bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional heterogeneity of endothelial P2 purinoceptors in the cerebrovascular tree of the rat
Authors: You Junping , Johnson T. David , Marrelli Sean P. , Bryan Robert M.
Published: December 2017

The effects of stimulating P2Y1 or P2Y2 purinoceptors on the endothelium of isolated middle cerebral arteries (MCAs), third-order branches of the MCA (bMCAs), and penetrating arterioles (PAs) of the rat were studied. After pressurization and development of spontaneous tone (25% contraction), resting diameters for MCAs, bMCAs, and PAs were 203 ± 5 ( n = 50), 99 ± 2 ( n = 42), and 87 ± 2 μm ( n = 53), respectively. Luminal application of the P2Y1-selective agonist 2-methylthioadenosine 5′-triphosphate elicited dose-dependent dilations (or loss of intrinsic tone) in MCAs but not in bMCAs or PAs. The dilation in MCAs was completely blocked by removal of the endothelium or by nitro-l-arginine methyl ester (10−5 M), an inhibitor of NO synthase. Luminal application of the P2Y2-selective agonist ATP elicited dilations in MCAs, bMCAs, and PAs. Removal of the endothelium abolished the dilations in all vessel groups. Dilations in MCAs have been shown to involve both NO and endothelium-derived hyperpolarizing factor (EDHF). The dilations in bMCAs and PAs had a minor NO component and prominent EDHF component; that is, 1) the dilations to ATP were not diminished by the combined inhibition of NO synthase and cyclooxygenase, 2) the dilations were accompanied by significant hyperpolarizations of the vascular smooth muscle (∼15 mV), and 3) the dilations were completely abolished by the calcium-activated potassium channel blocker charybdotoxin. We concluded that the role of NO in purinoceptor-induced dilations diminishes along the cerebrovascular tree in the rat, whereas the role of EDHF becomes more prominent.
Promotion of copper excretion from the isolated rat heart attenuates postischemic cardiac oxidative injury
Authors: Powell Saul R. , Gurzenda Ellen M. , Wingertzahn Mark A. , Wapnir Raul A.
Published: December 2017

This study examined the role of Cu as a mediator of cardiac postischemic oxidative injury. Isolated rat hearts were subjected to 20 min of normothermic global ischemia, followed by 30 min of reperfusion; after 20 min of preischemic loading with Krebs-Henseleit buffer ± 20 or 30 μM zinc-bis-histidinate (Zn-His2), 0.5 mM deferoxamine (DEF) or 42 μM neocuproine (NEO). Postischemic developed systolic pressure and rate-pressure product were highest and postischemic end-diastolic pressure was lowest in hearts treated with 20 or 30 μM Zn-His2 and 0.5 mM DEF. Cu efflux was significantly increased by 225 and 290% (end of preischemic loading), and 325 and 375% (immediate postischemic period) of control basal rates in hearts treated with 30 μM Zn-His2 and 0.5 mM DEF, respectively. NEO did not effect any of these parameters. By the end of ischemia, protein carbonyls were lowest in Zn-His2-treated hearts and highest in DEF-treated hearts when compared with control hearts. The results of this study suggest that removal of redox-active Cu before ischemia has beneficial effects, indicating a mediatory role in postischemic cardiac oxidative injury.
Relation between activation sequence fluctuation and arrhythmogenicity in sodium-channel blockades
Authors: Watanabe Tetsu , Yamaki Michiyasu , Kubota Isao , Tachibana Hidetada , Tomoike Hitonobu
Published: December 2017

To examine the correlation between activation sequence fluctuation and arrhythmogenicity, we investigated temporal changes in the activation sequence by measuring activation times [negative first derivative of voltage over time (−d V/d t) in QRS] from the entire heart in 18 dogs. The heart was paced by constant atrial stimulation. The character of the activation sequence fluctuation was established by a principal component analysis, in which the first principal component was defined as a stable component of the sequence and the second or third component as a fluctuated component. Steady state contained 2.2 ± 0.6% (percent total principal component, mean ± SD) of fluctuated components, which appeared in a beat-by-beat manner (activation sequence alternans). Activation sequence alternans was observed only during flecainide administration and not during lidocaine or disopyramide administration. Fluctuated components at a high dose of flecainide significantly increased (3.3 ± 0.8%). Ventricular fibrillation ensued in all dogs ( n = 6) exposed to flecainide after an increase in activation sequence alternans. In conclusion, flecainide evoked local activation sequence alternans. This phenomenon correlated with the occurrence of ventricular fibrillation.
Inhibition of guanylate cyclase stimulation by NO and bovine arterial relaxation to peroxynitrite and H2O2
Authors: Iesaki Takafumi , Gupte Sachin A. , Kaminski Pawel M. , Wolin Michael S.
Published: December 2017

The inhibitor of soluble guanylate cyclase (sGC) stimulation by nitric oxide (NO), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), was examined for its effects on the prolonged relaxation of endothelium-removed bovine coronary (BCA) and pulmonary (BPA) arteries to peroxynitrite (ONOO−) and on H2O2-elicited relaxation and sGC stimulation. Our previous studies suggest that ONOO−causes a prolonged relaxation of BPA by regenerating NO and that a 2-min exposure of BCA or BPA to 50 nM NO causes an ONOO−-elicited relaxation. The relaxation of K+-precontracted BCA to 50 nM NO or 100 μM ONOO−was essentially eliminated by 10 μM ODQ. ODQ also eliminated relaxation to 0.1 nM-10 μM of NO donor S-nitroso- N-acetyl-penicillamine (SNAP), but it did not alter relaxation to 1–300 μM H2O2. Similar responses were also observed in BPA. ODQ did not increase lucigenin-detectable superoxide production in BCA, and it did not alter luminol-detectable endogenous ONOO−formation observed during a 2-min exposure of BCA to 50 nM NO. In addition, ODQ did not affect tissue release of NO after 2 min exposure of BCA to 50 nM NO. The activity of sGC in BPA homogenate that is stimulated by endogenous H2O2was not altered by ODQ, whereas sGC activity in the presence of 10 μM SNAP (+fungal catalase) was reduced by ODQ. Thus relaxation of K+-precontracted BCA and BPA to ONOO−appears to be completely mediated by NO stimulation of sGC, whereas the actions of ODQ suggest that NO is not involved in H2O2-elicited relaxation and sGC stimulation. This study did not detect evidence for the participation of additional mechanisms potentially activated by ONOO−in the responses studied.
Two types of action potential configuration in single cardiac Purkinje cells of sheep
Authors: Verkerk Arie O. , Veldkamp Marieke W. , Abbate Fabio , Antoons Gudrun , Bouman Lennart N. , Ravesloot Jan H. , van Ginneken Antoni C. G.
Published: December 2017

Membrane potentials and currents of isolated sheep Purkinje and ventricular cells were compared using patch-clamp and microelectrode techniques. In ∼50% of Purkinje cells, we observed action potentials that showed a prominent phase 1 repolarization and relatively negative plateau (LP cells). Action potential configuration of the remaining Purkinje cells was characterized by little phase 1 repolarization and relatively positive plateau (HP cells). Microelectrode impalement of Purkinje strands also revealed these two types of action potential configuration. In LP cells, the density of L-type Ca2+ current ( I Ca,L) was lower, whereas the density of transient outward K+ current was higher, than in HP cells. Action potentials of HP cells strongly resembled those of ventricular cells. Densities of inward rectifier current and I Ca,L were significantly higher in ventricular cells compared with densities in both LP and HP Purkinje cells. Differences in current densities explain the striking differences in action potential configuration and the stimulus frequency dependency thereof that we observed in LP, HP, and ventricular cells. We conclude that LP Purkinje cells, HP Purkinje cells, and ventricular cells of sheep each have a unique action potential configuration.
Hypoxia stimulates proliferation and interleukin-1α production in human vascular smooth muscle cells
Authors: Cooper Angela L. , Beasley Debbie
Published: December 2017

Several lines of evidence indicate that hypoxia is a stimulus to vascular smooth muscle cell (VSMC) proliferation that occurs in pulmonary hypertension. The present study tested the hypothesis that low O2tension directly stimulates human VSMC proliferation by inducing them to produce interleukin (IL)-1, a potent autocrine growth factor for human VSMC. Human VSMC derived from pulmonary artery, aorta, or saphenous vein were incubated in either a normal in vitro O2environment (20% O2) or in chambers containing low (∼1%) or moderate (5%) O2. Levels of IL-1α and IL-1β mRNA increased in human VSMC after 24–48 h of incubation in low O2compared with levels in normoxic cells and then decreased upon subsequent reoxygenation. Levels of cell-associated IL-1α also increased progressively after 24–48 h in low O2; however, detectable IL-1α was not released from the cells in the media. IL-1β was detectable in cell lysates and supernatants; however, the levels were not affected by exposure to low O2. mRNA encoding for tumor necrosis factor-α (TNF-α), a related cytokine and VSMC mitogen, was not detectable in human VSMC exposed to either low or 20% O2. Proliferation of human VSMC was not stimulated during exposure to low O2, despite the fact that cells remained responsive to the mitogenic effect of exogenous IL-1. Interestingly, however, exposure to 5% O2enhanced proliferation of human VSMC but did not induce IL-1α production. Inhibition of IL-1 binding to the type I IL-1 receptor by exogenous addition of IL-1-receptor antagonist (10 μg/ml) did not attenuate the proliferation rates of human VSMC incubated in 20%, 5%, or low O2or in human VSMC that were reoxygenated after exposure to low O2. These results demonstrate two direct and distinct effects of hypoxia on VSMC. Exposure to moderately low O2tension induces VSMC proliferation, independent of IL-1, whereas exposure to very low O2tension induces production of IL-1α.
EP receptor-mediated inhibition by prostaglandin E1of cardiac L-type Ca2+current of rabbits
Authors: Yamamoto Taku , Habuchi Yoshizumi , Tanaka Hideo , Suto Fumiaki , Morikawa Junichiro , Kashima Kei , Yoshimura Manabu
Published: December 2017

Prostaglandin E1(PGE1) has cardioprotective effects on the ischemic-reperfused heart. To clarify the mechanisms underlying the protective action of PGE1on myocardium, we examined the effect of PGE1on the L-type Ca2+current ( ICa) using single atrial cells from rabbits. PGE1did not show a significant effect on basal ICabut inhibited the ICaprestimulated by isoproterenol (Iso, 30 nM). This inhibition was concentration dependent (EC50= 0.027 μM). Both sulprostone, a specific PGE receptor subtype (EP1and EP3) agonist, and 11-deoxy-PGE1, an EP3agonist, inhibited the Iso-stimulated ICa, similar to PGE1. Pretreatment with pertussis toxin (PTX) abolished the PGE1inhibition of ICa. Both the application of forskolin plus IBMX and intracellular dialysis with 8-bromoadenosine 3′,5′-cyclic monophosphate eliminated the effect of PGE1. PGE1did not show any further inhibition of ICawhen the effect of Iso was almost fully antagonized by acetylcholine. Methylene blue (guanylate cyclase inhibitor), KT-5823 (cGMP-dependent protein kinase inhibitor), and erythro-9-(2-hydroxy-3-nonyl)adenine (type II phosphodiesterase inhibitor) did not significantly change the inhibitory effect of PGE1. These findings suggest that 1) PGE1inhibits Iso-stimulated ICaby binding to the EP3receptor and 2) the PTX-sensitive and cAMP-dependent pathway is involved in the PGE1inhibition of ICa, but the nitric oxide-cGMP-dependent pathway is not. The PGE1-induced antiadrenergic effect shown in this study may contribute to the PGE1protection of myocardium against ischemia.
Determinants of mechanical properties in the developing ovine thoracic aorta
Authors: Wells Sarah M. , Langille B. Lowell , Lee J. Michael , Adamson S. Lee
Published: December 2017

We previously reported changes in mechanical properties and collagen cross-linking of the ovine thoracic aorta during perinatal development and postnatal maturation, and we now report changes in biochemical composition (elastin, collagen, and DNA contents per mg wet wt) over the same developmental intervals. A comparison of results from the present and previous studies has yielded novel and important observations concerning the relationship between aortic mechanics and composition during maturation. Developmental changes in aortic incremental elastic modulus at low tensile stress ( E low) closely followed changes in relative elastin content (i.e., per mg wet wt). An 89% increase in E low during the perinatal period was associated with a 69% increase in relative elastin content, whereas neither variable changed during postnatal life. Incremental elastic modulus at high tensile stress ( E high) did not change during the perinatal period but increased 88% during postnatal life. This pattern closely paralleled changes in collagen cross-linking index, which did not change perinatally but almost doubled postnatally. In contrast, relative collagen content (per mg wet wt) increased only slightly from fetal to adult life, a trend that was unrelated to aortic mechanics. Substantial, progressive decreases in measures of wall viscosity (pressure wave attenuation coefficient and viscoelastic phase angle) from fetal to adult life followed the pattern observed for relative DNA (smooth muscle cell) content (per mg wet wt). Our findings suggest that accumulation of elastin per milligram wet weight contributes most to developmental changes in E low, change in collagen cross-linking is the primary determinant of developmental changes in E high, and cell accumulation contributes most to developmental changes in wall viscosity.
Regional alterations in SR Ca2+-ATPase, phospholamban, and HSP-70 expression in chronic hibernating myocardium
Authors: Fallavollita James A. , Jacob Saji , Young Rebeccah F. , Canty John M.
Published: December 2017

We sought to identify mechanisms for chronic dysfunction in hibernating myocardium. Pigs were instrumented with a left anterior descending artery stenosis for 3 mo. Angiography demonstrated high-grade stenoses and hibernating myocardium with 1) severe anterior hypokinesis ( P < 0.001 vs. shams), 2) reduced subendocardial perfusion [0.73 ± 0.05 (SE) vs. 1.01 ± 0.06 ml ⋅ min−1⋅ g−1in normal, P < 0.001], and 3) critically reduced adenosine flow (1.0 ± 0.17 vs. 3.84 ± 0.26 ml ⋅ min−1⋅ g−1in normal, P < 0.001). Histology did not reveal necrosis. Northern blot analysis of hibernating myocardium demonstrated regional downregulation in mRNAs for sarcoplasmic reticulum (SR) proteins phospholamban (0.76 ± 0.08 vs. 1.07 ± 0.06, P < 0.02) and SR Ca2+-ATPase (0.83 ± 0.06 vs. 1.02 ± 0.06, P < 0.05) with no change in calsequestrin (1.08 ± 0.06 vs. 0.96 ± 0.05, P = not significant). Heat shock protein (HSP)-70 mRNA was regionally induced in hibernating myocardium (2.4 ± 0.3 vs. 1.0 ± 0.11, P < 0.01). Directionally similar changes were confirmed by Western blot analysis of respective proteins. Our results indicate that hibernating myocardium exhibits a molecular phenotype that on a regional basis is similar to end-stage ischemic cardiomyopathy. This supports the hypothesis that SR dysfunction from reversible ischemia may be an early defect in the progression of left ventricular dysfunction.
Acute hyperglycemia depresses arteriolar NO formation in skeletal muscle
Authors: Lash J. M. , Nase G. P. , Bohlen H. G.
Published: December 2017

In the rat intestinal and cerebral microvasculatures, acute d-glucose hyperglycemia suppresses endothelium-dependent dilation to ACh without affecting endothelium-independent dilation to nitroprusside. This study determined whether acute hyperglycemia suppressed arteriolar wall nitric oxide concentration ([NO]) at rest or during ACh stimulation and inhibited nitroprusside-, ACh- or contraction-induced dilation of rat spinotrapezius arterioles. Vascular responses were measured before and after 1 h of topical 300 mg/100 mld-glucose; arteriolar [NO] was measured with NO-sensitive microelectrodes. Arteriolar dilation to ACh was not significantly altered after superfusion of 300 mg/100 mld-glucose. However, after hyperglycemia, arteriolar [NO] was not increased by ACh, compared with a 300 nM increase attained during normoglycemia. Arteriolar dilation to submaximal nitroprusside and muscle contractions was enhanced by hyperglycemia. These results indicated that in the rat spinotrapezius muscle, acute hyperglycemia suppressed arteriolar NO production while simultaneously augmenting vascular smooth muscle responsiveness to nitroprusside, presumably through cGMP-mediated mechanisms. In effect, this may have allowed ACh- and muscle contraction-induced vasodilation to be maintained during hyperglycemia despite an impaired NO system.
Catecholamine handling in the porcine heart: a microdialysis approach
Authors: Lameris T. W. , van den Meiracker A. H. , Boomsma F. , Alberts G. , de Zeeuw S. , Duncker D. J. , Verdouw P. D. , Veld A. J. Man In ’t
Published: December 2017

Experimental findings suggest a pronounced concentration gradient of norepinephrine (NE) between the intravascular and interstitial compartments of the heart, compatible with an active neuronal reuptake (U1) and/or an endothelial barrier. Using the microdialysis technique in eight anesthetized pigs, we investigated this NE gradient, both under baseline conditions and during increments in either systemic or myocardial interstitial fluid (MIF) NE concentration. At steady state, baseline MIF NE (0.9 ± 0.1 nmol/l) was higher than arterial NE (0.3 ± 0.1 nmol/l) but was not different from coronary venous NE (1.5 ± 0.3 nmol/l). Local U1 inhibition raised MIF NE concentration to 6.5 ± 0.9 nmol/l. During intravenous NE infusions (0.6 and 1.8 nmol ⋅ kg−1⋅ min−1), the fractional removal of NE by the myocardium was 79 ± 4% to 69 ± 3%, depending on the infusion rate. Despite this extensive removal, the quotient of changes in MIF and arterial concentration (ΔMIF/ΔA ratio) for NE were only 0.10 ± 0.02 for the lower infusion rate and 0.11 ± 0.01 for the higher infusion rate, whereas U1 blockade caused the ΔMIF/ΔA ratio to rise to 0.21 ± 0.03 and 0.36 ± 0.05, respectively. From the differences in ΔMIF/ΔA ratios with and without U1 inhibition, we calculated that 67 ± 5% of MIF NE is removed by U1. Intracoronary infusion of tyramine (154 nmol ⋅ kg−1⋅ min−1) caused a 15-fold increase in MIF NE concentration. This pronounced increase was paralleled by a comparable increase of NE in the coronary vein. We conclude that U1 and extraneuronal uptake, and not an endothelial barrier, are the principal mechanisms underlying the concentration gradient of NE between the interstitial and intravascular compartments in the porcine heart.
TNF-α enhances cardiac myocyte NO production through MAP kinase-mediated NF-κB activation
Authors: Kan Hong , Xie Zirong , Finkel Mitchell S.
Published: December 2017

We have previously reported that interleukin-1β (IL-1β) alone induced nitric oxide (NO) production by neonatal rat cardiac myocytes (CM). The effects of tumor necrosis factor-α (TNF-α) on inducible NO synthase (iNOS) were not characterized. Unlike IL-1β, TNF-α alone failed to enhance NO production in CM. However, the addition of TNF-α to IL-1β significantly enhanced iNOS mRNA expression, iNOS protein synthesis, and NO production ([Formula: see text]). TNF-α enhancement of IL-1β-induced[Formula: see text] production was blocked by PD-98059, a selective mitogen-activated protein (MAP) kinase kinase inhibitor, but not calphostin C (Cal C), a protein kinase C inhibitor. TNF-α-enhanced MAP kinase activity was associated with an increase in IL-1β-stimulated NF-κB activity. PD-98059, but not Cal C, inhibited both TNF-α-enhanced MAP kinase and NF-κB activities. Thus TNF-α enhancement of IL-1β-induced NO production is associated with MAP kinase-mediated activation of NF-κB.
Characterization of MAP kinase and PKC isoform and effect of ACE inhibition in hypertrophy in vivo
Authors: Kim L. , Lee T. , Fu J. , Ritchie M. E.
Published: December 2017

Protein kinase C (PKC) and mitogen-activated protein (MAP) kinase activation appear important in conferring hypertrophy in vitro. However, the response of PKC and MAP kinase to stimuli known to induce hypertrophy in vivo has not been determined. We recently demonstrated that pressure-overload hypertrophy induced a transiently transfected gene driven by an hypertrophy responsive enhancer (HRE) through a marked increase in binding activity of its interacting nuclear factor (HRF). These data suggested that the HRE/HRF could serve as a target for evaluating the signal transduction events responsible for hypertrophy in vivo. Accordingly, we characterized MAP kinase and PKC isoform activation, injected HRE driven reporter gene expression, and HRF binding activity in rat hearts subjected to ascending aortic clipping or sham operation in the presence of the angiotensin-converting enzyme (ACE) inhibitor fosinopril, hydralazine, or no treatment. Analyses showed that PKC-ε and MAP kinase were acutely activated following ascending aortic ligature and that fosinopril significantly inhibited but did not completely abrogate PKC-ε and MAP kinase activation. However, fosinopril completely prevented pressure overload-mediated induction of HRE containing constructs and obviated increased HRF binding activity. These results suggest a direct relationship between ACE activity and HRE/HRF-mediated gene activation and imply that PKC-ε and MAP kinase may be involved in transducing this signal.
Endothelin-1 causes P-selectin-dependent leukocyte rolling and adhesion within rat mesenteric microvessels
Authors: Sanz Maria-Jesus , Johnston Brent , Issekutz Andrew , Kubes Paul
Published: December 2017

Endothelin-1 (ET-1) is a potent vasoconstrictor postulated to play a role in hypertension, ischemia-reperfusion, and atherosclerosis. In addition to these contributions, it has been also proposed to induce leukocyte-endothelial cell interactions. The aim of the present study was to assess the mechanisms of action of ET-1 on leukocyte recruitment in vivo. Intravital microscopy of the rat mesenteric postcapillary venules was used. Ten minutes after 1 nM ET-1 superfusion, a significant increase in leukocyte rolling (77.5 ± 22.6 vs. 20.5 ± 4.5 cells/min) and adhesion (15.5 ± 2.9 vs. 3.0 ± 0.8 cells/100 μm) but not emigration was observed. These effects were found not to be mediated by mast cell activation. No platelet-endothelial cell interactions were detected in this in vivo system and furthermore, flow cytometry analysis revealed no increase of P-selectin expression in rat platelets on ET-1 stimulation. Pretreatment of animals with an anti-rat P-selectin monoclonal antibody (mAb) dramatically reduced leukocyte rolling and adhesion by 100 and 94% respectively when compared with control mAb-treated animals. At this dose of ET-1, a very transient decrease in shear rate was detected, arteriolar diameter was significantly reduced but venular diameter remained unchanged. A similar mechanical reduction in blood flow did not induce leukocyte recruitment. Thus this study demonstrates that ET-1 can directly cause significant leukocyte rolling and adhesion adding to its potential pathophysiological role in the development of disease states of the cardiovascular system.
Critical P O 2 of skeletal muscle in vivo
Authors: Richmond Keith N. , Shonat Ross D. , Lynch Ronald M. , Johnson Paul C.
Published: December 2017

The main purpose of this study was to determine the interstitial oxygen tension at which aerobic metabolism becomes limited (critical [Formula: see text]) in vivo in resting skeletal muscle. Using an intravital microscope system, we determined the interstitial oxygen tension at 20-μm-diameter tissue sites in rat spinotrapezius muscle from the phosphorescence lifetime decay of a metalloporphyrin probe during a 1-min stoppage of muscle blood flow. In paired experiments NADH fluorescence was measured at the same sites during flow stoppage. NADH fluorescence rose significantly above control when interstitial[Formula: see text] fell to 2.9 ± 0.5 mmHg ( n = 13) and was not significantly different (2.4 ± 0.5 mmHg) when the two variables were first averaged for all sites and then compared. Similar values were obtained using the abrupt change in rate of[Formula: see text] decline as the criterion for critical [Formula: see text]. With a similar protocol, we determined that NADH rose significantly at a tissue site centered 30 μm from a collecting venule when intravascular[Formula: see text] fell to 7.2 ± 1.5 mmHg. The values for critical interstitial and critical intravascular[Formula: see text] are well below those reported during free blood flow in this and in other muscle preparations, suggesting that oxygen delivery is regulated at levels well above the minimum required for oxidative metabolism. The extracellular critical[Formula: see text] found in this study is slightly greater than previously found in vitro, possibly due to differing local conditions rather than a difference in metabolic set point for the mitochondria.
Effect of tumor necrosis factor-α, IL-1β, and IL-6 on interstitial fluid pressure in rat skin
Authors: Nedrebø Torbjørn , Berg Ansgar , Reed Rolf K.
Published: December 2017

Interstitial fluid pressure (Pif) decreases in several experimental models of acute inflammation, enhancing edema formation. The present study was designed to determine the effect of tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and IL-1β as well as lipopolysaccharides (LPS) on Pifin a model of gram-negative sepsis. Pifwas measured in the paw skin of anesthetized rats (pentobarbital sodium, 50 mg/kg ip) using micropipettes (3–7 μm) and servo-controlled counterpressure technique. Test substances were injected intra-arterially (ia), intravenously (iv), or subdermally (sd). After intra-arterial or intravenous administration, the test substances were circulated for 1 min before circulatory arrest was induced with an intravenous injection of KCl while the rats were under pentobarbital anesthesia. Circulatory arrest was induced to avoid edema formation, which would raise interstitial fluid volume to cause a more positive Pif. Administration of 0.5 ml of LPS (5 mg/ml ia) lowered Pifsignificantly from control values of −0.2 ± 0.3 to −2.0 ± 0.3 mmHg ( P < 0.05) within 1 h. Corresponding values for TNF-α (500 ng/ml iv) were −0.4 ± 0.2 to −2.3 ± 0.1 mmHg ( P < 0.05). Administration of 5 μl (5 mg/ml sd) of LPS did not affect Pifsignificantly ( P > 0.05), but TNF-α, IL-1β, and IL-6 had a significant effect on Pifwhen given subdermally. IL-6 (50 ng/ml) caused a decrease in Piffrom control values of −1.2 ± 0.3 to −2.8 ± 0.5 mmHg ( P < 0.05) within 1 h. The experiments demonstrate that LPS, TNF-α, IL-1β, and IL-6 induce lowering of Pifwhen given intravenously or intra-arterially, whereas only TNF-α, IL-1β, and IL-6 induce lowering of Pifwhen given subdermally. We therefore suggest that the lowering of Pifin this experimental model of sepsis is related to the release of and a local effect in skin of TNF-α, IL-1β, and IL-6.
Hemodynamic effects of unloading the old heart
Authors: Nussbacher Amit , Gerstenblith Gary , O'connor Frances C. , Becker Lewis C. , Kass David A. , Schulman Steven P. , Fleg Jerome L. , Lakatta Edward G.
Published: December 2017

A reduction in upright exercise capacity with aging in healthy individuals is accompanied by acute left ventricular (LV) dilatation and impaired LV ejection. To determine whether acute vasodilator administration would improve LV ejection during exercise, sodium nitroprusside (NP) was administered to 16 healthy subjects, ages 64–84 yr, who had been screened for the absence of coronary heart disease by prior exercise thallium scintigraphy. Infusion of NP (0.3–1.0 μg ⋅ kg−1 ⋅ min−1), titrated to reduce the resting mean arterial pressure 10% (and eliminate the late augmentation of carotid arterial pressure), increased LV ejection fraction (EF) compared with placebo during upright, maximal graded cycle exercise at all work rates and permitted an equivalent stroke volume and stroke work from a smaller end-diastolic volume. The maximum increase in exercise EF in older subjects during NP infusion was equal to that in healthy, younger (22–39 yr) control subjects. The maximum cycle work rate and cardiac index were unchanged compared with placebo. Thus combined preload and afterload reduction with NP in older individuals improves overall LV ejection phase function: exercise LV stroke work is reduced, EF is increased, and stroke volume is maintained in the setting of a reduced ventricular size. These findings suggest that at least some of the age-associated decline in cardiac function during maximal aerobic exercise may be secondary to adverse loading conditions.
Age-related left ventricular function in the mouse: analysis based on in vivo pressure-volume relationships
Authors: Yang Bo , Larson Douglas F. , Watson Ronald
Published: December 2017

Our study compared left ventricular (LV) function between senescent and young adult mice through in situ pressure-volume loop analysis. Two groups of mice ( n = 9 each), 6-mo-old and 16-mo-old (senescent) mice, were anesthetized with urethan and α-chloralose, and their LV were instrumented with a Millar 1.4-Fr conductance micromanometer catheter for the acquisition of the pressure-volume loops. The senescent mice had a significantly decreased contractile function related to load-dependent parameters, including stroke volume index, ejection fraction, cardiac output index, stroke work index, and maximum derivative of change in systolic pressure over time. The load-independent parameters, preload recruitable stroke work and the slope (end-systolic volume elastance) of the end-systolic pressure-volume relationship, were significantly decreased in the senescent mice. Heart rate and arterial elastance were not different between the two groups; however, the ventricular-to-vascular coupling ratio (ratio of elastance of artery to end-systolic volume elastance) was increased by threefold in the senescent mice ( P < 0.001). Thus there were significant decreases in contractile function in the senescent mouse heart that appeared to be related to reduced mechanical efficiency but not related to arterial elastance.
Role of NO and K ATP + channels in adenosine-induced vasodilation on in vivo canine subendocardial arterioles
Authors: Yada Toyotaka , Hiramatsu Osamu , Tachibana Hiroyuki , Toyota Eiji , Kajiya Fumihiko
Published: December 2017

Adenosine (Ado) plays an important role in regulation of coronary vascular tone with nitric oxide (NO) and ATP-sensitive K+ [Formula: see text]) channels. In vitro, it was reported that subendocardial (Endo) arterioles are more sensitive to Ado than subepicardial (Epi) arterioles. The purpose of this study was to observe enhanced vasodilation of Endo arterioles directly and to evaluate possible roles of [Formula: see text] channels and NO in the different responses of Endo and Epi arterioles to Ado-induced vasodilation. We evaluated dilation of Endo and Epi arterioles (<120 μm) of beating canine hearts ( n = 19) by Ado (20 and 50 μg ⋅ kg−1 ⋅ min−1ic) before and after [Formula: see text] channel blockade (glibenclamide; 200 μg/kg ic), inhibition of NO synthase [ N G-nitro-l-arginine methyl ester (l-NAME); 30 μg ⋅ kg−1 ⋅ min−1, 20 min ic], or glibenclamide +l-NAME using a novel needle-probe CCD intravital microscope. Ado induced dose-dependent vasodilation in both Epi and Endo arterioles, but vasodilation was greater in Endo arterioles, i.e., increase at 120 s (maximum dilation) after Ado (50 μg ⋅ kg−1 ⋅ min−1) was 17% in Endo and 13% in Epi arterioles ( P < 0.01). Endo arteriole dilation was attenuated by blockade of [Formula: see text]channels from 18% (Ado) to 9% (Ado+glibenclamide) increase ( P < 0.001) and by inhibition of NO synthase from 17% (Ado) to 9% (Ado+l-NAME) ( P < 0.005). Epi arteriole vasodilation was attenuated by blockade of[Formula: see text] channels from 15 to 9% ( P < 0.005) and inhibition of NO from 16 to 10% ( P < 0.005). Suppression of vascular response was additive (Endo, 14 to −1%; Epi, 12 to 3%) with glibenclamide +l-NAME. We conclude that 1) the degree of Ado-induced vasodilation was greater in Endo than in Epi arterioles, with higher sensitivity of smaller arterioles in both layers and 2) transmural difference of arteriolar sensitivity to adenosine was abolished or reversed by[Formula: see text] channel blockade and/or by NO synthase inhibition, indicating crucial involvement of[Formula: see text] and NO in transmural sensitivity difference.
Ischemic preconditioning attenuates apoptosis through protein kinase C in rat hearts
Authors: Okamura Takayuki , Miura Toshiro , Iwamoto Hiroshi , Shirakawa Kazuyuki , Kawamura Shuji , Ikeda Yasuhiro , Iwatate Mitsuo , Matsuzaki Masunori
Published: December 2017

To investigate the role of protein kinase C (PKC) in the mechanism of ischemic preconditioning (IP), infarct size and the incidence of apoptosis caused by ischemia-reperfusion were tested in four groups of Sprague-Dawley rats. Dimethyl sulfoxide (vehicle) or calphostin C (0.1 mg/ml) was administered 5 min before the 30-min coronary occlusion followed by a 6-h reperfusion. Three cycles of 3 min of ischemia followed by 3 min of reperfusion was performed as IP before the 30-min ischemia followed by a 6-h reperfusion with or without calphostin C pretreatment. Infarct size defined by triphenyltetrazolium chloride staining was reduced from 60 ± 2 to 26 ± 2% by IP ( P < 0.01), but the effect of IP was abolished by calphostin C (51 ± 3%). Apoptosis defined by in situ terminal deoxynucleotidyl transferase end-labeling (TUNEL) was reduced by IP from 44 ± 3 to 13 ± 2% in the subendocardial region ( P < 0.01). This effect of IP was abolished by calphostin C (42 ± 8%). Thus the effect of IP on reducing the infarct size and the incidence of apoptosis are both mediated by PKC in rat hearts.
A hemodynamic analysis of coronary capillary blood flow based on anatomic and distensibility data
Authors: Kassab Ghassan S. , Le Kha N. , Fung Yuan-Cheng B.
Published: December 2017

An understanding of cardiac health and disease requires knowledge of the various factors that control coronary capillary blood flow. An analysis of coronary capillary blood flow based on a complete set of actual data on the capillary anatomy and elasticity does not exist. Previously, a complete set of data on the branching pattern and the vascular geometry of the pig coronary capillary network were obtained in our laboratory. In the present study, we obtained distensibility data on the coronary capillary blood vessels on the epicardial surface in the form of a pressure-diameter relationship using intravital microscopy. A mathematical model of the coronary capillary blood flow was then constructed on the basis of measured anatomic and elasticity data of the coronary capillary network, rheology of blood, physical laws governing blood flow, and appropriate boundary conditions. The constructed model was used to examine the heterogeneity of the spatial distribution of coronary blood flow, which is an important issue in coronary physiology. One interesting result of the model is that the dispersions of pressure and flow are significantly reduced in the presence of capillary cross-connections, and the resistance to flow is reduced as well. Finally, we found that the compliance of the epicardial surface capillary vessels is so small that its effect on the blood pressure drop is negligible in the diastolic state. However, the compliance of the intramyocardial capillaries remains unknown, and the interaction of the muscle contraction and blood vessel elasticity in systole remains to be studied.
Neuregulin activation of ErbB receptors in vascular endothelium leads to angiogenesis
Authors: Russell Kerry Strong , Stern David F. , Polverini Peter J. , Bender Jeffrey R.
Published: December 2017

The ErbB, or epidermal growth factor receptor (EGF-r), family of transmembrane tyrosine kinase receptors has been demonstrated to play an important role in growth regulation and intracellular signaling in a wide variety of cell types. Targeted deletion of neuregulin (an ErbB ligand) in mice results in endocardial cushion abnormalities, suggesting that these receptor-ligand interactions have important effects on vascular endothelial growth and development. To study the role of ErbB receptor signaling in vascular endothelium, we investigated the expression pattern of the various receptor family members and the effect of ErbB receptor stimulation in human umbilical vein endothelial cells (HUVEC). We demonstrate that ErbB2 (neu), ErbB3, and ErbB4 are highly expressed, whereas ErbB1 (EGF-r) is undetectable. Stimulation of HUVEC with recombinant neuregulin-β (an ErbB3/4 ligand) induces rapid calcium fluxes, receptor tyrosine phosphorylation, and cell proliferation. We demonstrate marked in vitro and in vivo angiogenic responses to neuregulin-β, which are independent of vascular endothelial cell growth factor. These findings support an important role for the ErbB family of receptors in endothelial cell signaling and function, including neuregulin-induced angiogenesis.
Modulation of endocardial natriuretic peptide receptors in right ventricular hypertrophy
Authors: Kim Sung Zoo , Cho Kyung Woo , Kim Suhn Hee
Published: December 2017

Natriuretic peptide (NP) receptors (NPRs) located at the endocardial endothelium are suggested to be involved in regulating myocardial contractility. However, the characteristics and modulation of NPRs in relation to cardiac failure are not well defined. This study examined the properties of NPRs in ventricular endocardium using quantitative receptor autoradiography, RT-PCR, Southern blot analysis, and activation of particulate guanylyl cyclase (GC) by NPs. In control rats, specific125I-labeled rat atrial NP (rANP)(1–28) binding sites were localized in right (RV) and left ventricular (LV) endocardium. Binding affinities of125I-rANP(1–28) were remarkably higher in RV than LV endocardium. Radioligand binding at these sites was mostly inhibited by des[Gln18,Ser19,Gly20,Leu21,Gly22]ANP(4–23), a specific NP clearance receptor ligand. mRNAs for all three recognized NPRs were detected in endocardial cells by RT-PCR and confirmed by Southern blot analysis. Production of cGMP by particulate GC in endocardial cell membranes was stimulated by NPs with a rank order of potency of C-type NP(1–22) >> brain NP (BNP)(1–26) > ANP(1–28). We also examined the modulation of these NPRs during cardiac hypertrophy induced by monocrotaline (MCT). In MCT-treated rats with pulmonary hypertension, specific125I-rANP(1–28) binding to hypertrophied RV endocardium almost disappeared and cGMP production by NPs was significantly decreased. In rats with pulmonary hypertension, plasma levels of ANP and BNP were increased by fivefold compared with controls. The results indicate that there is a differential distribution of NPRs in the cardiac chambers, with the most abundant binding sites in RV endocardium, that NPR-B is the predominant GC-coupled NPR in ventricular endocardium, and that endocardial NPRs are downregulated with ventricular hypertrophy. Downregulation of NPRs may be associated with an increment of endogenous NP production caused by mechanical overload in hypertrophied ventricle.
PKC translocation without changes in Gαqand PLC-β protein abundance in cardiac hypertrophy and failure
Authors: Jalili Thunder , Takeishi Yasuchika , Song Guojie , Ball Nancy A. , Howles Gabriel , Walsh Richard A.
Published: December 2017

Activation of protein kinase C (PKC) has been implicated as playing a key role in the pathogenesis of cardiac hypertrophy. This study investigates the response of several signal transduction proteins responsible for PKC activation during the transition from compensated pressure-overload hypertrophy (POH) to congestive heart failure (CHF). Pressure overload was produced on male, adult, Hartley strain guinea pigs using a ligature around the descending thoracic aorta. Sham-operated controls, POH, and CHF groups were identified based on left ventricular hypertrophy, pulmonary congestion, and isolated heart Langendorff mechanics. Quantitative immunoblotting revealed phospholipase C (PLC)-βI and Gαqwere unchanged during POH and CHF, as were RGS2, RGS3, and RGS4 (regulators of G protein signaling, which are activators of intrinsic GTPase activity). Translocation of PKC-α, -ε, and -γ from cytosolic to membranous fractions were significantly increased during POH and CHF. Cytosolic PKC activity was also elevated during POH. We conclude that differential PKC activation may be mediated by increases in Gαqand PLC-βI activity rather than upregulation of expression.
Estrogen improves acetylcholine-induced but not metabolic vasodilation in biological males
Authors: New Gishel , Duffy Stephen J. , Harper Richard W. , Meredith Ian T.
Published: December 2017

We have previously shown that chronic estrogen therapy improves endothelium-dependent vasodilation in the resistance vessels of biological males. Whether this is nitric oxide (NO) mediated and whether estrogen improves metabolic vasodilation is unknown. Resting forearm blood flow (FBF), ACh-induced vasodilation, and functional hyperemic blood flow (exercise) were assessed before and after the inhibition of NO with N G-monomethyl-l-arginine (l-NMMA) in 15 male-to-female transsexuals prescribed estrogen and in 14 age-matched males. Resting FBF was similar in the two groups and was similarly ( P = 0.44) but significantly reduced by 48% after infusion ofl-NMMA ( P < 0.0001). The ACh dose-response relationship was shifted upward and to the left in the transsexual compared with the male group ( P < 0.01). After the inhibition of NO, however, the difference in the ACh dose-response curve between the two groups was abolished ( P= 0.15). Peak functional hyperemic blood flow was similar for the two groups ( P = 0.94).l-NMMA produced a significant ( P < 0.01) but similar ( P = 0.64) reduction in peak hyperemia in the two groups. The volume of blood repaid to the forearm 1 and 5 min after exercise was also reduced by l-NMMA ( P < 0.0001); however, there were no differences between the two groups. This suggests that ACh-mediated NO-dependent vasodilation may be more sensitive to the effects of chronic estrogen than exercise-induced vasodilation. Long-term estrogen does not appear to improve exercise-induced metabolic vasodilation in biological males, despite the fact that NO contributes to this process.
Cardiopulmonary baroreceptor control of muscle sympathetic nerve activity in heat-stressed humans
Authors: Crandall C. G. , Etzel R. A. , Farr D. B.
Published: December 2017

Whole body heating decreases central venous pressure (CVP) while increasing muscle sympathetic nerve activity (MSNA). In normothermia, similar decreases in CVP elevate MSNA, presumably via cardiopulmonary baroreceptor unloading. The purpose of this project was to identify whether increases in MSNA during whole body heating could be attributed to cardiopulmonary baroreceptor unloading coincident with the thermal challenge. Seven subjects were exposed to whole body heating while sublingual temperature, skin blood flow, heart rate, arterial blood pressure, and MSNA were monitored. During the heat stress, 15 ml/kg warmed saline was infused intravenously over 7–10 min to increase CVP and load the cardiopulmonary baroreceptors. We reported previously that this amount of saline was sufficient to return CVP to pre-heat stress levels. Whole body heating increased MSNA from 25 ± 3 to 39 ± 3 bursts/min ( P < 0.05). Central blood volume expansion via rapid saline infusion did not significantly decrease MSNA (44 ± 4 bursts/min, P > 0.05 relative to heat stress period) and did not alter mean arterial blood pressure (MAP) or pulse pressure. To identify whether arterial baroreceptor loading decreases MSNA during heat stress, in a separate protocol MAP was elevated via steady-state infusion of phenylephrine during whole body heating. Increasing MAP from 82 ± 3 to 93 ± 4 mmHg ( P < 0.05) caused MSNA to decrease from 36 ± 3 to 15 ± 4 bursts/min ( P < 0.05). These data suggest that cardiopulmonary baroreceptor unloading during passive heating is not the primary mechanism resulting in elevations in MSNA. Moreover, arterial baroreceptors remain capable of modulating MSNA during heat stress.
S-T segment voltage during sequential coronary occlusions is an unreliable marker of preconditioning
Authors: Birincioglu Mustafa , Yang Xi-Ming , Critz Stuart D. , Cohen Michael V. , Downey James M.
Published: December 2017

During coronary angioplasty, a stair-step decrease in peak S-T segment elevation from the first to the second coronary occlusion has been assumed to indicate a preconditioning (PC) effect. This association was evaluated with myocardial electrograms in rabbits, which revealed that two sequential 5-min coronary occlusions resulted in a marked decrease in the area under the S-T segment voltage-time curve ( P < 0.05) with no change during a third occlusion. Pretreatment with either 5-hydroxydecanoate, a mitochondrial ATP-sensitive potassium (KATP) channel blocker, or anisomycin, an activator of stress-activated protein kinases, had no effect on the stair-step decline in the S-T segment voltage between the first two occlusions. HMR-1883, a potent closer of sarcolemmal KATP channels, abolished changes in S-T segment elevation after brief coronary occlusions but had no effect on the infarct-sparing property of the two preconditioning 5-min occlusions. Interestingly, HMR-1883 blocked myocardial protection from diazoxide, raising doubt that the latter opens only mitochondrial channels. Therefore, myocardial protection and S-T segment changes during ischemia are dissociated. These data suggest that it is the mitochondrial KATP channel that protects the myocardium, and it is the sarcolemmal channel that is responsible for changes in S-T elevation. Therefore, it cannot always be inferred that changes in S-T segment elevation reflect the state of myocardial protection.
Ischemic preconditioning prevents postischemic P-selectin expression in the rat small intestine
Authors: Davis Jon M. , Gute Dean C. , Jones Steven , Krsmanovic Aleksandra , Korthuis Ronald J.
Published: December 2017

Ischemic preconditioning (IPC) prevents the deleterious effects of prolonged ischemia and reperfusion (I/R). Because leukocyte infiltration is required to produce the microvascular dysfunction induced by I/R in the small intestine, and P-selectin-dependent leukocyte rolling is a requisite step in this process, we hypothesized that IPC would attenuate postischemic P-selectin expression. To address this postulate, P-selectin expression was evaluated in nonischemic (control) rat jejunum and in rat jejunum subjected to I/R alone (20 min ischemia/60 min reperfusion), or IPC (5 min ischemia/10 min reperfusion) + I/R using a dual radiolabeled monoclonal antibody approach. I/R was associated with a sevenfold increase in jejunal P-selectin expression, an effect that was completely abolished by IPC. Exposing the bowel to adenosine deaminase or an adenosine A1, but not an A2, receptor antagonist during the period of preconditioning ischemia or to selective PKC antagonists during prolonged ischemia prevented the beneficial effect of IPC to limit I/R-induced P-selectin expression. Our data indicate that P-selectin expression is a novel downstream effector target of the adenosine-initiated, PKC-dependent, anti-inflammatory signaling pathway in IPC.