bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of stimulation of phosphoinositide hydrolysis by alpha 1-adrenergic agonists in adult rat hearts
Authors: Lazou A. , Fuller S. J. , Bogoyevitch M. A. , Orfali K. A. , Sugden P. H.
Published: December 2017

The coupling of the pharmacologically defined alpha 1A- and alpha 1B-adrenoceptors to the hydrolysis of phospho[3H]inositides (PI) was investigated in ventricular myocytes freshly isolated from adult rat hearts. The alpha 1-adrenoceptor population in the heart was characterized by competitive binding experiments using [3H]prazosin and the alpha 1A-adrenoceptor-selective antagonist 5-methyl urapidil. It was heterogeneous with approximately 25% being pharmacologically of the alpha 1A-adrenoceptor subtype and 75% being of the alpha 1B-adrenoceptor subtype. Epinephrine, norepinephrine, or phenylephrine stimulated PI hydrolysis in the presence or absence of propranolol. The greatest stimulation (7-fold) was with epinephrine. The half-maximum effective concentrations for agonists were approximately 0.5-3.5 and 0.2 microM in the absence and presence of propranolol, respectively. The inhibition by 5-methyl urapidil of the stimulation of PI hydrolysis by a fixed concentration of epinephrine fitted a two-site competition curve. The distribution between high-affinity (25%) and low-affinity (75%) sites suggested that both the alpha 1A- and alpha 1B-adrenoceptors were coupled to PI hydrolysis in proportion to their relative abundance. Equally, the stimulation of PI hydrolysis by epinephrine in the presence of a fixed concentration of 5-methyl urapidil was biphasic. In addition, chloroethylclonidine, an irreversible inhibitor of the alpha 1B-adrenoceptor, inhibited the epinephrine stimulation of PI hydrolysis by 35%. We conclude that the pharmacologically defined alpha 1A- and alpha 1B-adrenoceptor subtypes are both coupled to PI hydrolysis in the ventricular myocyte.
Contraction-excitation feedback in atrial reentry: role of velocity of mechanical stretch
Authors: Yamashita T. , Oikawa N. , Murakawa Y. , Nakajima T. , Omata M. , Inoue H.
Published: December 2017

To determine the effects of atrial stretch on atrial flutter, we analyzed variations in atrial flutter cycle length (CL) caused by ventricular contraction in five dogs with artificially induced atrioventricular block. In contrast to absence of variations in CL during sustained ventricular asystole, atrial stretch by ventricular contraction consistently produced phasic variations in CL. The variations were not confined to any specific atrial sites, but depended on the time of ventricular contraction relative to atrial activation phase. The phase-response curve of the variations was closely related to that of the velocity of changes in the atrial pressure with no time lags, but not to that of the atrial pressure itself. Pharmacological denervation did not abolish the variations. Conventional electrophysiological study revealed greater changes in intra-atrial activation time by atrial stretch at a short pacing cycle length than at a longer one, suggestive of changes in repolarization by mechanical stretch. In conclusion, atrial stretch caused by ventricular contraction produces phasic variations in CL, the extent of which depends on the velocity of the mechanical stretch of atrial muscles.
Myocardial function and metabolism in pig hearts after relief from chronic partial coronary stenosis
Authors: Liedtke A. J. , Renstrom B. , Nellis S. H. , Subramanian R.
Published: December 2017

Metabolic behavior was compared during acute extracorporeal reperfusion after removal of a chronic 4-day partial coronary stenosis in eight pig hearts (RCS group) and during comparable extracorporeal perfusion in seven chronically prepared hearts (Sham group). Coronary stenosis in RCS hearts was induced in the left anterior descending (LAD) artery by partial inflation of a hydraulic occluder to restrict LAD peak phasic velocity by approximately 50%. Regional mechanical shortening was decreased in RCS compared with Sham hearts after 4 days of chronic coronary stenosis [diminished systolic shortening (P < 0.066) with systolic expansion (P < 0.015)] but was comparable to Sham hearts after relief from stenosis. At analogous workloads (left ventricular pressure and heart rate) during reperfusion, metabolic behavior was distinctive between groups. Specifically, compared with Sham hearts, myocardial O2 consumption was selectively increased in RCS hearts (+ 49 delta %, P < 0.026) as was fatty acid oxidation estimated from 14CO2 production from [U-14C]palmitate (+ 60 delta %, P < 0.061) and exogenous glucose utilization measured from the release of 3H2O from [5-3H]glucose (+ 517 delta %, P < 0.025). At the conclusion of the studies, triphenyltetrazolium chloride staining showed no gross evidence of macroinfarction in RCS or Sham hearts, and there was an essentially unremarkable histological survey of anterior myocardium for microscopic necrosis in either group. The level of O2 consumption and preservation of preferred fatty acid utilization indicate that metabolism remains or regains its aerobic pattern of activity in early recovery immediately after removal of chronic partial coronary stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)
Leukocyte adhesion, edema, and development of postischemic capillary no-reflow
Authors: Jerome S. N. , Akimitsu T. , Korthuis R. J.
Published: December 2017

The aim of this study was to determine whether the formation of edema that occurs secondary to the neutrophil-dependent increase in microvascular permeability contributes to the genesis of no-reflow in postischemic skeletal muscle. To address this issue, four experimental approaches were used. In the first group, capillary perfusion was assessed in nonischemic canine gracilis muscles in which interstitial fluid volume was increased to a level similar to that in postischemic muscle. In the second and third groups, edema formation was prevented in postischemic skeletal muscles by administration of phalloidin or a hypertonic hyperosmotic saline-dextran solution (HSD; 7.5% saline-6% Dextran 70), and the extent of capillary no-reflow was assessed. In the final group of experiments, a monoclonal antibody (MAb) that binds to the common beta-subunit of the leukocyte integrin CD11/CD18 (MAb IB4) was administered after the development of postischemic edema, and capillary perfusion was determined. Formation of edema in nonischemic preparations and ischemia-reperfusion (I-R) were associated with marked reduction in the number of patent capillaries per fiber (1.2 +/- 0.1 and 0.4 +/- 0.1, respectively) compared with nonedematous nonischemic controls (2.5 +/- 0.3). Treatment with phalloidin or HSD prevented edema formation and attenuated the reduction in the number of patent capillaries per fiber (1.62 +/- 0.2 and 1.71 +/- 0.2, respectively) induced by I-R, whereas administration of MAb IB4 after the formation of edema in reperfused muscles failed to limit capillary no-reflow (0.5 +/- 0.1 patent capillaries/fiber).(ABSTRACT TRUNCATED AT 250 WORDS)
Effects of hypertension and aging on fibronectin expression in aorta of Dahl salt-sensitive rats
Authors: Takasaki I. , Takizawa T. , Sugimoto K. , Gotoh E. , Shionoiri H. , Ishii M.
Published: December 2017

Effects of hypertension and aging on aortic fibronectin expression were investigated in male Dahl salt-sensitive (Dahl-S) and salt-resistant (Dahl-R) rats fed either a low- or high-salt diet from 5 to 37 wk of age. In comparison to low-salt controls, the steady-state mRNA levels for aortic fibronectin in salt-loaded Dahl-S rats were dramatically increased at 37 wk of age, corresponding to a severe stage of hypertension with high mortality, whereas at earlier ages representing early to established phases of hypertension, no significant changes were observed. Salt loading affected neither blood pressure nor aortic fibronectin expression in Dahl-R rats. Aging without coexisting hypertension did not cause significant changes in aortic fibronectin mRNA levels all through the study period in either strain of rats. These results suggest that aortic fibronectin may be strongly regulated by factors associated with severe hypertensive organ damages caused by long-standing hypertension in salt-loaded Dahl-S rats. Also suggested was that aortic fibronectin may not play a major role in the pathogenesis of early aortic changes occurring in response to hypertension or as a process of aging.
Gender difference in cardiopulmonary reflex inhibition of sympathetic nerve activity
Authors: Scislo T. J. , DiCarlo S. E.
Published: December 2017

We tested the hypothesis that reflex responses to mechanical [increase in left atrial pressure (LAP) 0-25 mmHg] and chemical stimulation [left atrial injection of phenylbiguanide (PBG), 0.5-10 mg/kg] of cardiopulmonary receptors are greater in female (n = 9; 335 +/- 9 g) than in male (n = 10; 558 +/- 23 g) age-matched rats. Anesthetized (500 mg/kg urethan and 80 mg/kg alpha-chloralose), tracheotomized, and artificially ventilated (100% oxygen), sinoaortic-denervated animals were instrumented with left atrial, femoral venous, and arterial catheters and a Tygon occluder around the ascending aorta. Reflex inhibition of lumbar sympathetic nerve activity (LSNA) vs. LAP and dose PBG was higher in female rats. A two-way analysis of variance revealed a significant gender effect, males vs. females (P = 0.023), and a significant gender x dose interaction (P < 0.001) for LSNA vs. LAP. There was also a significant gender x dose interaction (P < 0.001) for LSNA vs. PBG. However, there was no influence of gender on the reflex inhibition of mean arterial pressure (P = 0.751) or heart rate (P = 0.561). These responses were associated with a higher left ventricular weight-to-body weight ratio in females (2.14 +/- 0.06 vs. 1.95 +/- 0.07 g/kg, P = 0.039).
Computer model of membrane current and intracellular Ca2+ flux in the isolated guinea pig ventricular myocyte
Authors: Nordin Charles
Published: December 2017

Pages H2117–H2136: Nordin, Charles. “Computer model of membrane current and intracellular Ca2+ flux in the isolated guinea pig ventricular myocyte.”

Figure 13: Units of time in Fig. 13B are seconds (not milliseconds). The output for concentration, using the equations of the appendix, is in units of 10−3 mol/l (millimolar). Equation A29 should read (See PDF) Equations A30a and A31a should read (See PDF)

Note: All errors in equations, except for the term with asterisk in Eq. A31a and removal of the term (0.1 x iCa) from Eq. A30a, were made in transcribing the computer program to the set of printed equations and therefore do not involve any simulations of the paper. The other changes are refinements of the program that slightly reduce the rise in [Na+]myo and fall in [K+]myo with increasing stimulation rate (Fig. 5A) but do not affect other aspects of the behavior of the model in any significant way.
Effect of ryanodine on the initiation and perpetuation of stretch-induced arrhythmias in isolated canine ventricle
Authors: Jobe R. L. , Taylor L. K. , Wang Z. , Berger C. M. , Stacy G. P. , Hansen D. E.
Published: December 2017

Ventricular arrhythmias can be initiated by a mechanism of transient diastolic dilation. To test the hypothesis that Ca2+ release from sarcoplasmic reticulum (SR) is important in initiation of such stretch-induced arrhythmias (SIAs), we studied effects of ryanodine in an isolated canine heart model. Arrhythmias were induced by a computerized ventricular volume servo-pump system that transiently increased left ventricular volume by precise amounts (delta V) during diastole. The probability of eliciting an SIA (PSIA) was compared at the minimum delta V that resulted in PSIA of >5 or = 90% under baseline conditions. Block of SR Ca2+ release with 10(-5) M ryanodine in 11 ventricles produced mild inhibition of SIAs, reducing PSIA by 19.4% (P = 0.039). Because ryanodine produces leakage of SR Ca2+ at low concentration and block of SR Ca2+ release at high concentration, ryanodine concentration was varied from 10(-9) to 10(-5) M in six ventricles. Ryanodine had minimal effect on PSIA over this concentration range. In six ventricles with elevated intracellular Ca2+ produced by pretreatment with 0.1-0.3 microM strophanthidin, 10(-5) M ryanodine did not significantly reduce PSIA. Probability of inducing ventricular pairs or nonsustained ventricular tachycardia was greater in strophanthidin-treated ventricles than in controls, but induction of these repetitive ventricular beats in the strophanthidin group was virtually abolished by addition of 10(-5) M ryanodine.(ABSTRACT TRUNCATED AT 250 WORDS)
Kinetics of the sarcolemmal lactate carrier in single heart cells using BCECF to measure pHi
Authors: Wang X. , Levi A. J. , Halestrap A. P.
Published: December 2017

The pH-sensitive fluorescent indicator 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) was used to measure lactate transport in single cardiac myocytes. Addition of lactate externally caused a rapid fall of intracellular pH (pHi), which was largely inhibited by 5 mM alpha-cyano-4-hydroxycinnamate (CHC), a specific inhibitor of the lactate carrier. Stilbene disulfonates such as 4,4'-dibenzamidostilbene-2,2'-disulfonate (DBDS) only partially inhibited the response, with inhibition being greater in guinea pig than rat myocytes. The data are consistent with two isoforms of the lactate carrier, one sensitive and one insensitive to DBDS, coexisting within a single myocyte and both having a stoichiometry of 1 lactate:1 proton. The initial rate of pHi fall was used to determine carrier kinetics. Rat myocytes had a Michaelis constant (Km) for external L-lactate of 2.74 mM and a Km for external pyruvate of 0.2 mM. Guinea pig cells had a Km for external L-lactate of 2.2 mM. Kinetics of lactate efflux were also evaluated using the rate of pHi recovery on removing external lactate. The Km and maximal rate values for efflux were both threefold higher than for influx and were related to each other and the transmembrane pH gradient as predicted by the Haldane relationship. It is suggested that under hypoxic conditions, the carrier may be the rate-limiting factor for lactate extrusion.
Relaxant effects of isoproterenol in isolated cardiac muscle: influence of loading patterns
Authors: Suard I. , Pery-Man N. , Coirault C. , Pourny J. C. , Lecarpentier Y. , Chemla D.
Published: December 2017

The purpose of this study was to test the hypothesis that loading patterns (i.e., loading sequence, total load, and preload) modulate the relaxant effects of isoproterenol. The effects of isoproterenol (10(-6) M) on peak rate of force decline (-dF/dt) were studied in rat left ventricular papillary muscle (n = 24) with respect to two sequences of relaxation: the classical, isotonic-isometric sequence, in which tension fall occurs at initial muscle length, and the physiological, isometric-isotonic sequence, in which tension fall occurs at end-systolic muscle length. The influences of muscle load and initial length were accounted for in the evaluation of relaxation rate by plotting -dF/dt against the entire range of loads both at preload = maximum length (Lmax) and 90% Lmax. The main results are the following: 1) in the classical, isotonic-isometric sequence of relaxation, and whatever the preload, the magnitude of the relaxant effect of isoproterenol increased with load; 2) after reversal into the physiological, isometric-isotonic sequence of relaxation, the relaxant effect of isoproterenol behaved independently of load level in muscle preloaded at Lmax; 3) conversely, in muscle preloaded at 90% Lmax and relaxing according to the physiological sequence, the relaxant effect of isoproterenol increased with load; and 4) the peak relaxant effect of isoproterenol was proportionally higher in the physiological sequence of relaxation than in the classical one and occurred at a similar level of load, whatever the loading sequence and whatever the preload level. Our results indicate that loading patterns finely modulated the relaxant effects of isoproterenol and that muscle length, both before the contraction phase and at the onset of relaxation phase, influenced the effects of isoproterenol on myocardial relaxation rate.
Determinants of end-systolic pressure during different load alterations in the in situ left ventricle
Authors: van der Linden L. P. , van der Velde E. T. , van Houwelingen H. C. , Bruschke A. V. , Baan J.
Published: December 2017

Because of the strong dependency of the end-systolic pressure-volume relation on the type of transient loading intervention in the in situ left ventricle (LV), experiments in the basal inotropic state in 16 open-chest anesthetized dogs were reanalyzed to find additional variables to model and predict end-systolic pressure (ESP) of both afterloading and preloading interventions by a single equation. Random-coefficients regression analysis was performed on 22 experiments in the basal inotropic state simultaneously, yielding an overall R2 of 0.97. The major part of total variance of ESP was due to linear terms of end-systolic volume (ESV) (74%) and stroke volume (SV) (19%). The SV effect was consistently negative and quantitatively quite important. An average load-independent end-systolic elastance of 6.7 mmHg/ml and an average SV effect of -5.7 mmHg/ml ejected were estimated, separating the “force-length” property from shortening effects in the in situ LV. History-related effects appeared to be only minor.
Capillary hemodynamics in hemorrhagic shock and reperfusion: in vivo and model analysis
Authors: Mazzoni M. C. , Warnke K. C. , Arfors K. E. , Skalak T. C.
Published: December 2017

A computer network model and in vivo measurements of microcirculatory blood flow in skeletal muscle were used to study the mechanisms responsible for low flow in hemorrhagic shock and reperfusion, with focus on the potential importance of capillary diameters and leukocyte rheology. Model flows were determined by the network pressure gradient, systemic hematocrit and leukocrit, leukocyte cytoplasmic viscosity, and vessel dimensions. After 1 h of shock (40% acute bleed) in anesthetized rabbits, pressure was reduced by 45%, hemodilution occurred, and capillary diameters decreased by 21%. The 45–50% flow reduction found experimentally in gastrocnemius muscle by laser Doppler flowmetry (LDF) and a microsphere technique matched model flow predictions with one-half of the proximal capillaries narrowed. Ringer-lactate (RL) reperfusion only partially restored control LDF flow, whereas a small-volume bolus of hypertonic saline-dextran followed by RL gave complete LDF flow recovery. The model predicted these flows for moderate hemodilution states, with the added insight that low-flow conditions are exacerbated by leukocytes only if they become activated, which is often a complication in ischemia/reperfusion.
Effects of peroneal nerve stimulation on hypothalamic stimulation-induced ventricular arrhythmias in rabbits
Authors: Zhou X. , Wolf P. D. , Smith W. M. , Blanchard S. M. , Ideker R. E.
Published: December 2017

We tested the hypothesis that peripheral afferent nerve stimulation decreases the incidence of ventricular arrhythmias induced by central nervous system stimulation. The hypothalamus in each of 24 anesthetized rabbits (12 with anterior myocardial ischemia) was electrically stimulated for 10 s with 10-min intervals between each of six consecutive stimulation episodes. The left peroneal nerves were electrically stimulated for 15 min beginning 5 min after the second hypothalamic stimulation episode in six ischemic and six nonischemic rabbits. Cardiac rhythm was monitored with the electrocardiogram lead I and atrial and ventricular electrograms. Hypothalamic stimulation alone induced ventricular arrhythmias [mean no. of arrhythmic beats occurring during 3rd and 4th hypothalamic stimulation episodes: nonischemic animals, 20 +/- 8; ischemic animals, 62 +/- 41 (P < 0.05 by unpaired t-test)]. Peroneal nerve stimulation reduced the number of arrhythmic beats induced by hypothalamic stimulation in nonischemic animals (6 +/- 5; P < 0.05 vs. without peroneal stimulation) and prevented an increase in arrhythmic beats during ischemia (21 +/- 16). Thus peripheral nerve stimulation decreased the number of ventricular arrhythmic beats induced by repeated hypothalamic stimulation in both ischemic and normal rabbit hearts and may be important in the prevention of arrhythmias in patients.
Effects of endothelium-derived nitric oxide on skin and digital blood flow in humans
Authors: Coffman J. D.
Published: December 2017

The effects of NG-monomethyl-L-arginine (L-NMMA) on total finger and forearm, and dorsal finger and forearm skin, blood flows were studied in the basal state and during reflex sympathetic vasoconstriction in normal subjects. Total flows were measured by venous occlusion plethysmography and skin flows by laser-Doppler flowmetry (LDF). L-NMMA in doses of 2, 4, and 8 microM/min given by constant infusion via a brachial artery catheter significantly decreased finger blood flow, forearm blood flow, and vascular conductances. At 8 microM/min, total finger blood flow decreased 38.4% and forearm blood flow decreased 24.8%. Dorsal finger and forearm skin LDF were also significantly decreased (25 and 37% at 8 microM/min). Body cooling significantly decreased finger blood flow (73.6%), vascular conductance, and finger LDF (59.7%). L-NMMA had no effect on total finger blood flow or dorsal finger LDF during body cooling. Nitric oxide or related compounds contribute to the basal dilator tone of the dorsal finger and forearm skin but not during reflex sympathetic vasoconstriction.
Use of MQAE for measurement of intracellular [Cl-] in cultured aortic smooth muscle cells
Authors: Koncz C. , Daugirdas J. T.
Published: December 2017

A novel fluorescent indicator, N-[ethoxycarbonylmethyl]-6-methoxy-quinolinium bromide (MQAE), was used to measure intracellular chloride concentration ([Cl-]i) in primary cultures of rat aortic smooth muscle cells (VSMC). The hydrolytic and fluorescent properties of the dye were characterized. The intracellular Stern-Volmer constant was calculated to be 25 M-1. Cl- efflux curves were characteristic of saturation-type kinetics, with an apparent Michaelis-Menten constant value of 11 +/- 4.8 (SD) mM, a maximum velocity of 0.038 +/- 0.021 mM/s, and a half time (t1/2) of 9.0 +/- 3.7 min. The average efflux rate in the first 10 min (0.023 +/- 0.004 mM/s) was reduced in the presence of either 130 microM 4,4'-diisothiocyanato-dihydrostilbene-2,2'-disulfonic acid (H2DIDS) (0.014 +/- 0.006, P = 0.02) or 40 microM furosemide (0.017 +/- 0.004, P = 0.04). Restoration of physiological extracellular chloride concentration ([Cl-]o) after zero Cl- resulted in net Cl- influx with a t1/2 of 3.6 +/- 1.0 min. The initial Cl- influx rate was reduced after exposure to furosemide, from 0.069 +/- 0.006 to 0.046 +/- 0.008 mM/s, P < 0.002, and was reduced after exposure to H2DIDS from 0.102 +/- 0.013 to 0.033 +/- 0.003 mM/s, P < 0.001. Furosemide reduced the steady-state [Cl-]i from 31.6 +/- 3.2 to 26.1 +/- 2.4 mM, P < 0.01, whereas H2DIDS had little effect on [Cl-]i. Our results demonstrate that MQAE can be used to measure [Cl-]i in primary cultures of VSMC.
Sialyl Lewisx-containing oligosaccharide exerts beneficial effects in murine traumatic shock
Authors: Skurk C. , Buerke M. , Guo J. P. , Paulson J. , Lefer A. M.
Published: December 2017

We investigated the effects of a soluble sialyl Lewisx-containing oligosaccharide (SLex-OS) in a rat model of traumatic shock. Pentobarbital-anesthetized rats subjected to Noble-Collip drum trauma developed a shock state characterized by marked hypotension, a survival time of 85 +/- 15 min, significant increases in ileal myeloperoxidase (P < 0.01), and plasma free amino-nitrogen activities (P < 0.01). Treatment with SLex-OS (10 mg/kg) 10 min posttrauma prolonged survival time to 198 +/- 29 min (P < 0.01), significantly attenuated ileal myeloperoxidase activity (P < 0.01), and diminished the accumulation of plasma free amino-nitrogen (P < 0.01), drug vs. vehicle, respectively. Furthermore, endothelium-dependent relaxation to acetylcholine in superior mesenteric artery rings isolated from SLex-OS-treated shock rats was significantly preserved (70 +/- 6 vs. 40 +/- 5% relaxation). No beneficial effects were observed using a nonfucosylated control oligosaccharide. Moreover, addition of SLex-OS significantly inhibited unstimulated human polymorphonuclear neutrophil (PMN) adherence in vitro to trauma-activated superior mesenteric artery endothelium ex vivo (P < 0.001). Our results indicate that SLex-OS exerts beneficial effects in traumatic shock states by blocking selectin-mediated leukocyte-endothelium interaction, thus improving survival, attenuating intestinal PMN accumulation, and diminishing shock-induced tissue injury.
Role of endothelin-1 in neointima formation after endothelial removal in rabbit carotid arteries
Authors: Azuma H. , Hamasaki H. , Niimi Y. , Terada T. , Matsubara O.
Published: December 2017

To investigate the role of local endothelin (ET)-1 in neointima formation, we performed a balloon denudation in the rabbit carotid artery. Four weeks after denudation, regeneration of endothelial cells was almost complete, and a marked intimal hyperplasia was observed. The tissue level of ET-1-like immunoreactivity was significantly increased even at 24 and 72 h after denudation and was 9.3 times higher than the control group in 4 wk. On the same time course, the proliferating cell nuclear antigen (PCNA)-positive cells clearly appeared. Receptor density values for 125I-ET-1 and 125I-IRL-1620 [ET-receptor subtype B (ETB)-selective ligand] bindings were significantly greater in the hyperplastic artery without changes in dissociation equilibrium constant values. The 125I-ET-1 binding sites not inhibited with BQ-123 [ET-receptor subtype A (ETA)-selective antagonist] were significantly increased in hyperplastic arteries. ETB receptors were more densely localized in the neointima. The chronic intravenous administration of BQ-123 at plasma concentrations sufficient to antagonize the ETA receptors had no effect on neointima formation and the appearance of PCNA-positive cells. We concluded from all results that ET-1 would be involved in neointima formation after endothelial removal and that the ETA receptors would not play a role in this process.
Ebselen protects against ischemia-reperfusion injury in a canine model of myocardial infarction
Authors: Hoshida S. , Kuzuya T. , Nishida M. , Yamashita N. , Hori M. , Kamada T. , Tada M.
Published: December 2017

We investigated the infarct-limiting effect of a selenoorganic compound, ebselen [2-phenyl-1,2-benzisoselenazol-3(2H)-one], in a canine coronary artery occlusion-reperfusion model of myocardial infarction. Ebselen, administered 1 h before coronary artery occlusion (50 mg/kg po), significantly reduced infarct size resulting from 90-min coronary artery occlusion followed by 5-h reperfusion (P < 0.05). When we examined the relation between infarct size and plasma ebselen level, infarct size in dogs with plasma ebselen level > 5 microM before reperfusion was significantly smaller (P < 0.05) than that in dogs with plasma ebselen level < or = 5 microM or in the control dogs. This infarct limitation produced by ebselen treatment was associated with an increase in reduced glutathione content and a reduction in myeloperoxidase activity in the ischemic myocardium. No differences between the control and treated groups were found in hemodynamic parameters or regional myocardial blood flow in the course of the experiment. The findings of this study demonstrate that ebselen effectively reduced the myocardial ischemia-reperfusion injury associated with preservation of the glutathione redox state and a reduction in neutrophil infiltration into the ischemic myocardium.
Chloride and cation currents activated by bradykinin in coronary venular endothelial cells
Authors: Song J. , Davis M. J.
Published: December 2017

Bradykinin (BK) is known to activate several types of ion channels in endothelial cells, including a K+ channel and a nonselective cation channel. The predominant BK-activated current in most endothelial cells appears to be an outward, Ca(2+)-activated K+ current. We consistently recorded a rapidly activated, spontaneously inactivated inward current stimulated by BK in bovine coronary venular endothelial cells (CVECs). With the use of a whole cell, perforated patch recording mode, the average magnitude of the current was -293 +/- 38 pA. Simultaneous measurements of current and intracellular Ca2+ concentration ([Ca2+]i) showed that the inward current correlated closely with transient increases in [Ca2+]i due to Ca2+ release from intracellular stores. The current could be blocked by 4,4'-diisothiocyanatostilbene-2, 2'-disulfonic acid (DIDS) but not by La3+, and it persisted in Ca(2+)-free/Na(+)-free solution. When intra- and/or extracellular Cl- concentrations were altered, the reversal potential of the current shifted according to the calculated Cl- -equilibrium potential, indicating that the current was carried primarily by Cl-. Another inward current was also activated by BK. This current was slower to activate, could be blocked by La3+, but was not blocked by DIDS. The time course of the slowly activated current correlated with the plateau phase of the BK-stimulated [Ca2+]i increase, which was similar to the behavior of a nonselective cation current reported previously. We propose that these two currents may contribute to the depolarizations and net inward currents induced by BK in this cell line.
Transarterial wall oxygen gradients at the dog carotid bifurcation
Authors: Santilli S. M. , Stevens R. B. , Anderson J. G. , Payne W. D. , Caldwell M. D.
Published: December 2017

The purpose of this study was to determine the effect of the carotid artery bifurcation on the delivery of oxygen to the artery wall by measuring the transarterial wall oxygen gradient. Transarterial wall oxygen gradient measurements were performed in dogs anesthetized with thiopental sodium and isoflurane by means of an oxygen microelectrode. Measurements were performed at six locations along the carotid bifurcation. Oxygen tensions at the carotid sinus were decreased in the inner 40% of the artery wall compared with control locations. Oxygen tensions at the flow divider were increased throughout the artery wall compared with control locations. These effects were noted without differences in blood pressure, arterial blood oxygen tension, or histological evidence of atherosclerotic lesion formation. These findings suggest that the delivery of oxygen to the artery wall is altered by the bifurcation of the carotid artery. Low arterial oxygen tensions at the carotid sinus support a role for artery wall hypoxia in the formation of atherosclerotic lesions.
Impact of cardiopulmonary bypass and cardioplegic arrest on myocardial lymphatic function
Authors: Mehlhorn U. , Davis K. L. , Burke E. J. , Adams D. , Laine G. A. , Allen S. J.
Published: December 2017

Cardioplegic arrest (CPA) is associated with interstitial myocardial edema, which has been shown to impair myocardial function. The accumulation of interstitial myocardial edema may be enhanced by impaired myocardial lymph flow. The purpose of this study was to investigate the effects of CPA on myocardial lymphatic function. In nine anesthetized dogs, we cannulated a prenodal cardiac lymphatic and measured myocardial lymph flow rate (QL), myocardial lymph driving pressure (PL), and myocardial lymph hyaluronan (Hya) concentration. We determined left ventricular function using pressure-volume curves derived by sonomicrometry and micromanometry. The dogs were placed on cardiopulmonary bypass (CPB) (28 degrees C) and subjected to 60 min of hypothermic, crystalloid CPA. With the onset of asystole both QL and PL decreased significantly from 70.7 +/- 31.8 (SD) to 3.3 +/- 4.0 microliters/min and from 19.9 +/- 8.0 to 10.4 +/- 1.8 mmHg, respectively (P < 0.01). Following return of sinus rhythm after separation from CPB, QL and PL increased significantly to 135.4 +/- 28.0 microliters/min and 27.3 +/- 7.5 mmHg, respectively (P < 0.01). Post-CPA myocardial edema was demonstrated by gravimetric wet-to-dry weight determination of 3.67 +/- 0.20 (normal 2.90 +/- 0.20, P < 0.001) and was associated with significantly decreased left ventricular function. Myocardial Hya turnover rate was 1.3 +/- 1.0% per day under baseline conditions and increased significantly to 2.7 +/- 0.9% per day post-CPA (P < 0.01). We conclude that organized myocardial contraction is the major determinant of myocardial lymph flow. Myocardial lymph flow impairment during CPA may contribute to post-CPA myocardial edema and left ventricular dysfunction.
Characterization and pH dependence of L-glutamate transport in sarcolemmal vesicles from rat hearts
Authors: Dinkelborg L. M. , Kinne R. K. , Grieshaber M. K.
Published: December 2017

Transport of L-glutamate in purified sarcolemmal vesicles from rat heart was Na+ dependent and characterized by an apparent affinity value of 0.149 +/- 0.04 mM (n = 6). Na+ binding to the carrier was not very specific, since an inwardly directed K+ gradient could also increase vesicular uptake of L-glutamate. Uptake of L-glutamate into sarcolemmal vesicles was inhibited by L-aspartate and L-cysteinate. These characteristics of glutamate uptake are typical of transport via system XAG-. Acidification of either the intravesicular or the extravesicular space led to a significant increase in L-glutamate transport. This increase was more pronounced when the intravesicular space had been acidified. Thus intracellular acidosis of hypoxic or ischemic myocardium is directly linked to an increased uptake of glutamate.
Dissociation between anti-infarct effect and anti-edema effect of ischemic preconditioning
Authors: Sanz E. , Garcia Dorado D. , Oliveras J. , Barrabes J. A. , Gonzalez M. A. , Ruiz-Meana M. , Solares J. , Carreras M. J. , Garcia-Lafuente A. , Desco M. , et al.
Published: December 2017

This study tested the hypothesis that preconditioning, by reducing catabolite accumulation during ischemia, reduces osmotic swelling and myocardial necrosis during subsequent reperfusion. Farm pigs were randomly allocated to one of three groups of treatment: a control group undergoing a 48-min coronary occlusion (CO) of the middle left anterior descending artery, a preconditioned group (2 cycles of 5-min CO and 5-min reperfusion before the 48-min CO), or an intracoronary perfusion group receiving a substrate-free anoxic buffer perfusion into the area at risk between minutes 5 and 10 of the prolonged CO. Animals were killed after 30 min (n = 23) or 6 h (n = 31) of reperfusion. Compared with the control group, both ischemic preconditioning and washout of ischemic by-products by transient anoxic perfusion reduced myocardial edema after 30 min of reperfusion (P < 0.002) by 35 and 32%, respectively, but only ischemic preconditioning reduced final infarct size (by 55%, P < 0.006). Myocardial lactate content before reperfusion, measured in an additional series of 12 experiments, was reduced by 35% in animals receiving preconditioning or intracoronary perfusion. Thus ischemic preconditioning has a marked protective effect against reperfusion edema, and this effect can be explained by reduced catabolite accumulation during ischemia. However, there is no evidence from this study indicating that reduced catabolite accumulation and limited reperfusion edema explain the important anti-infarct effect of ischemic preconditioning.
Modulation of contractions to and receptors for endothelins in canine veins
Authors: Miller V. M. , Michener S. R.
Published: December 2017

Experiments were designed to characterize endothelin receptors in canine femoral veins and to determine whether their distribution or sensitivity could be altered by chronic changes in blood flow and oxygen tension in veins proximal to an arteriovenous fistula. Endothelium was removed from unoperated or fistula-operated femoral veins of anesthetized dogs. Veins were cut into rings and suspended in organ chambers for the measurement of isometric force or frozen for isolation of membrane proteins. Endothelin-1, endothelin-3, and sarafotoxin S6c caused concentration-dependent increases in tension in all rings. In rings of unoperated veins, maximal tensions were significantly less to endothelin-3 and sarafotoxin S6c than to endothelin-1. In rings of fistula-operated veins, maximal tensions to endothelin-1 and endothelin-3 were the same. Contractions to endothelin-1 or endothelin-3 in unoperated veins were not inhibited by an antagonist of endothelin-A receptors, BQ-123. Binding of 125I-labeled endothelin-1 (125I-endothelin-1) to membranes from veins without endothelium increased as a function of membrane protein. Affinity of receptors, as determined by competitive inhibition of 125I-endothelin-1 was as follows: endothelin-1 > endothelin-3 > sarafotoxin S6c. Competitive inhibition of 125I-endothelin-1 by endothelin-3 and sarafotoxin S6c was significant for a two-site binding model in all veins. The total number of binding sites was reduced significantly in fistula-operated veins; the relative proportions of high- and low-affinity binding sites did not change. Affinity of high- and low-affinity receptors increased in fistula-operated veins.(ABSTRACT TRUNCATED AT 250 WORDS)
Estrogen pretreatment directly potentiates endothelium-dependent vasorelaxation of porcine coronary arteries
Authors: Bell D. R. , Rensberger H. J. , Koritnik D. R. , Koshy A.
Published: December 2017

We tested whether vasorelaxation of coronary arteries is altered after overnight (18–22 h) exposure to physiological levels of 17 beta-estradiol. Ring segments of left circumflex coronary artery from six female and six castrated male pigs were incubated in vials of sterile Dulbecco's modified Eagle's medium with 1 nM 17 beta-estradiol, 1 nM 17 beta-estradiol + 10 nM tamoxifen, 1 nM 17 alpha-estradiol, or estrogen vehicle (ethanol) under normoxic conditions in an O2-CO2 incubator at 37 degrees C for 18–22 h. Coronary rings, with and without endothelium, were then suspended in vessel baths for measurement of isometric force. Vasorelaxation responses to the calcium ionophore A-23187, ADP, and nitroglycerin were examined in the rings after prostaglandin synthesis blockade and precontraction with U-46619. Sensitivity to A-23187 (-log M concentration required for 50% of maximal relaxation) was significantly enhanced in coronary rings with endothelium from females and castrated males when rings were incubated with 17 beta-estradiol but not when they were incubated with 17 alpha-estradiol or 17 beta-estradiol+tamoxifen. Acute (2h) exposure of coronary arteries to 1 nM 17 beta-estradiol did not alter responses to A-23187. 17 beta-Estradiol (1 nM) was not itself directly vasoactive in coronary arteries with or without prior incubation with the steroid. Vasorelaxation of rings with and without endothelium to ADP and nitroglycerin was not significantly different among the treatment groups. Relaxation to A-23187, but not ADP, was abolished by removal of the endothelium or exposure to 100 microM NO2-L-arginine.(ABSTRACT TRUNCATED AT 250 WORDS)
Effect of SR-49059, a vasopressin V1a antagonist, on human vascular smooth muscle cells
Authors: Serradeil-Le Gal C. , Herbert J. M. , Delisee C. , Schaeffer P. , Raufaste D. , Garcia C. , Dol F. , Marty E. , Maffrand J. P. , Le Fur G.
Published: December 2017

The effects of SR-49059, a new nonpeptide and selective arginine vasopressin (AVP) V1a antagonist, were investigated in binding and functional studies on cultured human aortic vascular smooth muscle cells (VSMC). Characterization of human vascular V1a receptors, using a specific V1a radioiodinated ligand, showed that [125I]-linear AVP antagonist binding to human VSMC membranes was time dependent, reversible, and saturable. A single population of high-affinity binding sites (apparent equilibrium dissociation constant = 15 +/- 6 pM; maximum binding density = 36 +/- 5 fmol/mg protein, i.e., approximately 3,000 sites/cell) with the expected V1a profile was identified. Exposure of these cells to AVP dose-dependently produced cytosolic free [Ca2+] increase [AVP concentration required to obtain a half-maximal response (EC50) = 23 +/- 9 nM] and proliferation (EC50 = 3.2 +/- 0.5 nM). SR-49059 strongly and stereospecifically inhibited [125I]-linear AVP antagonist binding to VSMC V1a receptors [inhibition constant (Ki) = 1.4 +/- 0.3 nM], AVP-evoked Ca2+ increase [concentration of inhibitor required to obtain 50% inhibition of specific binding (IC50) = 0.41 +/- 0.06 nM], and the mitogenic effects induced by 100 nM AVP (IC50 = 0.83 +/- 0.04 nM). OPC-21268, another nonpeptide V1a antagonist, was more than two orders of magnitude less potent than SR-49059 in these models. However, the consistent affinity (Ki = 138 +/- 21 nM) and activity found with OPC-21268 on human VSMC in comparison with the inactivity already observed for other human V1a receptors (liver, platelets, adrenals, and uterus) strongly suggested the existence of human AVP V1a-receptor subtypes.(ABSTRACT TRUNCATED AT 250 WORDS)
Mathematical model that characterizes transmitral and pulmonary venous flow velocity patterns
Authors: Sun Y. , Sjoberg B. J. , Ask P. , Loyd D. , Wranne B.
Published: December 2017

The transmitral and pulmonary venous flow velocity (TMFV and PVFV, respectively) patterns are related to the physiological state of the left heart by use of an electrical analog model. Filling of left ventricle (LV) through the mitral valve is characterized by a quadratic Bernoulli's resistance in series with an inertance. Filling of the left atrium (LA) through the pulmonary veins is represented by a lumped network of linear resistance, capacitance, and inertance. LV and LA are each represented by a time-varying elastance. A volume dependency is incorporated into the LV model to produce physiological pressure-volume loops and Starling curves. The state-space representation of the analog model consists of 10 simultaneous differential equations, which are solved by numerical integration. Model validity is supported by the following. First, the expected effects of aging and decreasing LV compliance on TMFV and PVFV are accurately represented by the model. Second, the model-generated TMFV and PVFV waveforms fit well to pulsed-Doppler recordings in normal and postinfarct patients. It is shown that the TMFV deceleration time is prolonged by the increase in LV compliance and, to a lesser extent, by the increase in LA compliance. A shift from diastolic dominance to systolic dominance in PVFV occurs when LA compliance or pulmonary perfusion pressure increases or when LV compliance or mitral valve area decreases. The present model should serve as a useful theoretical basis for echocardiographic evaluation of LV and LA functions.
Dual regulation of L-type Ca2+ channels by serotonin 2 receptor stimulation in vascular smooth muscle cells
Authors: Hirakawa Y. , Kuga T. , Kobayashi S. , Kanaide H. , Takeshita A.
Published: December 2017

The purpose of the present study was to investigate regulation of voltage-dependent Ca2+ channels by serotonin in rat aortic smooth muscle cells in primary culture. L- and T-type Ca2+ currents (ICa) were recorded using the whole cell voltage-clamp method. Without pretreatment, in 25 of 30 cells examined, 10 microM serotonin decreased L-type ICa to various extents (-14 to -72%). However, in the remaining five cells, serotonin increased L-type ICa 21 +/- 4%. Thus, in 30 cells, serotonin decreased L-type ICa an average of 22 +/- 5%. In the presence of intracellular heparin (100 micrograms/ml), a blocker of inositol 1,4,5-trisphosphate binding to its receptor, serotonin increased L-type ICa in all cells 29 +/- 3% (n = 6). When stored Ca2+ was depleted by pretreatment either with 20 microM ryanodine and 20 mM caffeine or with 100 nM A-23187, serotonin also increased L-type ICa in all cells 30 +/- 5 (n = 4) or 37 +/- 5% (n = 12), respectively. In the presence of heparin, the serotonin-induced increase of L-type ICa was prevented by 100 nM staurosporine (2 +/- 3%; n = 6, P < 0.01). The serotonin-induced decrease of L-type ICa was significantly augmented by 100 nM staurosporine (-43 +/- 10%; n = 5). Phorbol 12,13-dibutylate (PDBu; 1 microM) increased L-type ICa 29 +/- 3% (n = 6), and serotonin did not further increase L-type ICa after its potentiation by PDBu.(ABSTRACT TRUNCATED AT 250 WORDS)
Production of lactic acid and energy metabolism in vascular smooth muscle: effect of dichloroacetate
Authors: Barron J. T. , Parrillo J. E.
Published: December 2017

Vascular smooth muscle metabolism is characterized by substantial production of lactic acid even under fully oxygenated conditions. The role the aerobic production of lactate plays in the energetics of smooth muscle is obscure and was investigated in this study. Helical strips of porcine carotid arteries were incubated in medium containing 1 mM dichloroacetate (DCA), an agent that stimulates pyruvate dehydrogenase and promotes the oxidation of glucose. Lactate production in resting muscle was decreased in the presence of DCA (0.033 +/- 0.006 vs. 0.111 +/- 0.014 mumol.g-1.min-1, P < 0.02), indicating diversion of glucose metabolism from lactate production to enhanced glucose oxidation. This was associated with reduction in the level of ATP+phosphocreatine (PCr) (0.99 +/- 0.01 vs. 1.40 +/- 0.09 mumol/g, P < 0.05) and cataplerosis of the tricarboxylic acid (TCA) cycle. Contraction by KCl was also associated with reduced lactate production in the presence of DCA (0.086 +/- 0.017 vs. 0.20 +/- 0.002 mumol.g-1.min-1, P < 0.01), but ATP+PCr normalized, and there was anaplerosis of the TCA cycle. Glycogen in control arteries declined by approximately 1.3 mumol/g over 30 min K+ contraction but was unchanged in the presence of DCA. By calculation, the glycogen spared could be accounted for by the quantity of glucose diverted from lactate production to glucose oxidation during contraction. It is concluded that the aerobic production of lactate is a mechanism affording optimal coordination and modulation of glucose supply and oxidative energy production with energy demand.
Humoral factor(s) in hypertensive rats trophic for cultured aortic smooth muscle cells
Authors: Overbeck H. W. , Wu G. , Durham J. P.
Published: December 2017

Humoral factors in one-kidney, one-clip (1K,1C) hypertension in rats increase growth of smooth muscle cells cultured from rat arteries. To further characterize the plasma factor or factors involved, we prepared male rats with early, benign 1K,1C hypertension and paired them with one-kidney (1K) normotensive controls. In the presence of growth stimulated by background levels (1%) of fetal calf serum (FCS), plasma-derived serum (PDS), fresh or frozen, from 99 1K,1C rats differentially increased [3H]thymidine incorporation of growth-arrested rat aortic cells; increases were up to 93% more than those evoked by the paired 1K PDS and were concentration related (P < 0.01). However, there was no evidence for a differential effect of 1K,1C PDS in the absence of FCS nor of PDS after boiling. On the other hand, neither treatment of PDS with proteolytic enzymes nor charcoal absorption ablated this differential trophic effect. Thus this study provides evidence that the humoral factor(s) in hypertension are resistant to freezing, proteolysis, and charcoal absorption, but sensitive to boiling, and they require background levels of growth for expression.