I-labeled endothelin-1 was significant for a one-site model with unlabeled endothelin-1 and a two-site model with unlabeled endothelin-3 and sarafotoxin S6c in all pigs. The total number of binding sites for all endothelin ligands was not different between male and female pigs. Binding affinities for the high-affinity binding site for both endothelin-3 and sarafotoxin S6c were significantly greater (lower inhibition constant) in membranes prepared from female pigs with high endogenous estrogen. In organ chamber experiments, contractions to endothelin-1 but not endothelin-3 or sarafotoxin S6c were significantly greater in coronary arterial rings from female compared with male pigs and were not affected significantly by removal of the endothelium or by treatment of the rings with either indomethacin (10(-5) mol/l) or the combination of indomethacin and NG-monomethyl-L-arginine (10(-4) mol/l). These results suggest endogenous fluctuations in estrogen are associated with an increase in affinity of a high-affinity endothelin receptor in coronary arterial smooth muscle of female pigs. In addition, independent of endogenous estrogen status, coronary arteries from female pigs generate significantly greater contractions to endothelin-1 compared with male pigs. This phenomenon occurs at the level of smooth muscle and is not dependent on the endothelium or synthesis of nitric oxide or prostaglandins.
Effect of nutritional state on substrate metabolism and contractile function in postischemic rat myocardium
Authors: Montessuit C. , Papageorgiou I. , Tardy I. , Lerch R.
Published: December 2017

The pattern of substrate utilization may influence postischemic myocardial injury. To characterize the effect of nutritional state on substrate selection and contractile function during control conditions and postischemic reperfusion, hearts from fed and fasted rats were perfused retrogradely with 0.4 mM palmitate, 8 mM glucose, and 175 mU/l insulin. Under control conditions, hearts from fasted rats exhibited lower glucose oxidation (-59%) and higher palmitate oxidation (+191%) than hearts from fed rats. During reperfusion, postischemic hearts exhibited stimulation of glucose-oxidation, with no difference between hearts from fasted and fed rats. However, oxidation of palmitate remained higher after fasting (+68%). Hearts from fasted rats exhibited lower left ventricular diastolic pressure and higher left ventricular systolic pressure development during reperfusion. The results indicate that 1) substrate selection in myocardium is influenced by the nutritional state independently of substrate availability, 2) during postischemic reperfusion, inhibition of glucose oxidation is removed in hearts from fasted rats, whereas inhibition of fatty acid oxidation in hearts from fed rats is maintained, and 3) myocardial injury is lower after fasting.
Visualization of doxorubicin-induced oxidative stress in isolated cardiac myocytes
Authors: Sarvazyan N.
Published: December 2017

The paper presents high-resolution fluorescence images obtained using laser-scanning confocal microscopy. Isolated cells from adult rat hearts were preloaded with 2',7'-dichlorofluorescin (an oxidant-sensitive fluorescent probe) and exposed to doxo- rubicin, an important anticancer drug with prominent cardioxicity. Fluorescence images were collected from live cells simultaneously on two channels: 1) 515-530 nm emission range was used to monitor an increase in dichlorofluorescein, the oxidized product of dichlorofluorescein, and 2) emission > 610 nm was used to visualize the intracellular distribution of doxorubicin. The images reveal intracellular oxidation close to the mitochondria after only 20 min of exposure of isolated cardiomyocytes to 40-160 microM doxorubicin. The data confirm an oxidative mechanism of doxorubicin cardiotoxicity and demonstrate the capability of a new technique to monitor intracellular oxidation in living cardiomyocytes.
Low PO2 inhibits calcium channel activity in arterial smooth muscle cells
Authors: Franco-Obregon A. , Lopez-Barneo J.
Published: December 2017

We studied the effect of O2 tension (PO2) on the activity of voltage-gated Ca2+ channels recorded in whole cell patch-clamped smooth muscle cells enzymatically dispersed from rabbit cerebral, celiac, femoral, and main pulmonary arteries, as well as from the porcine coronary artery. In all myocyte classes examined, a reduction of PO2 (hypoxia) produced a rapid and reversible inhibition of the macroscopic L-type Ca2+ current of similar general characteristics. The hypoxic inhibition of Ca2+ channel activity closely followed the time course of bath exchange, first becoming apparent at below approximately 80 mmHg PO2. The interaction of O2 with the Ca2+ channels was strongly voltage dependent. At -30 mV the average extent of current inhibition was approximately 80%; however, no effect or even potentiation of current amplitude was observed at potentials more positive than +30 mV. Hypoxia selectively slowed activation kinetics (approximately 1.5 times at -20 mV); however, channel deactivation and inactivation were unaltered by low PO2. In addition, hypoxia produced a reversible shift (8.1 +/- 1.0 mV, n = 12) of the Ca2+ conductance-voltage curve toward positive membrane potentials. We propose that the O2 sensitivity of Ca2+ channels may contribute to the well-known hypoxic dilatation of systemic and the main pulmonary arteries.
Changes in angiotensin II receptor density and calcium handling during proliferation in SHR aortic myocytes
Authors: Cortes S. F. , Lemos V. S. , Corriu C. , Stoclet J. C.
Published: December 2017

The aim of the present work was to characterize angiotensin II (ANG II) receptors and their effect on intracellular free Ca2+ concentration ([Ca2+]i) in proliferating aortic smooth muscle cells (VSMCs) from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). Independently from the proliferating state of cultures, apparent affinities of ligands (ANG II > losartan > > CGP-42112A) were consistent with the presence of AT1 receptors in primary cells from SHR and WKY. In proliferating cultures, increases in [Ca2+]i elicited by ANG II (100 nM) were dramatically attenuated or abolished in VSMCs from both strains compared with confluent and postconfluent cultures. Ca2+ releases induced by ionomycin and by ANG II in the absence of extracellular Ca2+ were also impaired in proliferating cultures. In addition, no significant strain difference was found in proliferating cultures with respect to ANG II receptor density, basal [Ca2+]i, and ANG II-induced increases in [Ca2+]i. However, ANG II receptor density significantly increased in SHR, but not in WKY VSMCs at postconfluence. Furthermore, basal [Ca2+]i was elevated in confluent and postconfluent cultures from SHR but not WKY. In confluent cultures, ANG II- and ionomycin-induced Ca2+ releases were enhanced in SHR VSMCs compared with WKY VSMCs. These results show that ANG II-induced Ca2+ release and ionomycin-sensitive Ca2+ stores are enhanced in SHR VSMCs but dramatically decreased in proliferating VSMC cultures from both strains. Mechanisms underlying these alterations remain to be defined. However, the results suggest that alterations in ANG II AT1 receptor density and in intracellular Ca2+ handling in confluent and postconfluent cultures are not associated with the proliferative phenotype of SHR VSMCs. In addition, no evidence for any change in ANG II receptor subtype associated with proliferation of VSMCs was found in either strain.
Derivation of the ascending aortic-carotid pressure transfer function with an arterial model
Authors: Karamanoglu M. , Feneley M. P.
Published: December 2017

To devise a method of deriving the ascending aortic pressure waveform from the noninvasively determined carotid arterial waveform, ascending aortic and carotid arterial pressures were recorded in 13 patients aged 58.5 +/- 10.0 (SD) yr. A single viscoelastic tube terminated with a modified windkessel was used to model the carotid arterial system. For each patient the model parameters, characteristic impedance of the tube (Z0), reflection coefficient at the termination (gamma), and time constant of the windkessel (tau), were estimated by minimizing the root-mean-square error between the measured and predicted carotid waveforms, with the ascending aortic pressure waveform as input. The resulting arterial parameters were realistic: Z0 = 729.5 +/- 246.8 dyn.s.cm-3, gamma = 0.75 +/- 0.19, and tau = 0.16 +/- 0.17 s. A generalized model constructed with these mean parameters yielded a smaller error between predicted and measured carotid arterial pressures (3.4 +/- 1.3 mmHg) than between ascending aortic pressure and measured carotid arterial pressure (4.4 +/- 1.6 mmHg, P < 0.01) and also reproduced the carotid wave contour indexed by the ratio of late systolic to early systolic peak amplitude: predicted = 1.26 +/- 0.05 and measured = 1.24 +/- 0.16 vs. aortic = 1.55 +/- 0.19.
Exogenous effects and endogenous production of endothelin in cardiac myocytes: potential significance in heart failure
Authors: Thomas P. B. , Liu E. C. , Webb M. L. , Mukherjee R. , Hebbar L. , Spinale F. G.
Published: December 2017

Increased plasma concentrations of endothelin have been identified in patients and animals with severe congestive heart failure (CHF). However, whether and to what extent increased endothelin (ET) concentrations influence left ventricular (LV) myocyte contractility, ET-receptor subtype density, and endogenous ET production with the development of CHF remains unclear. Accordingly, myocyte contractile function, response to ET, sarcolemmal ET-receptor density, and myocyte ET production were examined in pigs following the development of pacing-induced CHF (240 beats/min, 3 wk, n = 8) and in controls (n = 8). With CHF, plasma ET increased over threefold. In the presence of ET (10-500 pM), myocyte contractility increased in a dose-dependent manner in control myocytes but decreased in CHF myocytes. For example, in the presence of 200 pM ET, velocity of shortening increased by 32.8 +/- 2.3 microns/s in controls but decreased by 8.3 +/- 2.2 microns/s with CHF. LV sarcolemmal ET-receptor density was primarily of the ETA-receptor subtype in controls (96 +/- 1.0%) and was unchanged with CHF. In quiescent myocyte preparations, control myocytes secreted ET (2.29 +/- 0.45 amol.cell-1.h-1), which was similar in CHF myocytes. These findings suggest that the production of ET may have important and potentially differential effects on contractile function with the development of CHF.
Lysophosphatidylcholine transduces Ca2+ signaling via the platelet-activating factor receptor in macrophages
Authors: Ogita T. , Tanaka Y. , Nakaoka T. , Matsuoka R. , Kira Y. , Nakamura M. , Shimizu T. , Fujita T.
Published: December 2017

To clarify the molecular mechanism underlying the lysophosphatidylcholine (LPC) signaling, we studied the effect of LPC on the intracellular free calcium concentration ([Ca2+]i) in murine peritoneal macrophages. LPC when added alone induced biphasic elevation of [Ca2+]i, which consisted of a rapid increase followed by sustained elevation. LPC, when added with equimolar cholesterol, induced only the rapid increase in [Ca2+]i, which was blocked by WEB-2086, a selective platelet-activating factor (PAF) receptor antagonist. These results suggest LPC exerts a specific Ca2+ signaling. The sustained elevation reflected the cell lysis. Furthermore, we confirmed its pathway in a more specific manner using cloned PAF receptors expressed in Chinese hamster ovary cells. LPC induced an elevation of [Ca2+]i in a concentration-dependent manner only when the PAF receptor had been expressed, and the elevation of [Ca2+]i was blocked by WEB-2086. Taken together, LPC transduces Ca2+ signaling via the PAF receptor. Activation of the PAF receptor by LPC may indicate its novel important role in the pathogenesis of atherosclerosis.
Pulmonary microvascular reflection coefficients estimated with modified lymphatic washdown technique
Authors: Drake R. E. , Dhother S. , Gabel J. C.
Published: December 2017

Many investigators have used the lymphatic protein washdown technique to estimate the pulmonary microvascular membrane reflection coefficient to protein (sigma d). With that technique, the investigator causes a high microvascular filtration rate then estimates sigma d from the lymph and plasma protein concentrations. However the lymph may contain protein washed from the lung tissue, and the tissue protein may cause investigators to underestimate sigma d. Plasma protein osmotic pressure (IIc) may cause investigators to underestimate sigma d because IIc opposes fluid filtration. To minimize the effect of IIc, we decreased IIc to 5.6 +/- 1.1 mmHg in five anesthetized sheep. We increased the microvascular filtration rate by increasing pulmonary microvascular pressure to 22 +/- 3 mmHg. Then we tagged plasma protein with Evans blue dye and estimated sigma d from the lymph and plasma dye concentrations. Because tissue protein was not tagged, it did not interfere with our sigma d estimate. Our sigma d estimate (0.79 +/- 0.08) was much higher than previous estimates in anesthetized animals.
Chronic opiate-receptor inhibition in experimental congestive heart failure in dogs
Authors: Yatani A. , Imai N. , Himura Y. , Suematsu M. , Liang C. S.
Published: December 2017

Acute administration of opiate-receptor antagonists has previously been shown to improve cardiac output aortic blood pressure, systolic ventricular performance, and the baroreflex function in conscious dogs with right-sided congestive heart failure (RHF). However, whether similar changes occur after chronic opiate-receptor inhibition in congestive heart failure is not known. To determine the chronic effects of opiate-receptor antagonism on RHF, we administered naltrexone (200 mg/day), a long-acting, orally active opiate-receptor blocking agent, to RHF and sham-operated animals for 6 wk. Naltrexone had no effects on resting heart rate, right atrial pressure, aortic pressure, or cardiac output in RHF dogs but increased the first derivative of right and left ventricular pressure with respect to time (dP/dt) at rest and improved the dP/dt response to isoproterenol. The inotropic responses to isoproterenol and forskolin in isolated right ventricular trabeculate muscle also were improved by chronic naltrexone in RHF. Myocardial beta-receptor density was reduced in the failing right ventricle compared with the control (58 +/- 3 vs. 108 +/- 6 fmol/mg protein, P < 0.01) but was unaffected by addition of naltrexone. Finally, naltrexone prevented the decline in baroreflex sensitivity that occurred in RHF (-0.2 +/- 0.5 vs. -6.0 +/- 0.5 ms/mmHg, P < 0.01). These effects of naltrexone did not occur in the shamoperated animals. Chronic opiate-receptor blockade with naltrexone attenuates the development of reduced adrenergic inotropic responsiveness and baroreflex subsensitivity that occur in RHF. Because there was a similar improvement in the forskolin response in the absence of significant alterations in myocardial beta-adrenoceptor density after naltrexone treatment, the improvement in adrenergically mediated inotropic effects probably is mediated via a postreceptor mechanism.
Continuous low-dose NO inhalation does not prevent monocrotaline-induced pulmonary hypertension in rats
Authors: Maruyama J. , Maruyama K. , Mitani Y. , Kitabatake M. , Yamauchi T. , Miyasaka K.
Published: December 2017

We determined whether vasodilator doses of inhaled nitric oxide (NO) prevented the progression of pulmonary hypertension (PH) and vascular changes in monocrotaline-induced PH. Short-term NO inhalation in rats 3 wk after the injection of monocrotaline reduced mean pulmonary artery pressure (PAP) from 30.7 +/- 2.2 (SE) to 26.4 +/- 1.4 mmHg at 10 parts per million (ppm) and from 30.2 +/- 1.3 to 25.8 +/- 1.4 mmHg at 40 ppm. There were no differences among rats exposed to air only and rats exposed to 10 ppm of NO for 19 days after a single subcutaneous injection of monocrotaline, in mean PAP (34.3 +/- 1.9 mmHg air vs. 32.8 +/- 1.4 mmHg NO), right ventricular hypertrophy (RVH), medial wall thickness (MWT) of muscular arteries, and the percentage of muscularized arteries at alveolar wall (%AW) and duct (%AD) level. Additional groups exposed to air only and 40 ppm of NO for 19 days again showed no difference in mean PAP, RVH, MWT, and %AD, except that this dose slightly reduced %AW (60.6 +/- 3.4% air vs. 46.9 +/- 5.2% NO, P = 0.04). Urine nitrate (NO3) level was higher in rats that had inhaled NO. In contrast to chronic hypoxic PH, vasodilator doses of NO inhalation did not prevent the development of PH in this malignant form of experimental PH.
Purine nucleotides and phospholipids in ischemic and reperfused rat skeletal muscle: effect of ascorbate
Authors: Lagerwall K. , Madhu B. , Daneryd P. , Schersten T. , Soussi B.
Published: December 2017

The effect of intravenously administered ascorbate on the ischemic and reperfused rat skeletal muscle was investigated. Purine nucleotides and phospholipids in skeletal muscle from rats subjected to 4 h of ischemia followed by 1-h reperfusion were analyzed by high-performance liquid chromatography. In addition, ATP, phosphocreatine (PCr), Pi, and phosphomonoesters (PME) were analyzed by 31P-nuclear magnetic resonance at 202.4 MHz, and individual PME such as glucose-6-phosphate and IMP were quantified. PCr and ATP were exhausted after 4 h of ischemia and recovered poorly upon reperfusion in the soleus and tibialis muscle of untreated rats. Postischemic reperfusion resulted in significant loss of cardiolipin. Treatment with 55 mM ascorbate resulted in total restoration of PCr during reperfusion, and ATP recovered to 42% of control in the soleus. Recovery was improved in the tibialis as well, and the cardiolipin decrease was limited. A lower ascorbate concentration (5 mM) did not enhance postischemic recovery. Our findings show that a high dose of ascorbate improves the energetic state of rat skeletal muscle during postischemic reperfusion, probably due to its antioxidant function.
Hemodynamic changes in pseudopregnancy in chronically instrumented conscious rats
Authors: Slangen B. F. , Out I. C. , Verkeste C. M. , Smits J. F. , Peeters L. L.
Published: December 2017

It is unclear whether the trophoblast is needed for the normal early-pregnancy hemodynamic adaptation. In this study we tested the hypothesis that the presence of trophoblast is not essential for the initial hemodynamic adaptation in pregnancy. To this end, we measured systemic hemodynamics in conscious pseudopregnant rats and compared the results with those obtained in a concomitantly studied control group of virgin rats as well as with a previously studied group of pregnant rats. The rats were studied daily from day 4 postmating until day 10 and on days 12, 14, 18, and 20. In pseudopregnant rats, cardiac output (CO) increased from day 5 onward, to 14 +/- 3% above the initial value by day 8. This rise in CO was entirely accomplished by a rise in stroke volume (21 +/- 4% by day 8). Mean arterial pressure did not change appreciably. Therefore, total peripheral resistance also decreased by 21 +/- 4% by day 8. Meanwhile, peak flow, aortic flow acceleration, and stroke work, indicators of myocardial performance, had increased, and the hematocrit had decreased (15 +/- 1% by day 8). Between day 10 and day 20 the hemodynamic parameters gradually returned to baseline. We conclude that systemic hemodynamic changes do take place in pseudopregnancy. They consist of a rise in CO by a rise in stroke volume, an increase in myocardial performance, and hemodilution. The observed changes closely resemble those in early normal pregnancy. Therefore, we accept our hypothesis that trophoblast is not essential for the initial hemodynamic changes in rat pregnancy.
Changes in myocardial fluid filtration are reflected in epicardial lymph pressure
Authors: VanTeeffelen J. W. , Merkus D. , Vergroesen I. , Spaan J. A.
Published: December 2017

The effect of increased fluid filtration on stopped-flow epicardial lymph pressure (P(lymph)), used as an indicator of myocardial interstitial volume, was investigated in the anesthetized open-chest dog. Histamine infusion resulted in an increased systolic peak in the P(lymph) signal together with an increase in diastolic P(lymph) in four of five animals. During reactive hyperemia, systolic and diastolic P(lymph) increased to 127 +/- 8 and 121 +/- 6.7% (mean +/- SE, n = 6) of control, respectively. Peak P(lymph) was approximately 15 s later than peak coronary blood flow and venous pressure (P(ven)). When P(ven) was transiently elevated to 367 +/- 72 (systolic) and 247 +/- 45% (diastolic) of control, P(lymph) increased to 132 +/- 12 and 120 +/- 5.5% of control. The time of response was similar for P(ven) and P(lymph) (t50 approximately 2 S). The increased systolic and diastolic P(lymph) can be explained by an increase in interstitial and lymph filling. It is concluded that changes in myocardial fluid filtration are reflected in epicardial P(lymph). Furthermore, it seems that cardiac contraction constitutes an important defense mechanism against the formation of myocardial edema.