bluuebunny/crossref_metadata_2025 huggingface dataset:
Arachidonic acid enhances contraction and intracellular Ca2+ transients in individual rat ventricular myocytes
Authors: Damron D. S. , Summers B. A.
Published: December 2017

Modulation of intracellular free Ca2+ concentration ([Ca2+]i) by inotropic stimuli alters contractility in cardiac muscle. Arachidonic acid (AA), a precursor for eicosanoid formation, is released in response to receptor activation and myocardial ischemia and has been demonstrated to alter K+ and Ca2+ channel activity. We investigated the effects of AA on contractility by simultaneously measuring [Ca2+]i and shortening in single field-stimulated rat ventricular myocytes. [Ca2+]i transients were measured using fura 2, and myocyte shortening was assessed using video edge detection. AA stimulated a doubling in the amplitude of the [Ca2+]i transient and a twofold increase in myocyte shortening. In addition, AA stimulated a 30% increase in the time to 50% diastolic [Ca2+]i and a 35% increase in the time to 50% relengthening. These effects of AA were mediated by AA itself (56 +/- 5%) and by cyclooxygenase metabolites. Pretreatment with the protein kinase C inhibitors staurosporine and chelerythrine nearly abolished (> 90% inhibition) these AA-induced effects. Inhibition of voltagegated K+ channels with 4-aminopyridine mimicked the effects of AA. Addition of AA to the 4-aminopyridine-treated myocyte had no additional effect on parameters of contractile function. These data indicate that AA alters the amplitude and duration of Ca2- transients and myocyte shortening via protein kinase C-dependent inhibition of voltage-gated K+ channels. Release of AA by phospholipases in response to receptor activation by endogenous mediators or pathological stimuli may be involved in mediating inotropic responses in cardiac muscle.
Carnosine is a novel peptide modulator of intracellular calcium and contractility in cardiac cells
Authors: Zaloga G. P. , Roberts P. R. , Black K. W. , Lin M. , Zapata-Sudo G. , Sudo R. T. , Nelson T. E.
Published: December 2017

Myocardial contractile failure is a common cause of morbidity and mortality in patients with ischemic heart disease and systemic inflammatory states such as sepsis. Accumulating evidence indicates that contractile failure is associated with dysregulation of myoplasmic calcium levels. In a search for biochemical causes for contractile dysfunction, we found that the dipeptide carnosine improves cardiac contractility and tested the possibility that carnosine plays a role in the regulation of intracellular calcium. Carnosine increased contractility in a dose-dependent manner (1-10 mM) in isolated perfused rat hearts. and it also increased free intracellular calcium levels in isolated myocytes. Carnosine increased myocyte tension via calcium release from the ryanodine receptor calcium release channel in skinned myocardial fibers and increased open-state probability and dwell time of the isolated ryanodine receptor calcium release channel in lipid bilayers. In addition. we report that carnosine sensitizes the contractile proteins so calcium. These results suggest a novel role for carnosine as a modulator of intracellular calcium and contractility in cardiac tissue.
Coordinate regulation of SR Ca(2+)-ATPase and phospholamban expression in developing murine heart
Authors: Harrer J. M. , Haghighi K. , Kim H. W. , Ferguson D. G. , Kranias E. G.
Published: December 2017

Phospholamban, the regulator of Ca(2+)-adenosinetriphosphatase (ATPase) activity in cardiac sarcoplasmic reticulum (SR), is an important determinant of basal myocardial performance. To determine whether phospholamban expression is developmentally regulated in the mouse and whether such regulation reflects alterations in Ca2+ pump activity, hearts from different stages of development were processed for molecular biological and biochemical studies. Both phospholamban and Ca(2+)-ATPase mRNAs were approximately 40% of adult (100%) levels at birth and gradually increased to approach adult levels by day 15 of development. These changes in transcript levels were indicative of changes at the protein level for both phospholamban and Ca(2+)-ATPase. Analysis of the initial rates of Ca2+ uptake demonstrated that over the course of development the upregulation of Ca(2+)-ATPase correlated with increases in the maximal rates of Ca2+ uptake and the constant apparent stoichiometric ratio of phospholamban to Ca(2+)-ATPase correlated with maintenance of a constant affinity of this enzyme for Ca2+ (0.25 +/- 0.03 microM Ca2+). Furthermore, targeted ablation of phospholamban in the mouse resulted in a much higher affinity of Ca2+ uptake for Ca2+ (0.10 +/- 0.02 microM Ca2+) than that observed in wild-type hearts, and this increased affinity was also maintained across different stages of postnatal development. These findings suggest that phospholamban is a major regulator of the affinity of Ca(2+)-ATPase for Ca2+, and coordinate regulation of the expression levels of these two SR proteins may be necessary for maintaining Ca2+ homeostasis in the developing mammalian heart.
Mechanisms of coronary vasoconstriction induced by high arterial oxygen tension
Authors: Mouren S. , Souktani R. , Beaussier M. , Abdenour L. , Arthaud M. , Duvelleroy M. , Vicaut E.
Published: December 2017

In isolated rabbit hearts perfused with suspension of red blood cells, we investigated the role of the endothelium and of several substances in the coronary vasoconstriction induced by a high arterial blood oxygen tension (PaO2). Red blood cells in Krebs-Henseleit buffer were oxygenated to obtain control and high-PaO2 perfusates. Arterial oxygen content was kept constant in both perfusates by reducing hemoglobin concentration in the high-PaO2 perfusate. Coronary blood flow was kept constant so that oxygen supply would not vary with the rise in PaO2. Increases in perfusion pressure therefore reflected increased coronary resistance. The high PaO2-induced coronary vasoconstriction was not affected by administration of indomethacin, nordihydroguaiaretic acid, NG-nitro-L-arginine, or superoxide dismutase and catalase but was abolished after endothelium damage or by cromakalim. These results demonstrate that 1) the endothelium contributes to the high PaO2-induced coronary vasoconstriction; 2) this effect is independent of cyclooxygenase or lipoxygenase products, nitric oxide, or free radicals; and 3) the closure of ATP-sensitive K+ channels mediates this vasoconstriction.
Phospholamban deficiency alters inactivation kinetics of L-type Ca2+ channels in mouse ventricular myocytes
Authors: Masaki H. , Sato Y. , Luo W. , Kranias E. G. , Yatani A.
Published: December 2017

Entry of Ca2+ through voltage-dependent L-type Ca2+ channels is critical for contraction in cardiac cells. In recent studies, cells from phospholamban (PLB) knockout (PLB-KO) mouse hearts showed significantly increased basal contractility with enhanced sarcoplasmic reticulum (SR) Ca2+ uptake. To test whether these effects of PLB ablation were associated with alterations of L-type Ca2+ channel function, we compared the properties of Ca2+ channel currents (I(Ca)) in ventricular myocytes isolated from wild-type (WT) and PLB-KO mouse hearts. L-type Ca2+ channels from mouse myocytes exhibited voltage-dependent gating and sensitivity to dihydropyridine drugs, similar to other mammalian species, and these properties were not altered by PLB ablation. I(Ca) from both WT and PLB-KO cells revealed two (fast and slow) components of inactivation kinetics. However, the proportion of the faster component was significantly larger in PLB-KO cells. Ryanodine (10 microM) reduced the rate of inactivation of I(Ca) for both WT and PLB-KO cells, but the reduction was more prominent in PLB-KO cells compared with WT cells. In contrast, the inactivation in a Ba2+ solution could be fitted by a single exponential similar to the slower component in Ca2+, and this was not altered in PLB-KO cells. The increase in the fast Ca2+-dependent inactivation component in PLB-KO cells supports the hypothesis that Ca2+ released from the SR regulates Ca2+ channel inactivation by affecting the levels of Ca2+ near the channel and suggests that this may be an important compensatory mechanism in the hyperdynamic PLB-KO heart.
Opioid peptide receptor stimulation reverses beta-adrenergic effects in rat heart cells
Authors: Xiao R. P. , Pepe S. , Spurgeon H. A. , Capogrossi M. C. , Lakatta E. G.
Published: December 2017

Opioid peptide receptor (OPR) agonists are co-released with the beta-adrenergic receptor (beta-AR) agonist norepinephrine (NE) from nerve terminals in the heart during sympathetic stimulation. Whereas recent studies indicate that OPR and beta-AR coexist on the surface of cardiac myocytes, whether significant "cross talk" occurs between OPR and beta-AR signaling cascades within heart cells is unknown. In the present study we demonstrate a marked effect of delta-OPR stimulation to modulate beta-adrenergic responses in single isolated rat ventricular myocytes. Nanomolar concentrations (10(-8) M) of the OPR agonist leucine enkephalin (LE), a naturally occurring delta-opioid peptide, inhibited NE-induced increases in sarcolemmal L-type Ca2+ current, cytosolic Ca2+ transient, and contraction. The antiadrenergic effect of LE was pertussis toxin sensitive and abolished by naloxone, an opioid receptor antagonist. In contrast, LE was unable to inhibit the positive inotropic effects induced by equipotent concentrations of 8-(4 chlorophenylthio)-adenosine 3',5'-cyclic monophosphate, a cell-permeant adenosine 3',5'-cyclic monophosphate analog, or by the non-receptor-induced increase in contraction by elevated bathing Ca2+ concentration. These results indicate that an interaction of the OPR and beta-AR systems occurs proximal to activation of the adenosine 3',5'-cyclic monophosphate-dependent protein kinase of the beta-AR intracellular signaling pathway. This modulation of beta-adrenergic effects by OPR activation at the myocyte level may have important implications in the regulation of cardiac Ca2+ metabolism and contractility, particularly during the myocardial response to stress.
Inorganic phosphate as regulator of adenosine formation in isolated guinea pig hearts
Authors: Gorman M. W. , He M. X. , Hall C. S. , Sparks H. V.
Published: December 2017

This study evaluated cytosolic P(i) as an independent regulator of cardiac adenosine formation by dissociating changes in P(i) from changes in AMP and ADP. Myocardial high-energy phosphates (HEP), measured by (31)P nuclear magnetic resonance spectroscopy, were depleted acutely by perfusing isolated guinea pig hearts with 2-deoxyglucose (2-DG), and the effects of 2-DG were compared with a norepinephrine infusion producing similar changes in HEP. 2-DG treatment resulted in lower adenosine release (R(ado)) (54 +/- 18 vs. 622 +/- 199 pmol x min(-1) x g(-1)) and P(i) concentration ([P(i)]) (0.5 +/- 0.1 vs. 6.0 +/- 0.9 mM) than norepinephrine despite similar AMP concentration ([AMP]). Chronic phosphocreatine depletion produced by beta-guanidinopropionic acid feeding also reduced R(ado) and P(i) during hypoxia. Replacement of perfusate glucose and pyruvate with acetate increased R(ado) (from 39 +/- 12 to 356 +/- 100 pmol x min(-1) x g(-1)) and [P(i)] (from 2.0 +/- 0.5 to 5.1 +/- 0.6 mM) with no change in cytosolic [AMP]. Adenosine kinase isolated from guinea pig hearts was inhibited by [P(i)] values seen during hypoxia or hypoperfusion. We conclude that cytosolic [P(i)] can be an important regulator of cardiac adenosine formation through inhibition of adenosine kinase.
Four weeks of cycle training increases basal production of nitric oxide from the forearm
Authors: Kingwell B. A. , Sherrard B. , Jennings G. L. , Dart A. M.
Published: December 2017

The purpose of this study was to determine whether nontrained vascular beds might contribute to the beneficial effects of exercise, including reduced blood pressure by enhanced nitric oxide production. Thirteen healthy, sedentary male volunteers performed 4 wk of normal sedentary activity and 4 wk of cycle training in a randomized order. At the end of each intervention, venous occlusion plethysmography was used to study the forearm blood flow responses to intra-arterial infusions of the nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA), acetylcholine, and sodium nitroprusside. Training increased the maximal work-load and maximal oxygen consumption, whereas intrabrachial blood pressure was reduced. L-NMMA caused a greater vasoconstriction after training (P = 0.004). Net nitrate and nitrite consumption by the forearm was less after training both before and after administration of L-NMMA (P = 0.04), consistent with increased nitrate and nitrite production from nitric oxide metabolism. There was no difference in the response to acetylcholine or sodium nitroprusside between the two states. Preliminary studies showed an increase in forearm blood flow and blood viscosity after cycling, suggesting that elevated shear stress in this vascular bed may contribute to endothelial adaptation and the cardiovascular protective effects of exercise training.
NO increases protein tyrosine phosphatase activity in smooth muscle cells: relationship to antimitogenesis
Authors: Dhaunsi G. S. , Matthews C. , Kaur K. , Hassid A.
Published: December 2017

We investigated the mechanisms of NO-induced antimitogenesis in primary aortic smooth muscle cells from newborn rats. S-nitroso-N-acetylpenicillamine (SNAP), an NO-releasing agent, decreased basal and growth factor-stimulated DNA synthesis with a threshold effectiveness of 0.3-3 microM. A second NO-releasing agent, 3-morpholinosydnonimine-N-ethylcarbamide, a hydrolysis-resistant cyclic nucleotide, 8-bromo-guanosine 3',5'-cyclic monophosphate (8-BrcGMP), and atrial natriuretic peptides elicited a similar effect, whereas 8-bromo-adenosine 3',5'-cyclic monophosphate (8-BrcAMP) was ineffective, supporting the view that NO and cGMP, but not cAMP, mediated at least some of SNAP's antimitogenic effect. SNAP and 8-BrcGMP decreased the levels of phosphotyrosine, especially in proteins of 70-85 kDa and approximately 215 kDa molecular mass. SNAP decreased protein phosphotyrosine levels with a threshold effectiveness similar to that of its antimitogenic effect. Moreover, SNAP increased protein tyrosine phosphatase (PTPase) activity in cell homogenates, indicating that phosphotyrosine dephosphorylation was likely to be the result of increased PTPase activity. Peroxovanadate, a selective PTPase inhibitor, blocked the antimitogenic effect of 8-BrcGMP, suggesting that loss of protein phosphotyrosine and antimitogenesis were causally linked. These findings describe a potential mechanism for NO-induced antimitogenesis in aortic smooth muscle cells in primary culture.
Daily exercise and gender influence postexercise cardiac autonomic responses in hypertensive rats
Authors: Chen Y. , Chandler M. P. , DiCarlo S. E.
Published: December 2017

The influence of daily spontaneous running (DSR) and gender on postexercise cardiac autonomic responses was examined in spontaneously hypertensive rats. Rats were weaned at 4-5 wk of age and were randomly assigned to a sedentary (7 males and 6 females) or DSR (7 males and 8 females) group. After 8 weeks of DSR or sedentary control, rats were chronically instrumented with arterial and venous catheters. After 5 days of recovery, cardiac sympathetic (ST) and parasympathetic tonus (PT) were determined (by the response of heart rate to receptor antagonists) on alternate days under two experimental conditions: no exercise and postexercise. After a single bout of dynamic treadmill exercise (12 m/min, 10% grade for 40 min) ST was reduced (P < 0.05) (male sedentary: no exercise 45 +/- 4 vs. postexercise 28 +/- 3 beats/min; female sedentary: no exercise 69 +/- 10 vs. postexercise 37 +/- 7 beats/ min). PT was also altered after exercise (male sedentary: no exercise -31 +/- 4 vs. postexercise -11 +/- 2 beats/min; female sedentary: no exercise -5 +/- 4 vs. postexercise 7 +/- 4 beats/min). After DSR, ST was reduced (male sedentary 45 +/- 4 vs. DSR 22 +/- 3 beats/min; female sedentary 69 +/- 10 vs. DSR 36 +/- 4 beats/min) (P < 0.05). Finally, male rats had a lower ST and higher PT than female rats. These results demonstrate that 1) ST was reduced after a single bout of dynamic exercise; 2) ST was reduced after DSR; 3) the autonomic response to acute exercise was attenuated after DSR; and 4) there was a gender influence on the cardiac autonomic function.
Properties and modulation of If in newborn versus adult cardiac SA node
Authors: Accili E. A. , Robinson R. B. , DiFrancesco D.
Published: December 2017

The hearts in newborn mammals have greater intrinsic beating rates, rates of diastolic depolarization, and sensitivity to autonomic stimulation than those in adults. The differences could be explained partly by altered properties of the hyperpolarization-activated current (If). To test this possibility, sinoatrial node myocytes from the hearts of newborn (9- to 10-day) and adult (>30-day) rabbits were isolated, and the If was examined with the perforated-patch-clamp technique. The fully activated current-voltage relationship yielded a larger slope conductance of If in newborn SA node myocytes (0.244 +/- 0.020 vs. 0.158 +/- 0.012 pS/pF), compatible with the more rapid diastolic depolarization. Activation curves of the If had similar midactivation voltages (newborn, -66.71 +/- 1.94 mV; adult, -66.33 +/- 2.60 mV), but the slope was significantly greater in newborns (inverse slope factor: newborn, -9.57 +/- 0.35 mV; adult, -11.34 +/- 0.54 mV). No differences in shifts of the If activation curve in response to maximal concentrations of acetylcholine (newborn, -9.70 +/- 1.8 mV; adult, -12.60 +/- 2.10 mV) and isoproterenol (newborn, 6.90 +/- 2.5 mV; adult, 5.3 +/- 1.5 mV) or in the total shift in response to these agonists (newborn, 16.60 +/- 3.30 mV; adult, 18.00 +/- 1.00 mV) were observed. The greater If density and steeper voltage dependence can contribute to both the greater heart rate and the greater sensitivity of the SA node to autonomic modulation in newborn animals.
Macromolecular transport in the arterial intima: comparison of chronic and acute injuries
Authors: Penn M. S. , Rangaswamy S. , Saidel G. M. , Chisolm G. M.
Published: December 2017

Hypertension is a known risk factor for the development of atherosclerosis, which is characterized by the abnormal accumulation of low-density lipoprotein and other plasma-borne macromolecules. The goal of this study was to measure accumulation of a plasma-borne macromolecular marker, horseradish peroxidase (HRP; 44 kDa), in the aortic intima and media of chronically hypertensive rats. HRP transport in 2-yr-old spontaneously hypertensive rats (SHR) was compared with that in age-matched Wistar-Kyoto rats (WKY) under conditions in which blood pressures were not significantly different during the 15-min HRP circulation. Intimal accumulation and medial HRP concentration profiles were obtained from methacrylate-embedded sections after reaction with 3,3'-diaminobenzidine and H2O2. Data were analyzed using a mathematical model of macromolecular transport to quantify the permeabilities of endothelium and internal elastic lamina (IEL). Chronic hypertension increased endothelial permeability without a change in IEL permeability. An apparent convective flux of HRP into the intima of SHR raised intimal HRP to a concentration higher than that of HRP in the plasma. Our results suggest that the intimal accumulation of plasma-borne macromolecules from pressure-driven convection is normally minimized by an intact endothelium. Similar changes resulted from acute injury by lipopolysaccharide, suggesting endothelial injury could account for transport changes associated with hypertension. After either chronic or acute endothelial damage, transport of macromolecules into the intima increases, but the IEL continues to retard transport of macromolecules beyond the intima, resulting in increased intimal accumulation.
Thyroid status and regulation of intracellular sodium in rabbit heart
Authors: Doohan M. M. , Gray D. F. , Hool L. C. , Robinson B. G. , Rasmussen H. H.
Published: December 2017

To examine the effect of thyroid status on the homeostatic control of intracellular Na+, we studied the effect of treatment of hypothyroid rabbits with 3,5,3'-triiodothyronine (T3). Intracellular Na+ and pH (pHi) in papillary muscles and Na+-K+ pump current (Ip) in ventricular myocytes were measured with ion-sensitive microelectrode and whole cell patch-clamp techniques. Na+ influx, estimated from the rate of increase in intracellular Na+ on sudden Na+-K+ pump blockade with dihydroouabain, and Na+ efflux, calculated from Ip, were similar. Treatment with T3 induced an increase in both Na+ influx and Ip. The treatment-induced increase in Na+ influx was eliminated by 5-(N,N-dimethyl)amiloride (DMA) but not by tetrodotoxin. Treatment with T3 increased the rate of fall in pHi on exposure of the papillary muscles to DMA; when the buffer capacity was taken into account, the T3 treatment-induced increase in this rate corresponded well with the treatment-induced, DMA-inhibitable estimate of Na+ uptake. We conclude that thyroid hormone enhances both Na+-H+ exchange-mediated Na+ uptake and Na+-K+ pump-mediated Na+ efflux.
Area postrema-induced inhibition of the exercise pressor reflex
Authors: Bonigut S. , Bonham A. C. , Stebbins C. L.
Published: December 2017

The exercise pressor reflex is opposed by the arterial baroreflex, and circulating peptides may act in the area postrema to enhance this inhibition. Therefore, we tested the hypothesis that the area postrema exerts an inhibitory effect on this reflex. Consequently, in six alpha-chloralose-anesthetized cats, blood pressure and heart rate responses to 30 s of electrically stimulated hindlimb contraction were compared before and after thermal coagulation of the area postrema. In six other cats, the same contraction-induced cardiovascular responses were assessed before and after chemical lesion of the area postrema using kainic acid (214 +/- 9 nl, 2.5-5 mM). Thermal lesion of the area postrema augmented blood pressure and heart rate responses to contraction from 29 +/- 5 to 47 +/- 7 mmHg (P < 0.05) and from 8 +/- 2 to 14 +/- 2 beats/min (P < 0.05), respectively. Chemical lesion of the area postrema enhanced contraction-evoked blood pressure (30 +/- 7 vs. 47 +/- 6 mmHg, P < 0.05) and heart rate (12 +/- 4 vs. 17 +/- 4 beats/min, P < 0.05) responses. These data suggest that the area postrema attenuates the exercise pressor reflex, possibly through the actions of circulating peptides on baroreflex function.
Dietary cholesterol affects Na+-K+ pump function in rabbit cardiac myocytes
Authors: Gray D. F. , Hansen P. S. , Doohan M. M. , Hool L. C. , Rasmussen H. H.
Published: December 2017

Alterations in membrane cholesterol induced in vitro can alter Na+-K+ pump function. Because dietary cholesterol can influence membrane cholesterol in vivo, we examined if dietary cholesterol is a determinant of Na+-K+ pump function. Rabbits were fed cholesterol-supplemented diets for 1-4 wk. Cardiac myocytes were then isolated, and Na+-K+ pump currents (Ip) were measured using the whole cell patch-clamp technique. When the Na+ concentration in the patch pipettes ([Na]pip) was 10 mM, a modest diet-induced increase in serum cholesterol was associated with stimulation of Ip; large increases in serum cholesterol were associated with inhibition. There was no effect of modest or large increases in serum cholesterol on Ip when [Na]pip was 80 mM. The [Na]pip-Ip relationship determined using seven different levels of [Na]pip from 0 to 80 mM indicated that a modest increase in serum cholesterol increased the apparent affinity of the pump for cytoplasmic Na+. In contrast, dietary cholesterol had no effect on the apparent affinity of the pump for extracellular K+. We conclude that cholesterol intake influences the sarcolemmal Na+-K+ pump. This may have clinical implications for cardiovascular function.
Electrode for recording direction of activation, conduction velocity, and monophasic action potential of myocardium
Authors: Horner S. M. , Vespalcova Z. , Lab M. J.
Published: December 2017

Conduction velocity and recovery of excitability are central facets of reentry arrhythmias, and yet there are no satisfactory techniques for the simultaneous measurement of both from the same area of myocardium. We have developed an electrode arrangement that allows the simultaneous recording of conduction velocity, repolarization of the myocardium together with an index of dispersion, and direction of activation of the myocardium. Three silver/silver chloride electrodes were arranged in an equilateral triangle with a reference electrode at the center. From this arrangement three monophasic action potentials were recorded. From the time of arrival of the wavefront of activation at each electrode the direction of activation and conduction velocity were calculated in real time by a computer. There was a good correlation for the in vivo signals from the circular electrode and the new electrode both for conduction velocity (r = 0.99, P < 0.001) and for direction of activation (r = 0.99, P < 0.001). This new mathematical method and electrode design allows the simultaneous measurement of conduction velocity and direction and monophasic action potential, and this can give a beat-by-beat indication of wavelength and dispersion of action potential duration.
Temporal effects of cytokines on neonatal cardiac myocyte Ca2+ transients and adenylate cyclase activity
Authors: Bick R. J. , Liao J. P. , King T. W. , LeMaistre A. , McMillin J. B. , Buja L. M.
Published: December 2017

This study investigates the hypothesis that inflammatory cytokines, interleukin (IL)-1alpha IL-1beta, and tumor necrosis factor (TNF), influence cardiac function by affecting calcium homeostasis and that this effect is mediated by the beta-adrenergic-adenylate cyclase system. After 4 days in culture, neonatal rat ventricular myocytes were treated with cytokines (10 ng/ml) for short (2 h) or longer (18 h) times. Myocyte calcium, contractility, and adenylate cyclase were measured under each condition. Anticipated stepwise increases in adenylate cyclase and intracellular calcium were found in controls (non-cytokine-treated) with 10(-7) M isoproterenol, 10(-7) M isoproterenol + 0.1 mM guanosine triphosphate, and 10(-9) M forskolin. Cells in the presence of cytokine for 2 h show increased basal calcium levels but no changes in adenylate cyclase activities, and isoproterenol fails to elevate adenylate cyclase levels or affect contractile shortening. After long-term treatment with IL-1beta or TNF, but not IL-1alpha, the significantly elevated levels of basal systolic calcium remain, and isoproterenol increases adenylate cyclase activity, unlike after short exposure. Forskolin maximally activates adenylate cyclase following both short- and long-term incubation, but the stepwise increase in activity is blunted following prolonged exposure. Thus short-term cytokine treatment blocks the adrenergic receptor-mediated increases in adenosine 3',5'-cyclic monophosphate, dissociating adenylate cyclase activation from cytokine-mediated increases in cell calcium, whereas longer treatment apparently produces direct affects on adenylate cyclase. Time-dependent differences in contractile response were found with IL-1alpha at 2 h and TNF at 18 h, implying that myofibrillar responsiveness to increased cytoplasmic calcium is dependent on both cytokine species and exposure time.
Estrogen reduces proliferation and agonist-induced calcium increase in coronary artery smooth muscle cells
Authors: Bhalla R. C. , Toth K. F. , Bhatty R. A. , Thompson L. P. , Sharma R. V.
Published: December 2017

Epidemiological evidence and estrogen replacement studies suggest that estrogen has a protective effect on the cardiovascular system against coronary artery disease. Vascular smooth muscle (VSM) cell replication has been shown to play a causative role in the pathogenesis of atherosclerosis. Therefore, in this study, we investigated the effect of chronic treatment of cultured guinea pig coronary artery VSM cells with physiological concentrations of 17beta-estradiol (E2) on thymidine incorporation, cell proliferation, and bradykinin-stimulated cytosolic calcium concentration ([Ca2+]i). Bradykinin at physiological concentrations causes contraction of endothelium-denuded guinea pig coronary artery rings in a concentration-dependent manner. VSM cells were first treated with low doses of E2 (10 pg/ml) for 1-2 days followed by treatment for 4-6 days with 50 pg/ml of E2, a concentration similar to that found in pregnancy. Using these protocols, we consistently observed the presence of E2-receptor mRNA in VSM cells by a ribonuclease protection assay. Fetal calf serum-stimulated [3H]thymidine incorporation was significantly reduced (P < 0.05) in E2-treated cells compared with untreated control cells. Similarly, E2 treatment significantly inhibited fetal calf serum-stimulated VSM cell proliferation compared with untreated control cells (P < 0.05). We also tested the hypothesis that E2 treatment attenuates agonist-stimulated [Ca2+]i in VSM cells because acute E2 treatment has been shown to produce relaxation of precontracted isolated coronary artery preparations. E2 treatment of VSM cells resulted in a significant decrease in bradykinin-stimulated [Ca2+]i compared with untreated cells (P < 0.05). In conclusion, our data demonstrate that estrogen at physiological concentrations directly regulates coronary VSM cell function.
Influence of hypoxia on endothelin-1 binding sites in neonatal porcine pulmonary vasculature
Authors: Noguchi Yasuzo , Hislop Alison A. , Haworth Sheila G.
Published: December 2017

Pages H669–H678: Yasuzo Noguchi, Alison A. Hislop, and Sheila G. Haworth. “Influence of hypoxia on endothelin-1 binding sites in neonatal porcine pulmonary vasculature.” On page H671, Fig. 1 should appear as below (part of the x-axis in A was inadvertently masked by B).

(See PDF)
Oxidants increase intracellular free Zn2+ concentration in rabbit ventricular myocytes
Authors: Turan B. , Fliss H. , Desilets M.
Published: December 2017

Oxidative stress may alter cardiac function by affecting intracellular free Zn2+ concentrations ([Zn2+]i). Rabbit ventricular myocytes loaded with fura 2 were used to fluorometrically measure resting [Zn2+]i (0.23 +/- 0.03 nM) and intracellular Ca2+ concentration ([Ca2+]i) (36 +/- 7 nM). Fluorescence quenching by the heavy metal chelator N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine was used to quantitate [Zn2+]i. The thiol-reactive oxidants hypochlorous acid (0.1 mM) and selenite (1 mM) increased [Zn2+]i to 7.7 +/- 1.7 and 6.1 +/- 1.7 nM, respectively, within 5 min. Dithiothreitol (0.5 mM), a disulfide-reducing agent, rapidly restored normal [Zn2+]i. The oxidants did not affect [Ca2+]i. However, depolarization-induced Ca2+ transients and Ca2+ currents were zinc dependent. [Zn2+]i-associated fluorescence was substantial and, if ignored, it led to overestimation of [Ca2+]i by approximately twofold before oxidant treatment and by approximately eightfold after oxidants. The results demonstrate that [Zn2+]i 1) can be greatly increased by thiol-reactive oxidants; 2) may contribute to oxidant-induced alterations of excitation-contraction coupling; and 3) has strong fura 2 fluorescence which, if overlooked, can lead to significant overestimation of [Ca2+]i.
Cardiac autonomic control is inversely related to blood pressure variability responses to psychological challenge
Authors: Sloan R. P. , Demeersman R. E. , Shapiro P. A. , Bagiella E. , Kuhl J. P. , Zion A. S. , Paik M. , Myers M. M.
Published: December 2017

Blood pressure exhibits variability (BPV) at low (0.02- to 0.07-Hz), mid (0.07- to 0.15-Hz)-, and high (0.15- to 0.50-Hz) frequencies. Evidence suggests that BPV responses to challenge are inversely related to cardiac autonomic control. We tested this hypothesis by examining the BPV responses to psychological stressors in 22 normal subjects who differed in cardiac control, operationalized as resting heart period variability (HPV). HPV and BPV were measured noninvasively or a beat-to-beat basis. The stressors produced a significant increase in heart rate and a small but significant increase in diastolic blood pressure. As predicted, the changes in BPV in response to the stressors were inversely related to resting HPV. The results are interpreted in terms of a model of cardiovascular control that holds that BPV originates from feedforward effects of central control of the heart, feedback effects mediated through the baroreflexes, and direct sympathetic vascular effects.
Pulmonary distribution of iodoantipyrine: temperature and lipid solubility effects
Authors: Chinard F. P. , Basset G. , Cua W. O. , Saumon G. , Bouchonnet F. , Garrick R. A. , Bower V.
Published: December 2017

In multiple indicator-dilution studies in rat and dog lungs, we have found that the distribution of iodoantipyrine (IAP) is not limited by the endothelium at a temperature > 7 degrees C but is barrier limited at the epithelium at a temperature < 15 degrees C (permeability coefficient of 6.3 x 10(-5) cm/s at 8 degrees C). IAP extraction from the vascular surface to the tissues is greater than those of antipyrine (AP) and tritiated water (THO). IAP transmittance from the alveolar surface to the vascular compartment is smaller than those of AP and THO: a lung lipid compartment, probably in the lamellar bodies of the type II cells, is more accessible to IAP than to AP or THO because IAP has a higher oil-to-water distribution coefficient. Our mathematical model takes into account these matters and also the low surface density of the type II cells: some of the IAP may bypass the lipid compartment. Lipid may affect the transit of solutes with high oil-to-water distribution coefficients in the lungs and across the alveolar-capillary barrier.
Estrogen replacement attenuates resistance artery adrenergic sensitivity via endothelial vasodilators
Authors: Meyer M. C. , Cummings K. , Osol G.
Published: December 2017

The objective of this study was to determine whether chronic estrogen replacement alters adrenergic constriction and endothelium-dependent dilation in resistance arteries from the rat. Resistance-sized (< 200 microns) mesenteric arteries from castrated female Sprague-Dawley rats with (E2; 21 day, 0.5-mg pellet) and without (OvX) estrogen replacement were removed for in vitro study on a pressurized arteriograph system. Sensitivity to alpha-adrenergic constriction and the role of the endothelium in its modulation and of agonist-provoked endothelium-dependent relaxation were determined. Estrogen-treated rats had decreased heart rate as well as systolic and diastolic blood pressure. Arteries from estrogen-replaced rats were fivefold less sensitive to alpha 1-adrenergic stimulation with phenylephrine (50% effective concentration: E2, 3.2 +/- 1.1 microM; OvX, 0.6 +/- 0.2 microM; P < 0.05). This difference was abolished by endothelial denudation, blockade of cyclooxygenase (1 microM ibuprofen), or nitric oxide synthase blockade (0.24 mM N omega-nitro-L-arginine). There was no difference in muscarinic agonist-provoked relaxation or vascular smooth muscle sensitivity to prostacyclin or sodium nitroprusside. These results indicate that estrogen replacement decreases resistance artery adrenergic sensitivity by increasing the basal release of relaxing factors from the endothelium. This effect on small artery function may produce dual cardioprotective effects by decreasing peripheral resistance, blood pressure, and the likelihood of thrombosis.
Physiological assessment of complex cardiac phenotypes in genetically engineered mice
Authors: Christensen G. , Wang Y. , Chien K. R.
Published: December 2017

The recent development of techniques for surgical manipulation and for the assessment of cardiac physiology in genetically engineered mice has allowed scientists to address some of the most fundamental questions related to congenital and acquired forms of human heart disease. This review discusses recent advances in the techniques for studying cardiac disease using the mouse as a model system. Because cardiac overload is one of the most important stimuli for development of hypertrophy and heart failure in humans, various models of cardiac pressure and volume overload, as well as myocardial ischemia, have been developed and characterized. Moreover, it is possible to reliably examine murine cardiac physiology in vivo with microtransducers, echocardiography, and other miniaturized techniques. Sophisticated methods have also been developed to enable an examination of single-cell phenotypes of isolated cardiomyocytes derived from genetically engineered mice. These physiological assessments, coupled with conventional histology and molecular markers, have allowed the characterization of several gene-targeted and transgenic mouse models of hypertrophy and dilated cardiomyopathy, as well as mouse models of cardiac developmental defects. Such mouse models of heart disease will ultimately allow the molecular dissection of the interplay between the various factors leading to heart disease, and they may serve as a guide to appropriate therapeutic strategies for human heart disease.
Lysophosphatidylcholine stimulates leukocyte rolling and adherence in rat mesenteric microvasculature
Authors: Scalia R. , Murohara T. , Campbell B. , Kaji A. , Lefer A. M.
Published: December 2017

Synthetic exogenous lysophosphatidylcholine (LPC) was used to induce leukocyte-endothelial cell interaction, utilizing intravital microscopy in the rat mesenteric microvasculature. Superfusion of the rat mesentery with 10 microM LPC significantly and time dependently increased leukocyte rolling and adherence compared with control rats. Moreover, LPC superfusion did not alter systemic blood pressure or mesenteric venular shear rate. Administration of either an anti-P-selectin monoclonal antibody (PB1.3 at 1 mg/kg i.v.) or a nitric oxide (NO) donor (CAS-1609, 10 microM superfusion) markedly attenuated LPC-induced leukocyte rolling and adherence (P < 0.01 from LPC alone). Immunohistochemical localization of P-selectin and intercellular adhesion molecule-1 (ICAM-1) expression on mesenteric venules was significantly increased after exposure to LPC compared with mesenteries superfused with phosphatidylcholine (P < 0.001). Flow cytometric analysis indicated that 10 microM LPC significantly (P < 0.05) increased P-selectin fluorescence on rat platelets. Furthermore, direct measurement of NO release from rat aortic vascular endothelium was significantly (P < 0.05) inhibited by 10 microM LPC. Thus LPC induces in vivo leukocyte rolling and adherence in the mesenteric rat microvasculature by increasing the surface expression of P-selectin and ICAM-1. Because inhibition of endothelial NO release promotes P-selectin expression, LPC-induced rolling and adherence may be mediated via reduced NO release.
Cytosolic [Ca2+], [Na+], and pH in guinea pig ventricular myocytes exposed to anoxia and reoxygenation
Authors: Ralenkotter L. , Dales C. , Delcamp T. J. , Hadley R. W.
Published: December 2017

The aim of this study was to evaluate whether the magnitude and time course of the intracellular acidification observed in anoxic cardiac myocytes was sufficient to protect against reoxygenation-induced hypercontracture. Cytosolic [Ca2+], [Na+], and pH were measured using fluorescent indicators in myocytes that were first subjected to both anoxia and glucose deprivation and then oxygen and glucose restoration 15-30 min after the onset of rigor. The cytosol underwent a profound acidification early in anoxia (pH 7.21 to 6.84) that reached a plateau at the time of rigor contracture. In contrast, [Na+] rose throughout anoxia. Cytosolic [Ca2+] underwent little rise during anoxia, but reoxygenation induced a large spike in [Ca2+]. Reoxygenation also induced a significant secondary acidification of the cytosol that was apparently induced by the spike in [Ca2+]. The characteristics of this secondary acidification were deemed sufficient to provide partial protection against the hypercontracture associated with the reoxygenation-induced [Ca2+] transient.
Nitric oxide inhibits neutrophil adhesion to cytokine-activated cardiac myocytes
Authors: Ohashi Y. , Kawashima S. , Hirata K. , Akita H. , Yokoyama M.
Published: December 2017

Neutrophils play important roles in myocardial injury in which an inflammatory reaction ensues. We investigated the role of nitric oxide (NO) in neutrophil adhesion to cardiac myocytes. Isolated adult rat myocytes were coincubated with human neutrophils, and the number of neutrophils adherent to myocytes was microscopically counted. The adhesion increased up to 2.4-fold when both myocytes and neutrophils were activated by interleukin-1 beta (IL-1 beta) and platelet-activating factor (PAF), respectively. The NO donors, S-nitroso-N-acetylpenicillamine (SNAP) and sodium nitroprusside (SNP), inhibited the adhesion by 50% when administered to neutrophils before activation. However, when activated neutrophils were added to myocytes that had been incubated with NO donors during IL-1 beta stimulation, the inhibition of adhesion was not observed. Pretreatment of neutrophils with SNAP or 8-bromoguanosine 3',5'-cyclic monophosphate did not reduce PAF-induced CD11b/CD18 expression determined by flow cytometry, nor did simultaneous treatment of myocytes with IL-1 beta and SNAP decrease IL-1 beta-induced intercellular adhesion molecule-1 expression determined by immunofluorescence staining and enzyme-linked immunosorbent assay. Thus NO inhibits neutrophil-myocyte adhesion, mainly acting on neutrophils without quantitatively affecting the upregulation of CD11b/CD18.
Uncoupling of local cerebral glucose metabolism and blood flow after acute fluid-percussion injury in rats
Authors: Ginsberg M. D. , Zhao W. , Alonso O. F. , Loor-Estades J. Y. , Dietrich W. D. , Busto R.
Published: December 2017

We assessed local cerebral glucose metabolism (lCMRGlc) and blood flow (lCBF) interrelationships in the first hour after parasagittal fluid-percussion head injury (FPI) in rats. Matched series were studied autoradiographically for lCMRGlc and lCBF with 2-[14C]deoxyglucose and 14C-labeled iodoantipyrine, respectively. Three-dimensional autoradiographic-image mapping was to generate average data sets from which a mean ICMRGlc-to-lCBF ratio data set was derived. lCBF in neocortical regions ipsilateral to the trauma were depressed, on average, by 44% compared with sham-FPI rats, whereas contralateral lCBF values were not altered. By contrast, ICMRGlc was elevated in many cortical and subcortical sites of both hemispheres; this amounted to 1.3- to 1.4-fold increases in neocortical regions in the thalamus and 1.6- to 1.7-fold increases in the hippocampus. The lCMRGlc-to-lCBF ratio data revealed striking elevations both ipsilateral (P = 7 x 10(-7) and contralateral to the FPI (P = 0.003). The extent of metabolism-flow uncoupling, on average, amounted to 2.5-fold in the ipsilateral hippocampus and neocortex and 1.7-fold contralaterally. The loci of pronounced metabolism-flow dissociation corresponded closely to the previously documented histological distribution of neuronal necrosis. Our findings resemble events occurring in the acute focal ischemic penumbra and suggest that similar injury mechanisms may be operative.
Effects of hibernation on neural and endothelial control of mesenteric arteries of the golden hamster
Authors: Ralevic V. , Hill B. , Crowe R. , Knight G. , Burnstock G.
Published: December 2017

The effects of hibernation on mesenteric arterial innervation and function were examined using pharmacological and immunohistochemical techniques in age-matched controls, cold-exposed controls, and 4-wk-hibernated golden hamsters. Electrical field stimulation of the isolated mesenteric arterial bed elicited frequency-dependent vasoconstriction. The sensitivity of responses was significantly increased in tissues from hibernating animals compared with cold-exposed controls. Vasoconstrictor responses to exogenous norepinephrine were also increased in hibernation. However, there was a significant decrease in sensitivity of vasoconstriction to ATP in hibernated and cold-exposed tissue compared with age-matched controls. In preparations preconstricted with methoxamine, endothelium-dependent vasodilator responses to acetylcholine and ATP were similar among the groups. Immunohistochemical investigation of mesenteric arteries revealed no differences among the groups in density of innervation by nerves immunoreactive for tyrosine hydroxylase, neuropeptide Y, and calcitonin gene-related peptide. Postjunctional changes appear to occur in hibernation, leading to augmentation of sympathetic vasoconstriction, which is consistent with the increase in peripheral vascular resistance in hibernation. Endothelium-dependent vasodilatation is not significantly changed in hibernation in the hamster mesenteric arterial bed.
Cytoskeletal rearrangement mediates human microvascular endothelial tight junction modulation by cytokines
Authors: Blum M. S. , Toninelli E. , Anderson J. M. , Balda M. S. , Zhou J. , O'Donnell L. , Pardi R. , Bender J. R.
Published: December 2017

The tight junction (TJ) is a specialized intercellular structure responsible for the regulation of ionic and macromolecular flux across cell monolayers. Because plasma leakage is believed to occur mainly across the microvasculature, we hypothesized that microvascular endothelial cells (MVEC) may form more intact, regulatable TJ than other endothelial cell (EC) types, allowing further insight into the control of EC permeability. Primary cultures of MVEC monolayers produced transmonolayer electrical resistances (TER) of 120-155 omega.cm2, approximately 10 times that of large-vessel EC. Treatment with tumor necrosis factor and interferon-gamma caused a 50% decrease in the TER and a striking fragmentation of the basal, continuous interendothelial cell zonula occludens-1 protein (ZO-1) distribution determined by immunofluorescence. Fragmentation was inhibited by cytochalasin D, and confocal microscopy demonstrated a colocalization between F actin and ZO-1. These findings suggest that the F actin cytoskeleton plays a central role in endothelial TJ barrier regulation and that dynamic cytoskeletal alterations may primarily control vascular permeability.