bluuebunny/crossref_metadata_2025 huggingface dataset:
Ischemic preconditioning translocates PKC-δ and -ε, which mediate functional protection in isolated rat heart
Authors: Kawamura Shuji , Yoshida Ken-Ichi , Miura Toshiro , Mizukami Yoichi , Matsuzaki Masunori
Published: December 2017

Protein kinase C (PKC) plays an important role in mediating ischemic preconditioning (PC). However, the relationship between PKC isoforms and PC is still uncertain. We analyzed subcellular localization of PKC isoforms by Western blot analysis in isolated rat heart and demonstrate that PKC-α, -δ, and -ε were translocated to the membrane fraction associated with the improvement of cardiac function. Translocation of PKC-δ and -ε persisted after a 30-min period following PC, but the translocation of PKC-α was transient. Under low Ca2+perfusion (0.2 mmol/l), PC improved the cardiac function associated with the translocation of PKC-δ. Chelerythrine (1.0 μmol/l) suppressed the translocation of all PKC isoforms associated with the loss of improvement of the cardiac function. On the other hand, bisindolylmaleimide (0.1 μmol/l) did not inhibit the improvement of cardiac function induced by PC, which was associated with the translocation of PKC-ε. These results indicate that the effect of PC on cardiac function is mediated by the translocation of either PKC-δ or -ε independently in rat hearts.
Endothelial defect mediates attenuated vasorelaxant response to isoproterenol after lung transplantation
Authors: Yoshida Kenichi , Flavahan Nicholas A. , Horibe Mayumi , Smedira Nicholas G. , Murray Paul A.
Published: December 2017

We have previously demonstrated that pulmonary vasodilation in response to isoproterenol is attenuated in conscious dogs after left lung autotransplantation (LLA). Our present goal was to identify the cellular mechanism responsible for this dysfunction. Size- and position-matched pulmonary arterial rings were isolated from the right (control) and left (LLA) lungs of 23 dogs 1–14 mo post-LLA. The rings were suspended for isometric tension recording and precontracted, and the vasorelaxant responses to activators of the β-adrenoreceptor signaling pathway were examined. With the endothelium intact the maximal pulmonary vasorelaxant response to isoproterenol was reduced ( P < 0.02) to 57 ± 9% in LLA rings, compared with 87 ± 3% in control rings. Responses to the Gsprotein activator cholera toxin were also attenuated post-LLA, with the concentration-effect curve shifted to the right ( P < 0.01) and no change in the maximal response. In contrast, the vasorelaxant responses to forskolin (adenylyl cyclase activator) or dibutyryl cAMP were similar in endothelium-intact control and LLA rings. In endothelium-denuded rings the maximal vasorelaxant responses to isoproterenol were reduced ( P < 0.01) to ∼25% in both control and LLA rings. In denuded rings cholera toxin, forskolin, and dibutyryl cAMP caused 100% vasorelaxation, and the IC50values for these agonists were similar in control and LLA rings. Isoproterenol increased ( P < 0.05) tissue cAMP to the same extent in control and LLA rings with or without endothelium. In contrast, isoproterenol increased ( P< 0.05) tissue cGMP only in endothelium-intact rings, and this effect was reduced ( P < 0.05) ∼50% in LLA rings compared with control. Oxypurinol (endothelial xanthine oxidase inhibitor) restored the pulmonary vasorelaxant response to isoproterenol in endothelium-intact LLA rings. Our results provide the first evidence that activation of the β-adrenoreceptor signaling pathway in endothelium-intact pulmonary arterial rings results in an increase in cGMP. Moreover, the attenuation in β-adrenoreceptor-mediated pulmonary vasorelaxation post-LLA is due to inactivation of nitric oxide by endothelium-derived superoxide anion.
Inhibition of baroreflex vagal bradycardia by nasal stimulation in rats
Authors: Kobayashi Masayoshi , Cheng Zhi Bin , Nosaka Shoichiro
Published: December 2017

Nasal stimulation provokes hypertension and bradycardia. We report here that such stimulation inhibits baroreflex vagal bradycardia (BVB). In chloralose- and urethan-anesthetized, β-adrenergic receptor-blocked rats, the aortic depressor nerves were cut and electrically stimulated to induce BVB. Nasal application of smoke, warm distilled water, or cold or hot Ringer solution suppressed BVB, but application of warm Ringer solution did not. Smoke-induced inhibition was abolished by trigeminal but not olfactory denervation. Neither suprapontine decerebration nor C3 spinal cord transection affected the inhibition. Bradycardia induced by electrical stimulation of the peripheral cut end of the cervical vagus nerve (VIB) was suppressed by long-lasting smoke application. Intravenous prazosin, a proposed blocker of prejunctional inhibition of acetylcholine release from the vagus terminals, abolished VIB inhibition but attenuated BVB inhibition only slightly. Thus nasal stimulation inhibits BVB, and this inhibition is mediated exclusively by the trigeminal nerve and occurs principally at the pontomedullary level, although the potential exists for contribution of the prejunctional mechanism. The inhibition of BVB might contribute to cardiovascular regulation associated with protection from atmospheric hazards.
Preserved hypocapnic pial arteriolar constriction during hyperammonemia by glutamine synthetase inhibition
Authors: Hirata Takahiko , Kawaguchi Tetsu , Brusilow Saul W. , Traystman Richard J. , Koehler Raymond C.
Published: December 2017

Ammonia intoxication, which results in astrocytic edema and glutamine accumulation, blocks cerebral vasodilation during hypercapnia but not during hypoxia. Ammonia’s effect on blood flow during hypocapnia is unclear, with some brain regions showing a paradoxical increase in flow. Here, we studied the responses to hypocapnia of pial arterioles not surrounded by astrocytic end feet to avoid mechanical compression by local edema. Blood flow was measured by microspheres in pentobarbital sodium-anesthetized rats equipped with closed cranial windows that permitted intravital microscopy. The normal pial arterial constriction in hypocapnia (12 ± 1%; mean ± SE) was blocked (2 ± 1%) during a 6-h intravenous infusion of ammonium acetate, with some regions (cerebrum, midbrain) showing increased flow during hypocapnia. After pretreatment with methionine sulfoximine (MSO), which inhibits glutamine synthesis, the normal hypocapnic constrictor response was retained in pial arterioles (11 ± 2%) during hyperammonemia. The increase in the calculated cerebrovascular resistance also was retained. An analog of MSO that does not block glutamine synthesis (buthionine sulfoximine) was ineffective in maintaining hypocapnic reactivity. In a sodium acetate-treated control group, MSO did not alter the pial arteriolar response. Normal vasoconstrictive ability was shown during ammonium infusion in response to U-46619, a thromboxane analog. We conclude that the inhibition of hypocapnic responsivity induced by ammonium is not due to paralysis of the pial arteriolar smooth muscle or to vascular compression by swollen astrocytes but is in some way due to glutamine metabolically produced from the ammonium.
Modulation of repolarization in rabbit Purkinje and ventricular myocytes coupled by a variable resistance
Authors: Huelsing Delilah J. , Spitzer Kenneth W. , Cordeiro Jonathan M. , Pollard Andrew E.
Published: December 2017

Purkinje-ventricular junctions (PVJs) have been implicated as potential sites of arrhythmogenesis, in part because of the dispersion of action potential duration (APD) between Purkinje (P) and ventricular (V) myocytes. To characterize electrotonic modulation of APD as a function of junctional resistance ( Rj), we coupled single isolated rabbit P and V myocytes with an electronic circuit. In seven of eight PV myocyte pairs, both APDs shortened on coupling at Rj= 50 MΩ. This was in contrast to modulation of APD in paired ventricular myocytes, which demonstrated APD shortening of the intrinsically longer action potential and APD prolongation of the intrinsically shorter action potential. Companion computer simulations, performed to suggest possible mechanisms for the paradoxical shortening of the V action potential in paired P and V myocytes, showed that the difference in intrinsic peak plateau potentials ( Vpp) of the P and V myocytes determined whether the V action potential shortened or prolonged on coupling. This difference in Vppcaused a large, repolarizing coupling current to flow to the V myocyte, contributing to early inactivation of the L-type calcium current and early activation of the inward rectifier current. These results suggest that intrinsic differences in phase 1 repolarization could yield differing patterns of APD shortening or prolongation in the network of subendocardial PVJs, leaving some PVJs vulnerable to conduction of premature stimuli while other PVJs remain refractory.
Downward gradient in action potential duration along conduction path in and around the sinoatrial node
Authors: Boyett M. R. , Honjo H. , Yamamoto M. , Nikmaram M. R. , Niwa R. , Kodama I.
Published: December 2017

Regional differences in electrical activity in rabbit sinoatrial node have been investigated by recording action potentials throughout the intact node or from small balls of tissue from different regions. In the intact node, action potential duration was greatest at or close to the leading pacemaker and declined markedly in all directions from it, e.g., by 74 ± 4% (mean ± SE, n = 4) to the crista terminalis. Similar data were obtained from the small balls. The gradient is down the conduction pathway and will help prevent reentry. In the intact node, a zone of inexcitable tissue with small depolarizations of <25 mV or stable resting potentials was discovered in the inferior part of the node, and this will again help prevent reentry. The intrinsic pacemaker activity of the small balls was slower in tissue from more inferior (as well as more central) parts of the node [e.g., cycle length increased from 339 ± 13 ms ( n = 6) to 483 ± 13 ms ( n = 6) in transitional tissue from more superior and inferior sites], and this may help explain pacemaker shift.
Orally administered NHE1 inhibitor cariporide reduces acute responses to coronary occlusion and reperfusion
Authors: Humphreys Rachael A. , Haist James V. , Chakrabarti Subrata , Feng Qingping , Arnold J. Malcolm O. , Karmazyn Morris
Published: December 2017

Na+/H+exchange (NHE) mediates myocardial ischemic and reperfusion injury. We examined the effects of dietary administration of the potent and selective NHE1 inhibitor cariporide on acute responses to coronary artery ligation and reperfusion in the anesthetized rat. Male Sprague-Dawley rats received control rat chow or an identical diet containing 3 parts per million of cariporide for 1 wk before 225 min of occlusion of the left main coronary artery or 45 min of occlusion followed by 180 min of reperfusion. Hearts were excised and divided into left ventricle, right ventricle, and interventricular septum for analysis of NHE1 mRNA expression and apoptosis by staining with terminal deoxynucleotidyl transferase-mediated nick end labeling. Ischemia and reperfusion were associated with a threefold elevation in NHE1 mRNA expression in control animals that was significantly reduced in cariporide-fed rats. Cariporide reduced mortality from 26% of animals to 0%. The incidence of all arrhythmias was significantly reduced, including ventricular fibrillation (from 42 to 0%) and ventricular tachycardia (from 81 to 15%), as well as the number of ventricular premature beats (from 70 ± 12 to 17 ± 6). Cariporide moderately reduced apoptosis only in the reperfused left ventricle to values not significantly greater than those in sham-operated animals, and this was associated with a significantly higher ratio of Bcl-2 to Bax. This study suggests that NHE inhibition with dietary cariporide represents an effective management of acute postinfarction responses.
Chemotactic, mitogenic, and angiogenic actions of UTP on vascular endothelial cells
Authors: Satterwhite Christina M. , Farrelly Angela M. , Bradley Michael E.
Published: December 2017

Endothelial cells express receptors for ATP and UTP, and both UTP and ATP elicit endothelial release of vasoactive compounds such as prostacyclin and nitric oxide; however, the distinction between purine and pyrimidine nucleotide signaling is not known. We hypothesized that UTP plays a more important role in endothelial mitogenesis and chemotaxis than does ATP and that UTP is angiogenic. In cultured endothelial cells from guinea pig cardiac vasculature (CEC), both UTP and vascular endothelial growth factor (VEGF) were significant mitogenic and chemotactic factors; in contrast, ATP demonstrated no significant chemotaxis in CEC. In chick chorioallantoic membranes (CAM), UTP and VEGF treatments produced statistically significant increases in CAM vascularity compared with controls. These findings are the first evidence of chemotactic or angiogenic effects of pyrimidines; they suggest a role for pyrimidine nucleotides that is distinct from those assumed by purine nucleotides and provide for the possibility that UTP serves as an extracellular signal for processes such as endothelial repair and angiogenesis.
Charybdotoxin and apamin block EDHF in rat mesenteric artery if selectively applied to the endothelium
Authors: Doughty Joanne M. , Plane Frances , Langton Philip D.
Published: December 2017

In rat mesenteric artery, endothelium-derived hyperpolarizing factor (EDHF) is blocked by a combination of apamin and charybdotoxin (ChTX). The site of action of these toxins has not been established. We compared the effects of ChTX and apamin applied selectively to the endothelium and to the smooth muscle. In isometrically mounted arteries, ACh (0.01–10 μm), in the presence of indomethacin (2.8 μM) and N ω-nitro-l-arginine methyl ester (l-NAME) (100 μM), concentration dependently relaxed phenylephrine (PE)-stimulated tone (EC50 50 nM; n = 10). Apamin (50 nM) and ChTX (50 nM) abolished this relaxation ( n = 5). In pressurized arteries, ACh (10 μM), applied intraluminally in the presence of indomethacin (2.8 μM) andl-NAME (100 μM), dilated both PE-stimulated (0.3–0.5 μM; n = 5) and myogenic tone ( n = 3). Apamin (50 nM ) and ChTX (50 nM) applied intraluminally abolished ACh-induced dilatations. Bath superperfusion of apamin and ChTX did not affect ACh-induced dilatations of either PE-stimulated ( n = 5) or myogenic tone ( n = 3). This is the first demonstration that ChTX and apamin act selectively on the endothelium to block EDHF-mediated relaxation.
Phospholamban-to-SERCA2 ratio controls the force-frequency relationship
Authors: Meyer Markus , Bluhm Wolfgang F. , He Huaping , Post Steven R. , Giordano Frank J. , Lew Wilbur Y. W. , Dillmann Wolfgang H.
Published: December 2017

The force-frequency relationship (FFR) describes the frequency-dependent potentiation of cardiac contractility. The interaction of the sarcoplasmic reticulum Ca2+-adenosinetriphosphatase (SERCA2) with its inhibitory protein phospholamban (PLB) might be involved in the control of the FFR. The FFR was analyzed in two systems in which the PLB-to-SERCA2 ratio was modulated. Adult rabbit cardiac myocytes were transduced with adenovirus encoding for SERCA2, PLB, and β-galactosidase (control). After 3 days, the relative PLB/SERCA2 values were significantly different between groups (SERCA2, 0.5; control, 1.0; PLB, 4.5). SERCA2 overexpression shortened relaxation by 23% relative to control, whereas PLB prolonged relaxation by 39% and reduced contractility by 47% (0.1 Hz). When the stimulation frequency was increased to 1.5 Hz, myocyte contractility was increased by 30% in control myocytes. PLB-overexpressing myocytes showed an augmented positive FFR (+78%), whereas SERCA2-transduced myocytes displayed a negative FFR (−15%). A more negative FFR was also found in papillary muscles from SERCA2 transgenic mice. These findings demonstrate that the ratio of phospholamban to SERCA2 is an important component in the control of the FFR.
Peripheral muscle ergoreceptors and ventilatory response during exercise recovery in heart failure
Authors: Francis Noelle , Cohen-Solal Alain , Logeart Damien
Published: December 2017

Recent studies have suggested that the increased ventilatory response during exercise in patients with chronic heart failure was related to the activation of muscle metaboreceptors. To address this issue, 23 patients with heart failure and 7 normal subjects performed arm and leg bicycle exercises with and without cuff inflation around the arms or the thighs during recovery. Obstruction slightly reduced ventilation and gas exchange variables at recovery but did not change the kinetics of recovery of these parameters compared with nonobstructed recovery: half-time of ventilation recovery was 175 ± 54 to 176 ± 40 s in patients and 155 ± 66 to 127 ± 13 s in controls ( P < 0.05, patients vs. controls, not significant within each group from baseline to obstructed recovery). We conclude that muscle metaboreceptor activation does not seem to play a role in the exertion hyperventilation of patients with heart failure.
Osmotic shock: modulation of contractile function, pHi, and ischemic damage in perfused guinea pig heart
Authors: Befroy Douglas E. , Powell Trevor , Radda George K. , Clarke Kieran
Published: December 2017

To determine the contribution of changes in extracellular osmolarity to ischemic injury, isolated guinea pig hearts were perfused with hyposmotic (220 mosM) or hyperosmotic (380 mosM) buffer.31P NMR spectroscopy was used to follow changes in intracellular pH (pHi) and energetics. Hyposmotic buffer decreased myocardial developed pressure by 30 ± 2% and pHiby 0.02 ± 0.01 unit, whereas hyperosmotic buffer increased myocardial developed pressure by 34 ± 1% and pHiby 0.14 ± 0.01 unit. All hearts recovered to control values on restoration of isosmotic (300 mosM) buffer. The hyperosmolar-induced intracellular alkalosis and developed pressure increase were not prevented by inhibition of Na+/H+exchange with use of 1 μM HOE-642 but were abolished with use of bicarbonate-free buffers. After 20 min of total global ischemia, hearts perfused with hyposmotic buffer showed significantly greater recoveries of developed pressure, phosphocreatine, and ATP than control hearts, but hearts perfused with hyperosmotic buffer did not recover after ischemia. In conclusion, buffer osmolarities between 220 and 380 mosM alter myocardial pHiand developed pressure but are not deleterious during perfusion. However, buffer osmolarity significantly alters the extent of myocardial ischemic injury.
Phase-dependent heartbeat modulation by muscle contractions during dynamic handgrip in humans
Authors: Niizeki Kyuichi , Miyamoto Yoshimi
Published: December 2017

The influence of cardiac phase on the response of the cardiac pacemaker to dynamic hand contraction in eight healthy young men was studied to determine whether heart rate response to muscle contraction varied as a function of timing within the cardiac cycle. Changes in R-R interval (RRI) in response to muscle contraction were measured at various cardiac phases during heartbeat-synchronized handgrip at a rate of one contraction per two heartbeats. To extract the direct effect of the muscle contraction on the RRI, spontaneous slow variations and respiratory sinus arrhythmia were removed from the total RRI fluctuations in the frequency domain. Cross-correlograms between the extracted RRI fluctuations and muscle contraction showed that the coupling was strong when the muscle contraction occurred at the middle phase of the cardiac cycle. Muscle contraction at the systolic phase of the cardiac cycle had a tendency to produce a phase advance (shortening of RRI), whereas muscle contraction at the middle phase or later had a tendency to produce a phase delay (prolongation of RRI). The results showed the presence of a neuronal circuit that modulates the cardiac pacemaker activity depending on the timing of muscle contraction in the cardiac cycle.
Aging-dependent depression in the kinetics of force development in rat skinned myocardium
Authors: Fitzsimons Daniel P. , Patel Jitandrakumar R. , Moss Richard L.
Published: December 2017

Normal aging of the rodent heart results in prominent prolongation of the twitch. We tested the hypothesis that increased expression of β-myosin heavy chain (MHC), as occurs in the normal aging process in the rodent heart, contributes to the prolongation of the twitch by depressing the kinetics of cross-bridge interaction. Using 3-, 9-, 21-, and 33-mo-old male Fischer 344 × Brown Norway F1hybrid rats, we examined both the rate of tension development ( kCa) and unloaded shortening velocity in chemically skinned myocardium. Although kCain all four age groups was dependent on the level of Ca2+activation, both submaximal and maximal kCawere significantly slower in 9-, 21-, and 33-mo-old rats relative to 3-mo-old rats. Furthermore, unloaded shortening velocity was significantly reduced in 9-, 21-, and 33-mo-old rats compared with 3-mo-old rats. Collectively, these data strongly suggest that the aging-related increase in β-MHC expression results in a progressive slowing of cross-bridge interaction kinetics in skinned myocardium, which most likely contributes to the overall aging-dependent reduction in myocardial functional capacity.
Early response kinase and PI 3-kinase activation in adult cardiomyocytes and their role in hypertrophy
Authors: Schlüter Klaus-Dieter , Simm Andreas , Schäfer Matthias , Taimor Gerhild , Piper Hans Michael
Published: December 2017

The present study investigated the role of early response kinase (ERK) and phosphatidylinositol 3 (PI 3)-kinase in ventricular cardiomyocytes from adult rat for the hypertrophic response to α-adrenoceptor stimulation. Parameters of the hypertrophic response were stimulation of protein synthesis and induction of creatine kinase BB. The α-adrenoceptor agonist phenylephrine (10 μmol/l) activated ERK2 and PI 3-kinase. The protein kinase C inhibitor bisindolylmaleimide (5 μmol/l) and the mitogen-activated protein kinase kinase inhibitor PD-98059 (10 μmol/l) but not the tyrosine kinase inhibitor genistein (100 μmol/l) blocked ERK2 activation. Inhibition of ERK2 activation abolished induction of creatine kinase BB by phenylephrine but not the increase in protein synthesis. The PI 3-kinase inhibitor wortmannin (100 nmol/l) blocked protein synthesis under α-adrenoceptor stimulation but did not interfere with ERK2 activation. Inhibition of the ERK2 pathway with PD-98059 did not affect PI 3-kinase activation. We conclude that ERK2- and PI 3-kinase-dependent pathways represent two mutually exclusive ways of signaling that lead to different aspects of the hypertrophic response to α-adrenoceptor stimulation.
Cardiac myofibrillar and sarcoplasmic reticulum function are not depressed in insulin-resistant JCR:LA-cprats
Authors: Misra Tarun , Gilchrist James S. C. , Russell James C. , Pierce Grant N.
Published: December 2017

Depressed myofibrillar Ca2+-ATPase activity and sarcoplasmic reticulum (SR) Ca2+uptake are important mechanisms that are responsible for the cardiac dysfunction exhibited by insulin-deficient (type I) diabetic animals. The JCR:LA- cp rat is a model for type II non-insulin-dependent diabetes mellitus (NIDDM). This rat is insulin resistant, obese, and has high levels of circulating glucose, cholesterol, insulin, and triglycerides. The purpose of this study was to determine whether changes in cardiac myofibrillar, SR, and cardiomyocyte function exist in this model of type II diabetes. Myofibrils and SR were isolated from hearts by differential centrifugation. Surprisingly, we found that myofibrillar Ca2+-ATPase activities were unaltered in these animals. Ca2+uptake in isolated SR fractions was increased in diabetic cp/ cprats, whereas Ca2+-ATPase activity and ryanodine binding were unchanged. Cardiomyocytes isolated from hearts of control and experimental animals had similar active cell shortening and intracellular Ca2+concentration under basal conditions and in response to caffeine. Our data argue against the presence of a cardiomyopathy in this diabetic model and suggest that insulin may be an important factor in the cardiomyopathy observed in type I diabetic models.
Characterization of a newly found stretch-activated KCa,ATP channel in cultured chick ventricular myocytes
Authors: Kawakubo Takashi , Naruse Keiji , Matsubara Tatsuaki , Hotta Nigishi , Sokabe Masahiro
Published: December 2017

With the use of the patch-clamp technique, five kinds of stretch-activated (SA) ion channels were identified on the basis of their single-channel conductances and ion selectivities in cultured chick ventricular myocytes. Because a high-conductance K+-selective channel predominated among these channels, we concentrated on characterizing its properties mostly using excised inside-out patches. With 145 mM KCl solution in the pipette and the bath, the channel had a conductance of 199.8 ± 8.2 pS ( n = 22). The ion selectivities among K+, Na+, Ca2+, and Cl− as estimated from their permeability ratios were P Na/ P K= 0.03, P Ca/ P K= 0.025, and P Cl/ P K= 0.026. The probability of the channel being open (Po) increased with the Ca2+concentration in the bath ([Ca2+]b; dissociation constant K d = 0.51 μM at +30 mV) and membrane potential (voltage at half-maximal Po= 39.4 mV at 0.35 μM [Ca2+]b). The channel was blocked by gadolinium, tetraethylammonium, and charybdotoxin from the extracellular surface and, consequently, was identified as a Ca2+-activated K+(KCa) channel type. The channel was also reversibly activated by ATP applied to the intracellular surface ( K d = 0.74 mM at 0.10 μM [Ca2+]bat +30 mV). From these data taken together, we concluded that the channel is a new type of KCachannel that could be designated as an “SA KCa,ATP channel.” To our knowledge, this is the first report of KCa channel in heart cells.
Angiotensin II and mechanical stretch induce production of tumor necrosis factor in cardiac fibroblasts
Authors: Yokoyama Tomoyuki , Sekiguchi Kenichi , Tanaka Toru , Tomaru Koichi , Arai Masashi , Suzuki Tadashi , Nagai Ryozo
Published: December 2017

To determine whether ANG II as well as mechanical stress affect the production of tumor necrosis factor (TNF) in the heart, neonatal rat cardiac myocytes and fibroblasts were cultured separately and treated for 6 h with ANG II, lipopolysaccharide (LPS), or cyclic mechanical stretch. LPS induced the production of TNF in cardiac myocytes and fibroblasts. However, TNF synthesis in fibroblasts was 20- to 40-fold higher than in myocytes. ANG II (≥10−8M) and mechanical stretch stimulated the production of TNF in cardiac fibroblasts but not in myocytes. Furthermore, both ANG II and LPS increased the expression of TNF-α mRNA in cardiac fibroblasts. Isoproterenol inhibited both LPS- and ANG II-induced production of TNF in cardiac fibroblasts with increasing intracellular cAMP level. Moreover, both isoproterenol and dibutyryl cAMP inhibited LPS-induced TNF-α mRNA expression. Thus activation of the renin-angiotensin system, as well as mechanical stress, can stimulate production of TNF in cardiac fibroblasts. Furthermore, β-adrenergic receptors may be responsible for the regulation of TNF synthesis at the transcriptional level by elevating intracellular cAMP.
Cardiovascular phenotype and temperature control in mice lacking thyroid hormone receptor-β or both α1 and β
Authors: Johansson Catarina , Göthe Sten , Forrest Douglas , Vennström Björn , Thorén Peter
Published: December 2017

We have used a telemetry system to record heart rate, body temperature, electrocardiogram (ECG), and locomotor activity in awake, freely moving mice lacking thyroid hormone receptor (TR)-β or TR-α1 and -β (TR-α1/β). The TR-α1/β-deficient mice had a reduced heart rate compared with wild-type controls. The TR-β-deficient mice showed an elevated heart rate, which, however, was unresponsive to thyroid hormone treatment regardless of hormonal serum levels. ECG revealed that the TR-β-deficient mice had a shortened Q-Tend time in contrast to the TR-α1/β-deficient mice, which exhibited prolonged P-Q and Q-Tend times. Mental or pharmacological stimulation of the sympathetic nervous system resulted in a parallel increase in heart rate in all animals. A single injection of a nonselective β-adrenergic-receptor blocker resulted in a parallel decrease in all mice. The TR-α1/β-deficient mice also had a 0.4°C lower body temperature than controls, whereas no difference was observed in locomotor activity between the different strains of mice. Our present and previous results support the hypothesis that TR-α1 has a major role in determining heart rate under baseline conditions and body temperature and that TR-β mediates a hormone-induced increase in heart rate.
Cannabinoid CB1 receptor of cat cerebral arterial muscle functions to inhibit L-type Ca2+ channel current
Authors: Gebremedhin Debebe , Lange Andrew R. , Campbell William B. , Hillard Cecilia J. , Harder David R.
Published: December 2017

The CB1 subtype of the cannabinoid receptor is present on neurons in the brain and mediates the perceptual effects of Δ9-tetrahydrocannabinol and other cannabinoids. We found that cat cerebral arterial smooth muscle cells (VSMC) contain the protein for the CB1 receptor and express a cDNA that has >98% amino acid homology to the CB1 cDNA expressed in rat and human neurons. Activation of the CB1 cannabinoid receptor has been shown to decrease the opening of N-type voltage-gated Ca2+ channels in neurons through a pertussis toxin-sensitive GTP-binding protein. In the present study we tested the hypothesis that activation of the cannabinoid CB1 receptor in cerebral VSMC inhibits voltage-gated Ca2+ channels and results in cerebral vasodilation. The predominant Ca2+ current identified in cat cerebral VSMC is a voltage-gated, dihydropyridine-sensitive, L-type Ca2+ current. The cannabimimetic drug WIN-55,212-2 (10–100 nM) induced concentration-dependent inhibition of peak L-type Ca2+ current, which reached a maximum of 82 ± 4% at 100 nM ( n = 14). This effect was mimicked by the putative endogenous CB1-receptor agonist anandamide, which produced a concentration-related reduction of peak L-type Ca2+ current with a maximum inhibition (at 300 nM) of 39 ± 4% ( n = 12). The inhibitory effects of both ligands on peak L-type Ca2+currents were abolished by pertussis toxin pretreatment and application of the CB1-receptor antagonist SR-141716A (100 nM, n = 5). Both WIN-55,212-2 and anandamide produced concentration-dependent relaxation of preconstricted cerebral arterial segments that was abolished by SR-141716A. These results indicate that the CB1 receptor is expressed in cat cerebral VSMC and that the cerebral vasculature is one of the targets for endogenous cannabinoids. These findings suggest that the CB1 receptor and its endogenous ligand may play a fundamental role in the regulation of cerebral arterial tone and reactivity by modulating the influx of Ca2+ through L-type Ca2+ channels.
Rapid tachyphylaxis to hemodynamic effects of PACAP-27 after inhibition of nitric oxide synthesis
Authors: Whalen Erin J. , Travis Mark D. , Johnson Alan Kim , Lewis Stephen J.
Published: December 2017

The vasodilator effects of pituitary adenylate cyclase-activating polypeptide (PACAP)-27 are subject to tachyphylaxis in rats treated with the nitric oxide (NO) synthase inhibitor NG-nitro-l-arginine methyl ester (l-NAME). We examined whether this tachyphylaxis could be prevented by administration of the putative endothelium-derived nitrosyl factor S-nitroso-l-cysteine (l-SNC) and whetherl-SNC may exert its effects via increases in cGMP levels in vascular smooth muscle. Five doses of PACAP-27 (2 nmol/kg iv) produced pronounced vasodilator responses in saline-treated rats. These responses were not subject to tachyphylaxis. The first injection of PACAP-27 (2 nmol/kg iv) inl-NAME-treated (50 μmol/kg iv) rats produced vasodilator responses similar to those in saline-treated rats, whereas subsequent injections produced progressively smaller responses. The injection ofl-SNC (1,200 nmol/kg iv) before each injection of PACAP-27 prevented tachyphylaxis to the Gsprotein-coupled receptor agonist in l-NAME-treated rats, whereas equihypotensive doses of the NO donor sodium nitroprusside (100 μg/kg iv) did not. The injection of the membrane-permeant cGMP analog 8-(4-chlorophenylthio)guanosine 3′,5′-cyclic monophosphate (8-CPT-cGMP; 30 μmol/kg iv) tol-NAME-treated rats restored resting hemodynamic values to pre-l-NAME levels but did not prevent the development of tachyphylaxis to PACAP-27. These results suggest that nitrosyl factors prevent the development of tachyphylaxis to the hemodynamic actions of PACAP-27. These nitrosyl factors may act independently of their ability to generate cGMP in vascular smooth muscle.
Transmural microcirculatory blood flow distribution in right and left ventricular free walls of rabbits
Authors: Matsumoto Takeshi , Ebata Jun , Tachibana Hiroyuki , Goto Masami , Kajiya Fumihiko
Published: December 2017

Within-layer regional myocardial flows in the left and right ventricles (LV, RV) and in LV with increased myocardial workload (β1-adrenoceptor stimulation) were studied transmurally in anesthetized rabbits. Myocardial flow distribution was visualized with resolutions between 0.1 × 0.1- and 1 × 1-mm2 pixels, using digital radiography combined with the3H-labeled desmethylimipramine deposition technique. The spatial pattern of flow distribution was quantitated by the coefficient of variation of regional flows (CV, related to global flow heterogeneity) and the correlation between adjacent regional flows (CA, inversely related to local flow randomness). CV was lower in LV than in RV [ P < 0.05, nonparametric 2-way analysis of variance (NANOVA)]. When resolution was lowered from 0.1 × 0.1- to 1 × 1-mm2 pixels, CV decreased by 70% in both LV and RV. CA was higher in LV than in RV ( P < 0.05, NANOVA); the interventricular difference in CA was large over the resolutions between 0.4 × 0.4- and 1 × 1-mm2 pixels. In LV, both CV and CA increased with depth of myocardium ( P < 0.05, NANOVA); in subendocardium CV was high comparable with CV in RV ( P = 0.47, NANOVA). The enhancement of myocardial workload decreased CV and tended to decrease CA in LV subendocardium ( P < 0.05, P = 0.06, respectively; NANOVA). We conclude that 1) microregional flow distribution is less heterogeneous and less random in LV than in RV; 2) transmurally, in LV subendocardium global flow heterogeneity was the highest whereas local flow randomness was the lowest, so that clusters of low- or high-flow regions exist in this LV layer; and 3) global flow heterogeneity decreased and local flow randomness tended to increase (flow homogenizing occurred) in LV subendocardium with increasing myocardial workload. Thus the distributed pattern of myocardial microregional flows may be adaptable to local myocardial metabolic change.
Insulin-induced endothelin release and vasoreactivity in hypertriglyceridemic and hypertensive rats
Authors: Nava Pilar , Guarner Verónica , Posadas Rosalinda , Pérez Israel , Baños Guadalupe
Published: December 2017

Insulin-elicited endothelin release in hypertriglyceridemic, hypertensive, hyperinsulinemic (HTG) rats was shown. Weanling male Wistar rats were given 30% sucrose in their drinking water for 20–24 wk. In vitro contractions of aorta and femoral arteries were elicited with 40 mM KCl. Endothelin release induced with KCl plus 50 μU/ml insulin resulted in increases in contractile responses: 41 ± 5.9 and 57 ± 6% for control and 65.5 ± 6 and 95 ± 9% for HTG aortas and femoral arteries, respectively. The endothelin ETB-receptor blocker BQ-788 decreased responses to KCl + insulin by 39 ± 8 and 53 ± 5% in control and 48 ± 13 and 79 ± 3.5% in HTG aortas and femoral arteries, respectively. The ETA-receptor antagonist PD-151242 inhibited these responses by 12 ± 10 and 1 ± 9% in control and by 51.5 ± 9 and 58.5 ± 1% in HTG aortas and femoral arteries, respectively. These results suggest that endothelin may contribute to the hypertension in this model.
O2cost of contractility but not of mechanical energy increases with temperature in canine left ventricle
Authors: Mikane Takeshi , Araki Junichi , Suzuki Shunsuke , Mizuno Ju , Shimizu Juichiro , Mohri Satoshi , Matsubara Hiromi , Hirakawa Masahisa , Ohe Tohru , Suga Hiroyuki
Published: December 2017

We investigated the effects of myocardial temperature on left ventricular (LV) mechanoenergetics in the excised, cross-circulated canine heart. We used the framework of the LV contractility ( Emax)-pressure-volume area (PVA; a measure of total mechanical energy)-myocardial oxygen consumption (Vo2) relationship. We have shown this framework to be useful to integrative analysis of the mechanoenergetics of a beating heart. In isovolumic contractions at a constant pacing rate, increasing myocardial temperature from 30 to 40°C depressed Emaxand increased the oxygen cost of Emax, which was enhanced by dobutamine, in a linear manner. However, the slope of the Vo2-PVA relation (reciprocal of contractile efficiency) and its Vo2intercept remained constant. Q10values of Emax, the oxygen cost of Emax, and the oxygen cost of PVA were 0.4, 2.1 and 1.0, respectively, around normothermia. We conclude that the temperature-dependent processes of cross-bridge cycling and Ca2+handling integratively depress Emaxand augment its oxygen cost without affecting the oxygen cost of PVA as myocardial temperature increases by 10°C around normothermia.
Failure of cdc2 promoter activation and G2/M transition by ANG II and AVP in vascular smooth muscle cells
Authors: Fujita Nobuya , Furukawa Yusuke , Itabashi Naoki , Tsuboi Yasushi , Matsuda Michio , Okada Koji , Saito Toshikazu
Published: December 2017

The physiological role of the vasoconstrictive hormones arginine vasopressin (AVP) and angiotensin II (ANG II) in the development of vascular hyperplasia is still unclear. We examined the effects of these hormones on cell cycle regulation of cultured rat vascular smooth muscle cells (VSMC). AVP and ANG II were able to induce G1/S transition and DNA synthesis in serum-starved quiescent VSMC but failed to promote further progression into G2/M phases. AVP and ANG II enhanced the expression and activity of cdk2, cyclin E, and proliferating cell nuclear antigen but did not induce expression of cdc2/cyclin B complex, a critical regulator of G2/M transition. The failure of cdc2 mRNA induction was found to be caused by a defect in cdc2 promoter activation. Binding of free E2F-1 to the cdc2 promoter did not occur in hormone-treated VSMC, which may account for the defective induction of cdc2. The absence of cdc2 promoter activation and G2/M transition may be important for the prevention of hyperplasia under physiological conditions but underlies the hypertrophy of VSMC.
Contribution of endogenous endothelin to large epicardial coronary artery tone in dogs and humans
Authors: Thorin Éric , Parent Robert , Ming Zhi , Lavallée Michel
Published: December 2017

Nitric oxide (NO) may normally impair endothelin (ET) activity in epicardial coronary arteries. Lifting this inhibitory feedback could reveal ET-dependent effects involving ETA- and/or ETB-receptor activation. In conscious dogs, the blockade of ETA receptors (intracoronary Ro-61–1790) increased external circumflex coronary artery diameter (CD) (sonomicrometry) by 0.10 ± 0.01 from 3.04 ± 0.12 mm ( P < 0.01) without altering coronary blood flow (Doppler). Similarly, CD increased (0.09 ± 0.01 from 2.91 ± 0.14 mm; P < 0.01) when Ro-61–1790 was given after blockade of NO formation with intracoronary N ω-nitro-l-arginine methyl ester (l-NAME). In contrast, ETB-receptor blockade (intracoronary Ro-46–8443) did not influence baseline CD with and without l-NAME. In vitro, increases in tension caused by N ω-nitro-l-arginine (l-NNA) or PGF2α in arterial rings were reduced by ETA- but not ETB-receptor blockade. ETA-receptor blockade also reduced the increase in tension caused byl-NNA in human coronary arterial rings. Thus ETA receptors, but not ETB receptors, account for ET-dependent constriction in canine epicardial coronary arteries in vivo. ET-dependent effects were independent of the level of NO formation in vitro and in vivo. In human epicardial coronary arterial rings, ETA-receptor blockade also caused significant relaxation.
Fourier analysis of fluctuations of oxygen tension and blood flow in R3230Ac tumors and muscle in rats
Authors: Braun Rod D. , Lanzen Jennifer L. , Dewhirst Mark W.
Published: December 2017

Tumor hypoxia is a major barrier to tumor radiation therapy. Typically tumor hypoxia occurs in two forms: chronic and acute. Although the existence of acute hypoxia has long been acknowledged, its temporal characteristics have never been directly measured and documented. In this study tumor[Formula: see text], blood flow (BF), and arterial blood pressure (BP) were measured simultaneously in nine Fischer 344 rats bearing R3230Ac rat mammary adenocarcinomas in the subcutis of the left hindleg. We measured [Formula: see text] at a single location for 36–125 min using recessed-tip oxygen microelectrodes. Simultaneously, we measured tumor BF at two sites within the tumor using laser-Doppler flowmetry (LDF). Similar recordings were made in the quadriceps muscle of seven non-tumor-bearing rats. The [Formula: see text], tumor BF, and BP records were subjected to Fourier analysis.[Formula: see text] and BF showed low-frequency fluctuations (<2 cycles/min) in both tumor and muscle, but the magnitude of the changes in tumor was greater. Tumor BF showed more activity at low frequencies than muscle BF, and the magnitude tended to be greater. No strong correlations were found between[Formula: see text] and BF power spectra for either tumor or muscle or between the frequency patterns of BP and tumor[Formula: see text] spectra. These results quantitatively demonstrate, for the first time, that BF and[Formula: see text] fluctuate at very low frequencies in tumors. In addition to having biological significance for tumor therapy, these fluctuations may have the potential to alter tumor cell behavior via induction of hypoxia reoxygenation injury and/or altered gene expression.
Cytosolic redox state mediates postischemic response to pyruvate dehydrogenase stimulation
Authors: White Lawrence T. , O’Donnell J. Michael , Griffin Julian , Lewandowski E. Douglas
Published: December 2017

Augmented pyruvate oxidation via pharmacological stimulation of pyruvate dehydrogenase (PDH) during reperfusion has been related to improved recovery of postischemic hearts independent of glycolytic activity. This study examined recovery of postischemic rabbit hearts during activation of PDH with dichloroacetate (DCA) in the presence of lactate, as a source of pyruvate, to determine the response to substrate-dependent changes in cytosolic redox state. After 10 min of ischemia, isolated hearts were reperfused with either 2.5 mM or 0.5 mM pyruvate (Pyr) or 2.5 mM lactate (Lac), with or without 5 mM DCA.13C-enriched substrates allowed NMR assessment of metabolic perturbations. During normal perfusion, Pyr and Lac supported similar mechanical work. Increasing Pyr oxidation restored postischemic rate-pressure product to 82 ± 4 and 88 ± 6% of preischemic values during reperfusion with 2.5 and 0.5 mM Pyr, respectively, vs. 61 ± 6 and 45 ± 14% for untreated 2.5 and 0.5 mM Pyr, respectively ( P < 0.05). In contrast, increasing Lac oxidation did not benefit recovery of RPP in untreated (44 ± 7%) vs. DCA-treated 36 ± 4% hearts. Thus the benefit of PDH activation for contractile recovery of postischemic hearts is mediated by the source of pyruvate, which also influences cytosolic redox state.
Reperfusion-induced changes in capillary perfusion and filtration: effects of hypercholesterolemia
Authors: Harris Norman R.
Published: December 2017

Fluid filtration rate ( J v/ S) and red blood cell velocity ( V RBC) in individual mesenteric capillaries of normocholesterolemic (NC) and hypercholesterolemic (HC) rats were measured before and after ischemia and reperfusion (I/R). In NC rats, a correlation was found between baseline J v/ Sand the percent of the feeding arteriole length that was paired (<15 μm) with a postcapillary venule (A-V pairing), but not in the HC group. Additionally, in NC rats only, a correlation was found between baseline V RBC and A-V pairing. In capillaries in which A-V pairing was substantial (>20%), V RBCdropped after reperfusion in the HC group (54% of baseline; P < 0.05), but not in the NC group (79%). The decrease in V RBC in HC rats could be attenuated by a P-selectin antibody (PB1.3). PB1.3 was also able to attenuate the increase in I/R-induced capillary J v/ Sin HC rats (median increase = 1.26-fold vs. 1.53-fold without PB1.3). These data suggest a role for A-V pairing in capillary perfusion in NC rats and a potential role for P-selectin in I/R-induced microvascular dysfunction in HC rats.
Identification of specific EP receptors responsible for the hemodynamic effects of PGE2
Authors: Audoly Laurent P. , Tilley Stephen L. , Goulet Jennifer , Key Mikelle , Nguyen Mytrang , Stock Jeffrey L. , McNeish John D. , Koller Beverly H. , Coffman Thomas M.
Published: December 2017

To identify the E-prostanoid (EP) receptors that mediate the hemodynamic actions of PGE2, we studied acute vascular responses to infusions of PGE2using lines of mice in which each of four EP receptors (EP1through EP4) have been disrupted by gene targeting. In mixed groups of males and females, vasodepressor responses after infusions of PGE2were significantly diminished in the EP2−/− and EP4−/− lines but not in the EP1−/− or EP3−/− lines. Because the actions of other hormonal systems that regulate blood pressure differ between sexes, we compared the roles of individual EP receptors in males and females. We found that the relative contribution of each EP-receptor subclass was strikingly different in males from that in females. In females, the EP2and EP4receptors, which signal by stimulating adenylate cyclase, mediate the major portion of the vasodepressor response to PGE2. In males, the EP2receptor has a modest effect, but most of the vasodepressor effect is mediated by the phospholipase C-coupled EP1receptor. Finally, in male mice, the EP3receptor actively opposes the vasodepressor actions of PGE2. Thus the hemodynamic actions of PGE2are mediated through complex interactions of several EP-receptor subtypes, and the role of individual EP receptors differs dramatically in males from that in females. These differences may contribute to sexual dimorphism of blood pressure regulation.
Impaired cerebral vasodilator responses to NO and PDE V inhibition after subarachnoid hemorrhage
Authors: Sobey Christopher G. , Quan Lilly
Published: December 2017

Subarachnoid hemorrhage (SAH) is associated with impaired nitric oxide (NO)-mediated cerebral vasodilatation. We tested the hypothesis that SAH causes alterations in the production of, hydrolysis of, or responsiveness to cGMP in the rat basilar artery in vivo. Rats were injected with saline or autologous blood into the cisterna magna. Two days later, effects of vasoactive drugs on basilar artery diameter were examined using a cranial window preparation. Vasodilator responses to ACh, sodium nitroprusside (SNP), and low concentrations (≤10−5 M) of zaprinast, an inhibitor of phosphodiesterase V (PDE V), were impaired in SAH rats ( P < 0.05). In contrast, vasodilator responses to adenosine and 8-BrcGMP were similar in control and SAH rats. Vasoconstrictor responses to 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one, an inhibitor of soluble guanylate cyclase, were unaffected by SAH. In the presence of zaprinast (10−5–10−4 M), responses to ACh and SNP were equivalent in control and SAH rats. Thus an increased rate of cGMP hydrolysis by PDE V may be a major factor contributing to the impairment of NO-mediated cerebral vasodilatation after SAH.