bluuebunny/crossref_metadata_2025 huggingface dataset:
Reversal of permeability transition during recovery of hearts from ischemia and its enhancement by pyruvate
Authors: Kerr Paul M. , Suleiman M.-Saadeh , Halestrap Andrew P.
Published: December 2017

We have used mitochondrial entrapment of 2-deoxy-d-[3H]glucose (2-DG) to demonstrate that recovery of Langendorff-perfused rat hearts from ischemia is accompanied by reversal of the mitochondrial permeability transition (MPT). In hearts loaded with 2-DG before 40 min of ischemia and 25 min of reperfusion, 2-DG entrapment [expressed as 105× (mitochondrial 2-[3H]DG dpm per unit citrate synthase)/(total heart 2-[3H]DG dpm/g wet wt)] increased from 11.1 ± 1.3 (no ischemia, n = 4) to 32.5 ± 1.9 ( n = 6; P < 0.001). In other experiments, 2-DG was loaded after 25 min of reperfusion to determine whether some mitochondria that had undergone the MPT during the initial phase of reperfusion subsequently “resealed” and thus no longer took up 2-DG. The reduction of 2-DG entrapment to 20.6 ± 2.4 units ( n = 5) confirmed that this was the case. Pyruvate (10 mM) in the perfusion medium increased recovery of left ventricular developed pressure from 57.2 ± 10.3 to 98.9 ± 10.8% ( n = 6; P < 0.05) and reduced entrapment of 2-DG loaded preischemically and postischemically to 23.5 ± 1.5 ( n = 4; P < 0.001) and 10.5 ± 0.5 ( n = 4; P < 0.01) units, respectively. The presence of pyruvate increased tissue lactate content at the end of ischemia and decreased the effluent pH during the initial phase of reperfusion concomitant with an increase in lactate output. We suggest that pyruvate may inhibit the MPT by decreasing pHiand scavenging free radicals, thus protecting hearts from reperfusion injury.
Changes in resistance vessels during hemorrhagic shock and resuscitation in conscious hamster model
Authors: Sakai Hiromi , Hara Hiroyuki , Tsai Amy G. , Tsuchida Eishun , Johnson Paul C. , Intaglietta Marcos
Published: December 2017

The unanesthetized hamster dorsal skinfold preparation was used to monitor diameters and blood flow rates in resistance arteries (small arteries, A0: diameter, 156 ± 23 μm) and capacitance vessels (small veins, V0: 365 ± 64 μm), during 45 min of hemorrhagic shock at 40 mmHg mean arterial pressure (MAP) and resuscitation. A0 and V0 vessels constricted significantly to 52 and 70% of the basal values, respectively, whereas precapillary arterioles (A1–A4, 8–60 μm) and collecting venules (VC–VL, 26–80 μm) did not change or tended to dilate. Blood flow rates in the microvessels declined to <20% of the basal values. Resuscitation with shed autologous blood (SAB) showed incomplete recovery of A0 and V0 diameters even 2 h after resuscitation (71 ± 14% and 81 ± 18%, respectively, of basal value), whereas other vessels did not change significantly. The behavior of A0 diameter coincided with the incomplete recovery of blood flow rates in all the vessels (ca. 50%) according to Poiseuille’s law, and the incomplete recovery of functional capillary density (ca. 75%). Resuscitation with 8% human serum albumin in saline (HSA) tended to show higher levels of A0 constriction and A4 dilation and lowered blood flow rates. Resuscitation with SAB restored tissue[Formula: see text] 27 ± 10 mmHg after 2 h, which was near control levels (28 ± 5 mmHg), whereas resuscitation with HSA caused tissue [Formula: see text] to remain significantly depressed (6 ± 2 mmHg), and flow rates were significantly lower than resuscitation with SAB. These results indicate that response of the A0 vessels is the crucial determinant of blood flow in the observed area. The constriction of A0 may help sustain MAP, and constriction of V0 may enhance blood redistribution from the skin to the vital organs under the hypotensive condition.
β-Adrenergic modulation of L-type Ca2+-channel currents in early-stage embryonic mouse heart
Authors: Liu Weiran , Yasui Kenji , Arai Akiko , Kamiya Kaichiro , Cheng Jianhua , Kodama Itsuo , Toyama Junji
Published: December 2017

Little information is available concerning the modulation of cardiac function by β-adrenergic agonists in early-stage embryonic mammalian heart. We have examined the effects of isoproterenol (Iso) on the spontaneous beating rate and action potential (AP) configuration in embryonic mouse hearts at 9.5 days postcoitum (dpc), just 1 day after they started to beat. Iso (3 μM) increased the spontaneous beating rate in whole hearts, dissected ventricles, and isolated ventricular myocytes. In ventricular myocytes, Iso also increased the slope of the pacemaker potential and the action potential duration but decreased the maximum upstroke velocity. In whole cell voltage-clamp experiments, the Ca2+-channel currents were measured as Ba2+ currents ( I Ba). In 9.5-dpc myocytes, I Ba was enhanced significantly from −4.7 ± 0.9 to −6.7 ± 1.2 pA/pF (by 52.4 ± 14.8%, n = 10) after the application of Iso. Propranolol (3 μM) reversed the effect of Iso. Forskolin (For, 10 μM) produced an increase in I Ba by 95.5 ± 18.8% ( n = 8). In ventricular myocytes at a late embryonic stage (18 dpc), 3 μM Iso caused an appreciably greater increase in I Ba from −6.2 ± 0.5 to −14.5 ± 2.2 pA/pF (by 137.8 ± 33.0%, n = 8), whereas the increase in I Ba by 10 μM For (by 120.0 ± 23.0%, n = 7) was comparable to that observed in the early stage (9.5 dpc). These results indicate that the L-type Ca2+-channel currents are modulated by β-adrenergic receptors in the embryonic mouse heart as early as 9.5 dpc, probably via a cAMP-dependent pathway.
Maintenance of blood pressure in normotensive dogs by endothelin
Authors: Münter Klaus , Ehmke Heimo , Kirchengast Michael
Published: December 2017

The role of endothelin (ET)-1 in blood pressure homeostasis and the interaction with the renin-angiotensin system (RAS) was investigated in normotensive conscious dogs. ETAreceptors were blocked by LU-135252 (1–30 mg/kg); trandolapril (2 mg/kg) or losartan (10 mg/kg) was used to inhibit the RAS. LU-135252 in oral doses of 3–30 mg/kg significantly reduced mean arterial pressure (MAP) by ∼10 mmHg maximally, whereas trandolapril or losartan were without any effect. MAP reduction was more pronounced when LU-135252 was combined with either losartan (−15.5 ± 3.2 mmHg; 2 h postadministration; P < 0.05) or trandolapril (−30.9 ± 3.6 mmHg; P < 0.05). When endogenous nitric oxide (NO) generation was blocked but NO concomitantly infused, this synergistic effect on MAP was prevented. The data show that ET-1 contributes to the maintenance of blood pressure via ETA receptors. Furthermore, ET-1 and ANG II play a prominent role in the control of blood pressure by opposing the effects of NO. The pronounced blood pressure fall after combined blockade of ETA receptors and the RAS may be mediated by an enhanced release of NO.
Coronary vasodilator effects of BNP: mechanisms of action in coronary conductance and resistance arteries
Authors: Zellner Christian , Protter Andrew A. , Ko Eitetsu , Pothireddy Madhusudhan R. , DeMarco Teresa , Hutchison Stuart J. , Chou Tony M. , Chatterjee Kanu , Sudhir Krishnankutty
Published: December 2017

Brain natriuretic peptide (BNP), a hormone secreted predominantly in ventricular myocytes, may influence coronary vascular tone. We studied the coronary vasodilatory response to BNP under physiological conditions and after preconstriction with endothelin-1 (ET-1) in anesthetized pigs. Average peak-flow velocity (APV) was measured using intracoronary Doppler, and cross-sectional area (CSA) was measured using intravascular ultrasound. Coronary blood flow (CBF) was calculated. Intracoronary BNP induced dose-dependent increases in CSA, APV, and CBF similar in magnitude to those induced by nitroglycerin (NTG). The magnitude of BNP-induced vasodilation was accentuated after preconstriction with ET-1. Pretreatment with either the nitric oxide synthase inhibitor Nω-nitro-l-arginine methyl ester or the cyclooxygenase inhibitor indomethacin attenuated the coronary vasodilator effect of BNP in resistance arteries without influencing epicardial vasodilation. Pretreatment with the ATP-sensitive potassium-channel blocker glibenclamide enhanced epicardial vasodilation in response to BNP. We conclude that BNP exerts coronary vasodilator effects, predominantly in epicardial conductance vessels. An accentuated vasodilatory response to BNP occurs in ET-1-preconstricted arteries. BNP-induced vasodilation in coronary resistance arteries may be partially mediated via nitric oxide and/or prostaglandin release.
Contribution of L-type Ca2+current to electrical activity in sinoatrial nodal myocytes of rabbits
Authors: Verheijck E. Etienne , van Ginneken Antoni C. G. , Wilders Ronald , Bouman Lennart N.
Published: December 2017

The role of L-type calcium current ( I Ca,L) in impulse generation was studied in single sinoatrial nodal myocytes of the rabbit, with the use of the amphotericin-perforated patch-clamp technique. Nifedipine, at a concentration of 5 μM, was used to block I Ca,L. At this concentration, nifedipine selectively blocked I Ca,L for 81% without affecting the T-type calcium current ( I Ca,T), the fast sodium current, the delayed rectifier current ( I K), and the hyperpolarization-activated inward current. Furthermore, we did not observe the sustained inward current. The selective action of nifedipine on I Ca,L enabled us to determine the activation threshold of I Ca,L, which was around −60 mV. As nifedipine (5 μM) abolished spontaneous activity, we used a combined voltage- and current-clamp protocol to study the effects of I Ca,L blockade on repolarization and diastolic depolarization. This protocol mimics the action potential such that the repolarization and subsequent diastolic depolarization are studied in current-clamp conditions. Nifedipine significantly decreased action potential duration at 50% repolarization and reduced diastolic depolarization rate over the entire diastole. Evidence was found that recovery from inactivation of I Ca,L occurs during repolarization, which makes I Ca,L available already early in diastole. We conclude that I Ca,L contributes significantly to the net inward current during diastole and can modulate the entire diastolic depolarization.
Aortic pressure-diameter relationship assessed by intravascular ultrasound: experimental validation in dogs
Authors: Hardt Stefan E. , Just Armin , Bekeredjian Raffi , Kübler Wolfgang , Kirchheim Hartmut R. , Kuecherer Helmut F.
Published: December 2017

Intravascular ultrasound (IVUS) has emerged as an important diagnostic method for evaluating vessel diameter and vessel wall motion. To evaluate the validity of IVUS in assessing changes in the pressure-diameter relationship we compared measurements of abdominal aortic diameters derived from IVUS with those simultaneously obtained at the same site using implanted sonomicrometers in five chronically instrumented conscious dogs and in seven acutely instrumented anesthetized dogs. Five hundred eighty beats were analyzed to obtain peak systolic and end-diastolic diameters and to calculate aortic compliance at different blood pressure levels induced either by an aortic pneumatic cuff or by intravenous injections of nitroglycerin or norepinephrine. IVUS agreed closely with sonomicrometer measurements at different blood pressure levels. However, IVUS slightly but significantly underestimated aortic diameters by 0.6 ± 0.7 mm for systolic diameters ( P < 0.001) and by 0.7 ± 0.6 mm for diastolic diameters ( P < 0.001) compared with the sonomicrometer measurements. We conclude that IVUS is a feasible and reliable method to measure dynamic changes in aortic dimensions and has the potential to provide ready access to assess aortic compliance in humans.
Proapoptotic effects of ANG II in human coronary artery endothelial cells: role of AT1receptor and PKC activation
Authors: Li Dayuan , Yang Baichun , Philips M. Ian , Mehta Jawahar L.
Published: December 2017

Anoxia-reoxygenation, tumor necrosis factor-α (TNF-α), and angiotensin II (ANG II) have been shown to induce apoptosis in myocytes. However, the role of these mediators in causing apoptosis of human coronary artery endothelial cells (HCAEC) is not known. This study was designed to examine the interaction of these mediators in induction of apoptosis in HCAEC. Cultured HCAEC were exposed to anoxia-reoxygenation, TNF-α, and ANG II. TNF-α enhanced apoptosis of HCAEC (determined by DNA nick-end labeling in situ and DNA laddering) caused by anoxia-reoxygenation. ANG II increased apoptosis beyond that caused by anoxia-reoxygenation and TNF-α. Apoptosis caused by ANG II was reduced by losartan, a specific ANG II type 1 receptor (AT1R) blocker, whereas PD-123,177, a specific ANG II type 2 receptor blocker, under identical conditions had minimal effect. The proapoptotic effects of ANG II were associated with the activation of protein kinase C (PKC). The importance of PKC activation as a signal transduction mechanism became evident in experiments wherein treatment of HCAEC with a specific inhibitor of PKC activation decreased ANG II-mediated apoptosis. Thus AT1R activation appears to be responsible for apoptosis caused by ANG II in HCAEC, and AT1R activation-mediated apoptosis involves activation of PKC.
Constitutive expression of interleukin-1α precursor promotes human vascular smooth muscle cell proliferation
Authors: Beasley Debbie , Cooper Angela L.
Published: December 2017

Vascular smooth muscle cell (VSMC) proliferation plays a critical role in the failure of vascular surgeries and contributes to the development of atherosclerotic lesions. Evidence that interleukin-1 (IL-1) is a mitogen for cultured VSMC has implicated its release by activated macrophages in the development of atherosclerosis. VSMC also produce IL-1, including the precursor form of IL-1α. However, it is not known whether IL-1α precursor is processed to mature IL-1α or released from VSMC, nor is it known whether either precursor or mature IL-1α functions as an autocrine growth factor. The goals of the present study were to establish whether proliferation is enhanced in human VSMC transfectants producing IL-1α constitutively at levels comparable to those produced after activation, and to determine which domains of IL-1α are important for its activity. Human VSMC were stably transfected with expression vectors directing constitutive expression of either full-length IL-1α precursor [IL-1α-(1—271)], its NH2-terminal domain [IL-1α-(1—112)], or mature IL-1α [IL-1α-(113—271)]. Both IL-1α-(1—271) and IL-1α-(113—271) stable transfectants produced moderate levels of IL-1α (0.2–1.0 ng/106cells) and released low levels of IL-1α into the supernatant (<20 pg/ml). VSMC stably transfected with either IL-1α-(1—271) or IL-1α-(113—271) expression plasmids proliferated rapidly compared with nontransfected or vector-transfected VSMC and displayed a distinct morphology characterized by elongated, spindle-shaped cells. Stable transfection with IL-1α-(1—271) was somewhat more effective than transfection with IL-1α-(113—271). Interestingly, VSMC transfected with IL-1α-(113—271) expression plasmids also expressed IL-1α-(1—271) mRNA, suggesting that IL-1α-(113—271) activates an IL-1-induced IL-1 autocrine loop. In contrast, neither proliferation rates nor morphology was affected by stable transfection with IL-1α-(1—112) expression plasmids. Exogenous IL-1 receptor antagonist partially reversed the enhanced DNA synthesis in VSMC transfected with either IL-1α-(1—271) or IL-1α-(113—271) expression plasmids, suggesting that the pro-proliferative effect of VSMC-derived IL-1α is at least partially mediated by signaling via the type I IL-1 receptor. These results demonstrate that IL-1α precursor is an autocrine growth factor for human VSMC and further indicate that amino acids 113–271 play a crucial role in its actions.
Nitric oxide mediates sympathetic vasoconstriction at supraspinal, spinal, and synaptic levels
Authors: Iida Noriko
Published: December 2017

The purposes of this study were to investigate the level of the sympathetic nervous system in which nitric oxide (NO) mediates regional sympathetic vasoconstriction and to determine whether neural mechanisms are involved in vasoconstriction after NO inhibition. Ganglionic blockade (hexamethonium), α1-receptor blockade (prazosin), and spinal section at T1 were used to study sympathetic involvement. NO was blocked with N ω-nitro-l-arginine methyl ester (l-NAME). Regional blood flow in the mesenteric and renal arteries and terminal aorta was monitored by electromagnetic flowmetry in conscious rats.l-NAME (3–5 mg/kg iv) increased arterial pressure and peripheral resistance. Ganglionic blockade (25 mg/kg iv) significantly reduced the increase in resistance in the mesentery and kidney in intact and spinal-sectioned rats. Ganglionic blockade significantly decreased hindquarter resistance in intact rats but not in spinal-sectioned rats. Prazosin (200 μg/kg iv) significantly reduced the increased hindquarter resistance. We concluded that NO suppresses sympathetic vasoconstriction in the mesentery and kidney at the spinal level, whereas hindquarter tone is mediated at supraspinal and synaptic levels.
Epidermal growth factor: a potent vasoconstrictor in experimental hypertension
Authors: Florian Jennifer A. , Watts Stephanie W.
Published: December 2017

We have tested the hypothesis that growth factor signaling pathways are augmented in hypertension, a disease associated with vascular smooth muscle cell growth. Thoracic aorta was dissected from deoxycorticosterone acetate-salt (DOCA-salt) and one kidney, one clip (1K, 1C) hypertensive rats and from sham normotensive rats for use in isolated tissue bath experiments. Systolic blood pressure was significantly higher in DOCA-salt and 1K, 1C than in normotensive sham rats: 192 ± 7, 185 ± 10, and 117 ± 4 mmHg, respectively. Although virtually no contraction to epidermal growth factor (EGF) was observed in endothelium-denuded sham rat aorta [1 ± 1% phenylephrine (PE) (10 μmol/l)-induced contraction], the maximal EGF-induced contraction was 45 ± 7% in endothelium-denuded aorta from DOCA-salt hypertensive rats and 39 ± 7% in aorta from 1K, 1C rats. Although slightly attenuated, a contraction to EGF was still observed in endothelium-intact aortic strips from 28-day DOCA-salt hypertensive rats. We also conducted concentration-response curves to EGF on days 1, 3, 5, 7, 14, and 21 of DOCA-salt therapy. A significant contraction to EGF in aorta from DOCA-salt rats was observed on day 14, when DOCA-salt rats had significantly higher blood pressure than sham rats: 188 ± 6 and 122 ± 3 mmHg, respectively. Transforming growth factor-α, an agonist of the EGF receptor, contracted DOCA-salt rat aorta (30 ± 7% PE-induced contraction) but not sham aorta (3 ± 3%). The EGF receptor tyrosine kinase inhibitor 4,5-dianilinophthalimide (10 μmol/l), the mitogen-activated protein kinase kinase inhibitor PD-098059 (10 μmol/l), and the L-type voltage-gated calcium channel inhibitor diltiazem (1 mol/l), but not the cyclooxygenase inhibitor indomethacin (10 μmol/l), virtually abolished EGF-induced contraction (85, 98, and 99% reduction, respectively). These data support a striking difference in EGF signaling between normotensive and hypertensive animals. Furthermore, they provide evidence that growth factors should be considered vasoconstrictors as well as growth modulators in hypertension.
Phospholamban deficiency does not compromise exercise capacity
Authors: Desai Kavin H. , Schauble Eric , Luo Wusheng , Kranias Evangelia , Bernstein Daniel
Published: December 2017

Deficiency of phospholamban (PLB) results in enhancement of basal murine cardiac function and an attenuated response to β-adrenergic stimulation. To determine whether the absence of PLB also reduces the reserve capacity of the murine cardiovascular system to respond to stress, we evaluated the heart rate (HR), blood pressure, and metabolic responses of PLB-deficient (PLB−/−) mice to graded treadmill exercise (GTE). PLB−/− mice were hypertensive at rest (125 ± 19 vs. 109 ± 16 mmHg, P < 0.05) but had normal tachycardic and hypotensive responses to isoproterenol. The HR response to GTE was normal; however, the hypertension in PLB−/− mice normalized at peak exercise. Their exercise capacities, as measured by duration of exercise and peak oxygen consumption (V˙o 2), were normal. The oxygen pulse (V˙o 2/HR) curve was also normal in PLB−/− mice, suggesting an ability to appropriately increase stroke volume and oxygen extraction during GTE, despite an inability to increase β-adrenergically stimulated cardiac contractility. Thus deficiency of PLB, although resulting in diminished β-adrenergic inotropic reserve, does not compromise cardiac performance during exercise.
Expression of endothelin-1, ETAand ETBreceptors, and ECE and distribution of endothelin-1 in failing rat heart
Authors: Kobayashi Tsutomu , Miyauchi Takashi , Sakai Satoshi , Kobayashi Masahiko , Yamaguchi Iwao , Goto Katsutoshi , Sugishita Yasuro
Published: December 2017

Endothelin (ET)-1 has a positive inotropic effect and induces hypertrophy in cardiomyocytes. We previously reported that the peptide level of ET-1 is increased in the failing heart of rats with chronic heart failure (CHF) and that treatment with an ETA-receptor antagonist greatly improves survival in rats with CHF. However, precise analysis for alteration of the myocardial ET system in the failing heart is not known. In this study, we used rats with CHF due to chronic myocardial infarction. Sham-operated rats served as a control. The results showed that the level of preproendothelin (preproET)-1 mRNA and the peptide level of ET-1 were markedly increased in the heart of rats with CHF, whereas the expression of endothelin-converting enzyme (ECE)-1 mRNA in the heart did not differ between CHF and control rats. The intensity of ET-1 staining (ET-1-like immunoreactivity) in cardiomyocytes was markedly stronger in rats with CHF than in control rats, and the fibrotic tissues of the infarcted area were not stained. The mRNA and protein levels of both ETAand ETBreceptors in the heart were significantly higher in rats with CHF than in control rats. The present study suggests that the increase in ET-1 peptide level in the heart of the rats with CHF originated from upregulation of preproET-1 mRNA, which was not attendant with the alteration of ECE-1 mRNA expression, and that both the ETA- and ETB-receptor systems are greatly accelerated in the failing heart.
Arterial chemoreflex in conscious normotensive and hypertensive adult rats
Authors: Hayward Linda F. , Johnson Alan Kim , Felder Robert B.
Published: December 2017

Evidence from human and animal studies suggests that the arterial chemoreflex may be exaggerated in essential hypertension. In the present study, cardiorespiratory responses to peripheral chemoreceptor stimulation were compared in conscious unrestrained spontaneously hypertensive (SH) and normotensive Wistar-Kyoto (WKY) and Sprague-Dawley (SD) rats (13–14 wk old). Chemoreceptors were stimulated by injections of potassium cyanide (30–125 μg/kg iv). Chemoreceptor stimulation elicited a pressor response and bradycardia. The peak change in mean arterial pressure evoked during chemoreceptor stimulation was not significantly different between SH ( n= 18) and WKY ( n = 18) rats but was significantly smaller in SD rats ( n = 18). An evaluation of respiratory responses to chemoreceptor stimulation in conscious and anesthetized rats also demonstrated no significant difference between SH and WKY rats, but the response of the SD rats tended to be smaller. These results demonstrate that differences in the arterial chemoreflex response of SH vs. normotensive rats are not linked to hypertension but, rather, to differences between rat strains.
Importance of PKC and tyrosine kinase in single or multiple cycles of preconditioning in rat hearts
Authors: Fryer Ryan M. , Schultz Jo El J. , Hsu Anna K. , Gross Garrett J.
Published: December 2017

Both tyrosine kinase (TK) and protein kinase C (PKC) inhibitors have been shown individually to completely abolish the cardioprotective effects of ischemic preconditioning (IPC) in rabbits; however, blockade of both enzymes is necessary to totally abolish IPC in pigs. Recently, we have shown that TK inhibition partially attenuates the cardioprotective effect of IPC in intact rat hearts. Therefore, the present study was designed to test the hypothesis that inhibition of both TK and PKC is necessary to completely abolish IPC in the intact rat and that this effect is dependent on the intensity of the preconditioning stimulus. All animals were subjected to 30 min of coronary artery occlusion and 2 h of reperfusion. In series 1, multiple-cycle-induced IPC was produced via three 5-min occlusions interspersed with 5 min of reperfusion (3 × 5 IPC). Genistein (5 mg/kg), a TK inhibitor infused 30 min before IPC, and chelerythrine chloride (5 mg/kg), a PKC inhibitor infused 5 min before the prolonged ischemic insult, were administered alone or in combination in the absence or presence of 3 × 5 IPC. 3 × 5 IPC produced a marked reduction in infarct size as a percentage of area at risk compared with control (8.0 ± 0.8 vs. 56.1 ± 0.8%). The effects of 3 × 5 IPC were partially blocked by pretreatment with genistein (34.0 ± 2.0%) or chelerythrine (26.4 ± 2.8%) alone; however, combined administration of genistein and chelerythrine completely abolished the effects of 3 × 5 IPC (50.7 ± 3.6%). In series 2, single-cycle IPC was elicited by one 5-min occlusion followed by 10 min of reperfusion (1 × 5 IPC). Compared with control, 1 × 5 IPC also significantly reduced infarct size (15.4 ± 3.0%). Genistein or chelerythrine administered alone completely abolished 1 × 5 IPC-induced cardioprotection. These results suggest that the efficacy of TK and PKC inhibition to block IPC depends on the intensity of the preconditioning stimulus and that these kinases may work through parallel pathways.
Angiotensin II exacerbates lipopolysaccharide-induced contractile depression in rabbit cardiac myocytes
Authors: Yasuda Satoshi , Lew Wilbur Y. W.
Published: December 2017

In sepsis, lipopolysaccharide (LPS) depresses cardiac function by inducing production of nitric oxide (NO) and its second messenger cGMP. LPS also stimulates ANG II production. We hypothesized that ANG II modulates the cardiac response to LPS. Adult rabbit cardiac myocytes incubated with LPS (10 ng/ml) had increased cardiac cGMP after 6 h (but not within 1 h) [527 ± 43 vs. 316 ± 27 (SE) fmol/mg protein in controls, n = 16 each group, P < 0.05]. This was associated with depressed cell shortening with no alterations in Ca2+transients (indo 1 fluorescence), indicating a decreased myofilament responsiveness to Ca2+. ANG II (100 nM) alone had no effect. However, ANG II with LPS produced higher cGMP levels (1,025 ± 113 fmol/mg protein, n = 16, P < 0.05 vs. LPS alone), more severe contractile depression, impaired Ca2+handling, and decreased mitochondrial activity (MTS assay). We conclude that ANG II and LPS have synergistic effects on the activation of NO-cGMP pathways to induce dose-dependent impairments in excitation-contraction coupling in cardiac myocytes.
Glutamatergic projection to RVLM mediates suppression of reflex bradycardia by parabrachial nucleus
Authors: Len Wen-Bin , Chan Julie Y. H.
Published: December 2017

We investigated the role of glutamatergic projection from the parabrachial nucleus (PBN) complex to the rostral ventrolateral medulla (RVLM) in the PBN-induced suppression of reflex bradycardia in adult Sprague-Dawley rats that were maintained under pentobarbital anesthesia. Under stimulus conditions that did not appreciably alter the baseline systemic arterial pressure and heart rate, electrical (10-s train of 0.5-ms pulses, at 10–20 μA and 10–20 Hz) or chemical (l-glutamate, 1 nmol) stimulation of the ventrolateral regions and Köelliker-Fuse (KF) subnucleus of the PBN complex significantly suppressed the reflex bradycardia in response to transient hypertension evoked by phenylephrine (5 μg/kg iv). The PBN-induced suppression of reflex bradycardia was appreciably reversed by bilateral microinjection into the RVLM of the N-methyl-d-aspartate (NMDA)-receptor antagonist MK-801 (500 pmol) or the non-NMDA-receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (50 pmol). Anatomically, most of the retrogradely labeled neurons in the ventrolateral regions and KF subnucleus of the ipsilateral PBN complex after microinjection of fast blue into the RVLM were also immunoreactive to anti-glutamate antiserum. These results suggest that a direct glutamatergic projection to the RVLM from topographically distinct regions of the PBN complex may participate in the suppression of reflex bradycardia via activation of both NMDA and non-NMDA receptors at the RVLM.
TNF-α and IL-1α induce heme oxygenase-1 via protein kinase C, Ca2+, and phospholipase A2in endothelial cells
Authors: Terry Christi M. , Clikeman Jennifer A. , Hoidal John R. , Callahan Karleen S.
Published: December 2017

Heme oxygenase-1 (HO-1), an enzyme important in protection against oxidant stress, is induced in human vascular endothelial cells by the cytokines tumor necrosis factor-α (TNF-α) and interleukin-1α (IL-1α). However, the signaling mediators that regulate the induction are not known. This study examined the involvement of protein kinase C (PKC), phospholipase A2(PLA2), calcium, and oxidants in cytokine induction of HO-1. Acute exposure to the PKC activator phorbol 12-myristate 13-acetate (PMA) stimulated HO-1 mRNA. However, prolonged exposure, which downregulates most PKC isoforms, blocked induction of HO-1 mRNA by IL-1α and TNF-α. Additionally, the phosphatase inhibitors okadaic acid and calyculin enhanced cytokine induction of HO-1. Mepacrine, a PLA2inhibitor, prevented HO-1 induction by cytokine, suggesting a role for arachidonate, the product of PLA2hydrolysis of phospholipids, in HO-1 expression. The intracellular calcium chelator 1,2-bis(2-aminophenoxy)ethane- N, N, N′, N′-tetraacetic acid acetoxymethyl ester (BAPTA-AM) blocked cytokine induction of HO-1. Paradoxically, the calcium ionophore A-23187 prevented HO-1 induction by cytokine but not by PMA. Finally, the oxidant scavenger N-acetylcysteine inhibited HO-1 induction by cytokines. These results demonstrate that TNF-α and IL-1α induction of HO-1 requires PKC-mediated phosphorylation and PLA2activation as well as oxidant generation.
Pentobarbital-sensitive EDHF comediates ACh-induced arteriolar dilation in the hamster microcirculation
Authors: de Wit Cor , Esser Norbert , Lehr Hans-Anton , Bolz Steffen-Sebastian , Pohl Ulrich
Published: December 2017

It is unclear to what extent the endothelium-derived hyperpolarizing factor (EDHF) contributes to the control of microcirculatory blood flow in vivo. We analyzed, by intravital microscopy in hamster muscles, the potential role of EDHF along the vascular tree under stimulated (ACh) or basal conditions. Experiments were performed in conscious as well as anesthetized (pentobarbital, urethan) animals. Additionally, cellular effects of the potential EDHF were studied in isolated small arteries. In pentobarbital-anesthetized animals, treatment with N ω-nitro-l-arginine (l-NNA; 30 μmol/l) and indomethacin (3 μmol/l) reduced the dilation in response to 10 μmol/l ACh from 60 ± 6 to 20 ± 4%. This nitric oxide/prostaglandin-independent dilation (NPID), which was of a similar magnitude in large and small arterioles, was abolished by potassium depolarization or charybdotoxin (ChTX, 1 μmol/l) but not by glibenclamide. In conscious animals, NPID amounted to 33 ± 3%. The inhibitor of the P-450 monooxygenase 17-octadecynoic acid (ODYA) reduced NPID further to 9 ± 4%. ChTX abolished the NPID and also reduced basal diameters (by −11 ± 3%). The induction of anesthesia with pentobarbital reduced NPID (to 12 ± 6%), whereas urethan anesthesia was without effect. Pentobarbital also reduced the ACh-induced hyperpolarization of vascular smooth muscle in isolated arteries, whereas ChTX abolished it. This study suggests that a considerable part of the ACh dilation in the microcirculation is mediated by EDHF, which also contributes to the control of basal tone in conscious animals. The direct inhibitory effect of pentobarbital and ODYA supports the idea that “microcirculatory” EDHF is a product of the cytochrome P-450 pathway. The role of EDHF might be underestimated in pentobarbital-anesthetized animals.
Regulation of NO-elicited pulmonary artery relaxation and guanylate cyclase activation by NADH oxidase and SOD
Authors: Gupte Sachin A. , Rupawalla Tasneem , Mohazzab-H. Kamal M. , Wolin Michael S.
Published: December 2017

We have previously reported that inhibition of Cu/Zn superoxide dismutase (SOD) in endothelium-removed bovine pulmonary arteries (BPA) attenuates nitrovasodilator-elicited relaxation and that a NADH oxidase linked to the redox status of cytosolic NADH is the major detectable source of superoxide ([Formula: see text]) production in this tissue. In the present study, we investigated whether NADH oxidase-derived[Formula: see text] participated in inhibition of nitrovasodilator-elicited relaxation and soluble guanylate cyclase (sGC) stimulation. Lactate (10 mM) and pyruvate (10 mM) were employed to increase and decrease, respectively, NADH-dependent[Formula: see text] production in the BPA presumably by modulating cytosolic NAD(H) through the lactate dehydrogenase reaction. A 30-min pretreatment with 10 mM diethyldithiocarbamate (DETCA) was used to inhibit Cu/Zn SOD, and S-nitroso- N-acetylpenicillamine (SNAP) was employed as a source of nitric oxide (NO). Lactate or pyruvate did not alter relaxation to NO. However, when the response to NO was inhibited by DETCA, lactate potentiated and pyruvate reduced the inhibitory effects of DETCA. SOD attenuated the inhibitory effects of DETCA plus lactate. In the presence of 10 μM SNAP, the activity of sGC in a BPA homogenate preparation (which was reconcentrated to approximate tissue conditions) was not altered by SOD. However, NADH (0.1 mM) decreased sGC activity by 70%, and this effect of NADH was attenuated in the presence of SOD. Thus cytosolic NADH redox and Cu/Zn SOD activity have important roles in controlling the inhibitory effects of [Formula: see text] derived from NADH oxidase on sGC activity and cGMP-mediated relaxation to nitrovasodilators in BPA.
Chronic activation of neurokinin-1 receptor induces pulmonary hypertension in rats
Authors: Chen Li-Wen , Chen Chau-Fong , Lai Yih-Loong
Published: December 2017

In this study we explored the hypothesis that chronic activation of neurokinin-1 (NK-1) receptor induces pulmonary hypertension in Wistar rats. First, the activation of NK-1 receptor on the pulmonary circulation was investigated by use of a chronic injection of NK-1 agonist [Ser9,Met(O2)11]-substance P (1 × 10−9mol/kg) for 2 wk at sea level (rats breathed room air) and during hypoxia (rats were placed in a hypobaric 380-Torr chamber). Second, we studied the effect of NK-1 antagonist (CP-96345) on developing and developed (after 4 wk of chronic hypoxia) pulmonary hypertension. Pulmonary arterial pressure, the weight ratio of right ventricle to left ventricle + septum, hematocrit, and substance P (SP) were measured. We found that NK-1 agonist significantly increased pulmonary arterial pressure in the sea-level but not in the hypoxic group. However, NK-1 agonist induced neither right heart hypertrophy nor polycythemia. CP-96345 significantly decreased pulmonary arterial pressure in the hypoxic group but had no effect in the sea-level group. Furthermore, CP-96345 significantly attenuated the acute SP-induced increase in pulmonary arterial pressure in the sea-level and hypoxic groups, with a larger increase in the hypoxic group. These results suggest that chronic activation of NK-1 receptor induces pulmonary hypertension and that there is an increase in the sensitivity of pulmonary vessels in response to SP in chronically hypoxic rats.
The effects of mannitol, albumin, and cardioplegia enhancers on 24-h rat heart preservation
Authors: Dunphy Gail , Richter Helen Wilkinson , Azodi Masoud , Weigand John , Sadri Fereydoon , Sellke Frank , Ely Daniel
Published: December 2017

During 24 h in vitro heart preservation and reperfusion, tissue damage occurs that seriously reduces cardiac function. Prevention of free radical production during preservation and reperfusion of ischemic tissue using free radical scavengers is of primary importance in maintaining optimal heart function in long-term preservation protocols. We examined whether mannitol (68 mM) and albumin (1.4 μM) in combination with other cardioplegia enhancers decreased free radical formation and edema and increased cardiac function during 24-h cold (5°C) heart preservation and warm (37°C) reperfusion in the Langendorff-isolated rat heart. The performance of mannitol-treated hearts was significantly decreased compared with that of hearts without mannitol treatment after 24 h of preservation with regard to recovery of diastolic pressure, contractility (+dP/d t), relaxation (−dP/d t), myocardial creatine kinase release, coronary flow, and lipid peroxidation. Albumin-treated hearts demonstrated higher cardiac function (contractility and coronary flow especially) than hearts not treated with albumin or hearts treated with mannitol, and this appears to be due to the positive effects of increased cellular metabolism and the enhancement of membrane stability.
Regional contributions ofKv1.4,Kv4.2, andKv4.3to transient outward K+current in rat ventricle
Authors: Wickenden A. D. , Jegla T. J. , Kaprielian R. , Backx P. H.
Published: December 2017

The aim of the present study was to assess differences in transient outward potassium current ( Ito) between the right ventricular free wall and the interventricular septum of the adult rat ventricle and to evaluate the relative contributions of Kv4.2, Kv4.3, and Kv1.4 to Itoin these regions. The results show that Itois composed of both rapidly and slowly recovering components in the right wall and septum. The fast component had a significantly higher density in the right free wall than in the septum, whereas the slow component did not differ between the two sites. Kv4.2mRNA and protein levels were also highest in the right wall and correlated with Itodensity, whereas Kv4.3 was expressed uniformly in these regions. The kinetics of the rapidly recovering component of Itoin myocytes was similar to that recorded in tsa-201 cells expressing Kv4.2 and Kv4.3 channels. Kv1.4 mRNA and protein expression correlated well with the density of the slowly recovering Ito, whereas the recovery kinetics of the slow component were identical to Kv1.4 expressed in tsa-201 cells. In conclusion, expression of Kv1.4, Kv4.2, and Kv4.3 differs between regions in rat hearts. Regionally specific differences in the genetic composition of Itocan account for the region-specific properties of this current.
Effects of aminopeptidase P inhibition on kinin-mediated vasodepressor responses
Authors: Kitamura Shin-Ichi , Carbini Luis A. , Simmons William H. , Scicli A. Guillermo
Published: December 2017

We studied in anesthetized rats whether aminopeptidase P (AMP) may be involved in bradykinin (BK) metabolism and responses. For this we inhibited AMP with the specific inhibitor apstatin (Aps). Studies were done with Aps alone or together with the angiotensin-converting enzyme inhibitor lisinopril (Lis). Aps increased the vasodepressor response to an intravenous bolus of BK (400 ng/kg): vehicle, −3.0 ± 0.7 mmHg; Aps, −7.8 ± 0.7 mmHg ( P < 0.01 vs. vehicle); Lis, −23.8 ± 1.8 mmHg; Aps + Lis, −37.5 ± 1.9 mmHg ( P < 0.01 vs. Lis). Aps did not affect the vasodepressor response to BK given into the descending aorta. Plasma BK increased only in Aps + Lis-treated rats (in pg/ml): control, 48.0 ± 1.4; Lis, 57.5 ± 7.6; Aps + Lis, 121.8 ± 30.6 ( P < 0.05 vs. control or Lis), whereas in rats infused with BK (400 ng ⋅ kg−1 ⋅ min−1for 5 min), Aps increased plasma BK (in pg/ml): control, 51.9 ± 2.5; Aps, 83.5 ± 20.5; Lis, 725 ± 225; Aps + Lis, 1,668 ± 318 ( P < 0.05, Aps vs. control and Lis vs. Aps + Lis). In rats with aortic coarctation hypertension, the acute antihypertensive effects of Aps plus Lis were greater than Lis alone ( P < 0.01). Hoe-140, a BK B2-receptor antagonist, abolished the difference. We concluded that in the rat AMP contributes to regulation of BK metabolism and responses.
Bradykinin metabolism in the postinfarcted rat heart: role of ACE and neutral endopeptidase 24.11
Authors: Raut Robert , Rouleau Jean-Lucien , Blais Charles , Gosselin Hugues , Molinaro Giuseppe , Sirois Martin G. , Lepage Yves , Crine Philippe , Adam Albert
Published: December 2017

The respective role of angiotensin-converting enzyme (ACE) and neutral endopeptidase 24.11 (NEP) in the degradation of bradykinin (BK) has been studied in the infarcted and hypertrophied rat heart. Myocardial infarction (MI) was induced in rats by left descendant coronary artery ligature. Animals were killed, and hearts were sampled 1, 4, and 35 days post-MI. BK metabolism was assessed by incubating synthetic BK with heart membranes from sham hearts and infarcted (scar) and noninfarcted regions of infarcted hearts. The half-life ( t ½) of BK showed significant differences among the three types of tissue at 4 days [sham heart (114 ± 7 s) > noninfarcted region (85 ± 4 s) > infarcted region (28 ± 2 s)] and 35 days post-MI [sham heart (143 ± 6 s) = noninfarcted region (137 ± 9 s) > infarcted region (55 ± 4 s)]. No difference was observed at 1 day post-MI. The participation of ACE and NEP in the metabolism of BK was defined by preincubation of the membrane preparations with enalaprilat, an ACE inhibitor, and omapatrilat, a vasopeptidase inhibitor that acts by combined inhibition of NEP and ACE. Enalaprilat significantly prevented the rapid degradation of BK in every tissue type and at every sampling time. Moreover, omapatrilat significantly increased the t ½ of BK compared with enalaprilat in every tissue type and at every sampling time. These results demonstrate that experimental MI followed by left ventricular dysfunction significantly modifies the metabolism of exogenous BK by heart membranes. ACE and NEP participate in the degradation of BK since both enalaprilat and omapatrilat have potentiating effects on the t ½ of BK.
Active renin and angiotensinogen in cardiac interstitial fluid after myocardial infarction
Authors: Hirsch Alan T. , Opsahl John A. , Lunzer Mary M. , Katz Stephen A.
Published: December 2017

The renin-angiotensin system promotes cardiac hypertrophy after myocardial infarction. The purpose of this study was to measure renin and angiotensinogen in plasma and myocardium 10 days after myocardial infarction. Infarction involving 45 ± 4% of left ventricular circumference with accompanying hypertrophy was induced in rats ( n = 14). Plasma and myocardial renin were increased after infarction compared with sham controls ( n = 8) (27.4 ± 3.2 vs. 7.5 ± 1.8 ng ANG I ⋅ ml plasma ⋅ h−1, P < 0.0002; and 8.8 ± 1.6 vs. 2.5 ± 0.1 ng ANG I ⋅ g myocardium−1⋅ h−1, P < 0.008, respectively). After infarction, myocardial renin was correlated with infarct size ( r = 0.62, P < 0.02) and plasma renin ( r = 0.55, P < 0.04). Plasma angiotensinogen decreased in infarct animals, but myocardial angiotensinogen was not different from shams (1.1 ± 0.08 vs. 2.03 ± 0.06 nM/ml plasma, P < 0.002; and 0.081 ± 0.008 vs. 0.070 ± 0.004 nM/g myocardium, respectively). In conclusion, myocardial renin increased after infarction in proportion to plasma renin and infarct size, and myocardial angiotensinogen was maintained after infarction despite decreased plasma angiotensinogen and increased levels of myocardial renin.
Molecular β-adrenergic signaling abnormalities in failing rabbit hearts after infarction
Authors: Maurice John P. , Shah Ashish S. , Kypson Alan P. , Hata Jonathan A. , White David C. , Glower Donald D. , Koch Walter J.
Published: December 2017

We studied alterations in the β-adrenergic receptor (β-AR) system of rabbit hearts during the development of heart failure (HF) after myocardial infarction (MI) to determine whether the molecular β-AR abnormalities associated with human HF exist in this animal model. Rabbit HF was established 3 wk after left circumflex coronary artery (LCX) ligation by in vivo physiological measurements, and molecular β-AR signaling was examined in tissue and cultured ventricular myocytes. We found that there was a significant global reduction in β-AR density by ∼50% in both ventricles of MI animals compared with sham-operated control animals and that functional β-AR coupling was significantly reduced. Importantly, as found in human HF, myocardial protein levels and activity of the β-AR kinase (β-ARK1) and Gαiwere found to be significantly elevated in MI rabbits, suggesting that these molecules are contributing to myocardial dysfunction. Thus the myocardial β-AR system of this rabbit model of HF shares important biochemical characteristics with human HF and therefore is an ideal laboratory model to investigate novel therapeutic targets for the treatment of HF.
Further evidence for the selective disruption of intercellular communication by heptanol
Authors: Christ G. J. , Spektor M. , Brink P. R. , Barr L.
Published: December 2017

The lack of selective gap junctional uncoupling agents has hampered evaluation of the contribution of intercellular communication to pharmacomechanical coupling and vascular contractility. Thus we further explored the utility and selectivity of heptanol as a gap junctional uncoupling agent in isolated rat aortic rings. Fifty-two aortic rings were obtained from 15 rats and were precontracted to ∼75% of maximum with phenylephrine (PE). When contraction achieved steady state (∼5 min), a single concentration of heptanol (200 μM) was added to each aortic ring at 1- to 3-min intervals for up to 42 min post-PE addition. At early time points (5–10 min after PE), heptanol elicited an ∼50% loss of tension (i.e., relaxation). At subsequent time points post-PE, a gradual and time-dependent decrease in the magnitude of the heptanol-induced relaxation was observed until, after ∼40 min, addition of heptanol was associated with little, if any, detectable relaxation. Linear regression analysis of the magnitude of the heptanol-induced relaxation vs. the square root of the elapsed time interval (from addition of PE) revealed a highly significant negative correlation ( P < 0.001, R = 0.81). Studies conducted on KCl-precontracted aortic rings revealed no detectable heptanol-induced relaxation after development of the steady-state KCl-induced contraction. These data extend our previous observations to further document the potential utility of heptanol as a “relatively selective” uncoupling agent.
Leukocyte-endothelial cell interactions in nitric oxide synthase-deficient mice
Authors: Lefer David J. , Jones Steven P. , Girod Wesley G. , Baines Amarpreet , Grisham Matthew B. , Cockrell Adam S. , Huang Paul L. , Scalia Rosario
Published: December 2017

Nitric oxide (NO) is known to be an important endogenous modulator of leukocyte-endothelial cell interactions within the microcirculation. We examined leukocyte rolling and adhesion under baseline conditions and following thrombin (0.25 U/ml) superfusion in the mesentery of wild-type, inducible NOS (iNOS)-deficient (−/−), neuronal NOS (nNOS) −/−, and endothelial cell NOS (ecNOS) −/− mice to further our understanding of NO and leukocyte function. Baseline leukocyte rolling (cells/min) was significantly elevated in both the nNOS −/− (30.0 ± 4.0) and ecNOS −/− mice (67.0 ± 12.0) compared with wild-type mice (11.0 ± 1.4). In addition, baseline leukocyte adherence (cells/100 μm of vessel) was also significantly elevated in the nNOS −/− (5.2 ± 1.0) and ecNOS −/− (13.0 ± 1.3) compared with wild-type animals (1.3 ± 0.5). Deficiency of iNOS had no effect on baseline leukocyte rolling or adhesion in the mesentery. Baseline surface expression of P-selectin was observed in 68.0 ± 9.0% of intestinal venules in ecNOS −/− mice compared with 10.0 ± 2.0% in wild-type mice. Additional studies demonstrated that administration of an anti-P-selectin monoclonal antibody (RB40.34) or the soluble P-selectin ligand, PSGL-1, completely inhibited the increased rolling and firm adhesion response in nNOS −/− and ecNOS −/− mice. Transmigration of neutrophils into the peritoneum following thioglycollate injection was also significantly augmented in nNOS −/− and ecNOS −/− mice. These studies clearly indicate the NO derived from both nNOS and ecNOS is critical in the regulation of leukocyte-endothelial cell interactions.