Biomedical subjects

J B Su

Publications and source records attributed to J B Su.

18 recordsLinked to original sources

PubMed2005

Tumor necrosis factor alpha and glutathione interplay in chronic heart failure.

The pro-inflammatory cytokine, tumor necrosis factor alpha (TNF alpha), in concert with neurohormones, contributes to chronic heart failure (CHF) progression. This implies that TNF a antagonism may constitute an important target for CHF therapy. However, clinical trials in CHF patients using compounds that trap TNF alpha, comprising infliximab, an antibody directed to TNF alpha, and etanercept, a soluble recombinant receptor of TNF alpha, gave disappointing results bringing back to light the dual, short-term beneficial and long-term harmful effect of TNF alpha. This review focuses on the dual, concentration- and time-related effects of TNF alpha, the yin and yang action of TNF alpha in cardiac ischemia/reperfusion and contraction. Importantly, the harmful effects of TNF a are related to glutathione deficiency, a common hallmark to several other chronic inflammatory diseases. Recently, in rat models of CHF, oral administration of the glutathione precursor, N-acetylcysteine (NAC), was shown to hinder pathways of TNF alpha harmful signalling and to rescue cardiac structure and function. These results suggest that glutathione deficiency in association with TNF alpha activation may play a role in the pathophysiology of CHF and that NAC may represent a potential therapy in CHF.

Acetylcysteine↗

PubMed2003

[Aldosterone and its antagonists in heart failure].

THE ROLE OF ALDOSTERONE: Aldosterone is the key hormone in salt-water homeostasis. In heart failure, it participates in the appearance and maintenance of signs of congestion. Predominantly synthesised in the glomerular area of the cortico-adrenal glands, extra adrenal production areas have recently been identified notably in the brain, the heart and the large artery trunks. Aldosterone is activated in the cells by the intracellular mineral corticoid receptor. IN CARDIOVASCULAR-PATHOLOGIES: In chronic heart failure, patients treated with conversion enzyme inhibitor may escape from the renin-angiotensin blockade and this may lead to increased aldosterone plasma levels. This increase can induce not only vascular lesions and myocardial fibrosis but also renal and cerebral lesions. THE EFFECTS OF SPIRONOLACTONE: In patients with NYHA stage III or IV heart failure, addition of spironolactone to the treatment with conversion enzyme inhibitor, diuretic and/or digitalis leads to a reduction in morbidity and mortality, as demonstrated in the RALES study. The mechanisms by which spironolactone has a beneficial effect remain discussed. IN CLINICAL PRACTICE: The prescription of spironolactone is limited by hormonal side effects it provokes. IN THE FUTURE: Eplerenone, a new competitive aldosterone receptor antagonist that appears to be devoid of such side effects and which, at least experimentally may well have the same beneficial effects, is presently under clinical assessment.

Adrenergic beta-Antagonists↗

PubMed2003

[Electromechanical mapping of myocardial ischemia in coronary occlusion in the pig].

The NOGA-Biosense catheter-based mapping technique has been well studied experimentally in infarction model. However, chronic myocardial ischemia with this new device has not been well explored. Thus, the aim of our study was to assess electromechanical changes in a pig aneroid constricor model. To achieved this aim, ten pigs were studied 21 days after the implantation of an aneroid constrictor around the circumflex artery. Coronary reserve assess by intracoronary Doppler flow wire was reduced in the ischemic lateral area (ILA) compared with the nonischemic zone (NIZ) (1.3 +/- 0.1 in the ILA vs. 2.3 +/- 0.2 in the NSZ; p < 0.01). TM echocardiography was used to evaluate myocardial regional contractility under basal condition and after stress induced by rapid atrial pacing. In stress state, the ischemic zone showed an impaired contractility compared with basal state (wall thickening, 32.7 +/- 7.4% vs. 59.7 +/- 8.6%; p < 0.05) whereas the non ischemic zone did not (53.8 +/- 7.6% vs. 60.8 +/- 10.1%; p = ns). Constrast echography showed a decrease in contrast intensity in subendocardium of the ila compared with the niz (46.2 +/- 16.6 vs. 99.2 +/- 35.6; p = 0.03) in pacing. Ventricular mapping quantified unipolar (UV). bipolar (BV) voltage potentials and endocardial local shortening (LLS) in 9 left ventricular regions. In basal state, electrical potentials were preserved in both zones (UV: 9.1 +/- 1.8 mV in the ischemic vs 11.3 +/- 3.6 mV in the non ischemic zone; p = ns; BV: 4.2 +/- 1.1 mV in the ILA vs. 3.9 +/- 1.5 mV; p = ns). In contrast, LLS was significantly lower in the ischemic compared with non ischemic zone (6.4 +/- 5.4% vs. 17.9 +/- 3.0%, p < 0.001). In conclusion, ventricular mapping with the NOGA-Biosense system can identify the ischemic myocardium. In this pig model, the association of a preserved electrical activity and an impaired mechanical activity characterizes the ischemic myocardium. These findings could be interesting in this model in regard of the new developments of the system in particular in the field of angiogenesis.

Animals↗

PubMed2002

[Future molecules in heart failure].

TODAY: The management of heart failure (HF) has considerably progressed over the last two decades. Treatment today relies on prevention and treatment of congestion (limited salt intake, diuretics, converting enzyme inhibitors) and limiting neurohormone stimulation (converting enzyme inhibitors +/- aldactone, beta-blockers). IN THE YEARS TO COME: Based on new concepts, several therapeutic strategies are interesting: blocking over vasoconstrictor systems which have not been taking into account; stimulation of vasodilator and natriuretic systems; modulation of cardiac remodelling; modulation of the immune and inflammatory systems; modification in intrinsic contractility; prevention of rhythm disorders. Among these differing strategies and molecules, it is not easy to predict those that will change the HF prognosis. In any event, their efficacy and safety remain to be demonstrated with large cohort randomised studies. THE PRINCIPLES: To reduce the number of drugs administered, two options appear particularly interesting: measurement of hormone levels (BNP) in order to adjust treatment and administration of molecules with greatest efficacy and safety profiles; limit cardiac remodelling by using new imaging techniques to detect it more precisely and select the molecule(s) exerting the required effect. To target the new molecules better, patients should be classified according to their etiology, stage and progressive profile of their disease, cardiac remodelling, expression of principle endocrine systems and pro-inflammatory cytokines, expression of inflammatory and immune systems and inherent genetic characteristics and response to treatment. This would permit the adaptation of treatment to each individual patient with heart failure.

Forecasting↗

PubMed2002

Inflammation, cytokines and anti-inflammatory therapies in heart failure.

Both experimental and clinical studies have shown a role for inflammation in the pathogenesis of heart failure. This seems related to an imbalance between pro-inflammatory and anti-inflammatory cytokines. Certain categories in patients with dilated cardiomyopathy have shown the presence of humoral and cellular immunity activation suggesting a possible relation between myocarditis and dilated cardiomyopathy. Recent studies suggest a link between the circulating levels of cytokines (TNF alpha IL-1 et IL-6), the clinical status and prognostic. However, the mechanisms connecting heart failure and cytokine activation are unclear and the sites of cytokines production remain controversial. In the clinical setting, specific measurements of cytokines are not available. As tests of inflammation, erythrocyte sedimentation rate and C-reactive protein concentration appear to have interesting pronostic values. Current conventional therapy i.e. ACE inhibitors, type I angiotensin II antagonist and beta-blockers have shown some anti-cytokine properties. Recently, immunosuppressive therapies have shown their ability to improve symptoms and LV ejection in selected patients with dilated cardiomyopathy and clear sign of myocardium inflammation. Specific anti-cytokine therapy have been developed and showed interesting results in preliminary clinical studies. However large clinical trials testing this new therapy have been stoppel prematurely because of deterious effects.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed2000

Stimulation of bradykinin B(1) receptors induces vasodilation in conductance and resistance coronary vessels in conscious dogs: comparison with B(2) receptor stimulation.

BACKGROUND: Constitutive bradykinin B(1) receptors have been identified in dogs; however, their physiological implications involving the coronary circulation remain to be determined. This study examined, in conscious dogs, the coronary response to des-Arg(9)-bradykinin (a B(1) receptor agonist) and the mechanisms involved. METHODS AND RESULTS: Eleven dogs were instrumented with a left ventricular micromanometer, a circumflex coronary catheter, a cuff occluder, a Doppler flow probe, and ultrasonic crystals to measure coronary blood flow velocity (CBFv) and coronary diameter (CD). Intracoronary des-Arg(9)-bradykinin (3 to 100 ng/kg) and bradykinin (0.1 to 10 ng/kg) did not modify systemic hemodynamics but dose-dependently increased CBFv and CD. Des-Arg(9)-bradykinin was less potent than bradykinin. Hoe 140 (a B(2) antagonist, 10 microg/kg) abolished the effects of bradykinin but did not influence the effects of des-Arg(9)-bradykinin. When CBFv increase was prevented by the cuff occluder, CD responses to bradykinin and des-Arg(9)-bradykinin were maintained. Intracoronary lisinopril (0. 75 mg) increased the CD response to bradykinin, with only minimal effect on CBFv, and extended the duration of the effect. Lisinopril did not alter des-Arg(9)-bradykinin responses. Intracoronary N(omega)-nitro-L-arginine (2 mg/kg) decreased the CD effect of bradykinin and prevented the CBFv and CD effects of des-Arg(9)-bradykinin. The relaxing effect of des-Arg(9)-bradykinin on isolated coronary rings was prevented by des-Arg(9), [Leu(8)]-bradykinin. CONCLUSIONS: In the conscious dog, B(1) receptors are present in coronary vessels, and their stimulation produces vasodilation in conductance and resistance vessels, which is mediated essentially by NO but not modulated by angiotensin-converting enzyme. However, the coronary vasodilation induced by B(1) receptor stimulation is not as great as that produced by B(2) receptor stimulation.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1999

Increased bradykinin levels accompany the hemodynamic response to acute inhibition of angiotensin-converting enzyme in dogs with heart failure.

To determine the short-term effects of angiotensin-converting enzyme (ACE) inhibition on hemodynamics and circulating levels of norepinephrine, angiotensin, and bradykinin, responses to enalaprilat and perindoprilat were examined at doses of 0.03, 0.3, and 1 mg/kg in permanently instrumented conscious dogs with pacing-induced heart failure (right ventricular pacing, 240-250 beats/min, 3 weeks). All doses of the two inhibitors produced similar decrease in mean aortic pressure and increase in cardiac output. Neither inhibitor affected plasma norepinephrine level. Both compounds induced a similar 60-80% decrease in blood angiotensin II level, a similar two- to eightfold increase in blood angiotensin I level, and a 80-95% decrease in the angiotensin II/angiotensin I ratio. There were also a fourfold to 10-fold increase in blood bradykinin-(1-9) level, a twofold increase in blood bradykinin-(1-7) level, and a 70-85% decrease in bradykinin-(1-7)/bradykinin-(1-9) ratio. In addition, the changes in total peripheral resistance induced by the two ACE inhibitors were weakly but significantly correlated with the changes in blood angiotensin II or blood bradykinin-(1-9). Thus whatever the specificity of enalaprilat and perindoprilat, both inhibitors produced similar acute hemodynamic effects in dogs with heart failure, which was associated with marked decrease in circulating angiotensin II level and increase in bradykinin-(1-9) level. This study, which measures for the first time in heart failure the blood bradykinin level after ACE inhibitors, indicates, in concert with angiotensin II reduction, a role for increased bradykinin-(1-9) level in mediating short-term hemodynamic effects of ACE inhibition in this model of heart failure.

Angiotensin I↗

PubMed1998

[Effects of high sodium intake on ventricular remodeling in mice].

BACKGROUND: Despite extensive research, controversy still exists regarding the role of dietary sodium intake on hypertension and left ventricular (LV) hypertrophy. Echocardiography is a powerful tool to assess LV hypertrophy and recent technical developments allow now its use in small animals. METHODS: We examined the effect of high sodium intake on LV geometry using echocardiography in mice. Three groups of Swiss mice were submitted, for 8 weeks, to different salt diets (0.6, 2 and 4% NaCl; n = 12, n = 8 and n = 12 respectively). LV end-diastolic (ED) septal and posterior wall thicknesses, LV ED diameter were measured at baseline, 4 and 8 weeks. RESULTS: At baseline, heart rate, LV ED septal and posterior wall thicknesses and LV ED diameter were similar between groups. At 8 weeks, for similar heart rate, LV ED posterior wall thickness were not different (0.6%: 0.64 +/- 0.01, 2%: 0.62 +/- 0.08 and 4%: 0.67 +/- 0.03 mm respectively) but LV septal wall thickness ass increased in a salt diet dependent manner (0.6%: 0.63 +/- 0.01, 2%: 0.75 +/- 0.01, 4%: 0.80 +/- 0.02 mm, p < 0.01). This increase was correlated with urinary sodium excretion (r = 0.84, p < 0.01) but occurred in the absence of change in arterial pressure (tail-cuff plethysmography; 0.6%: 135 +/- 6.2%: 127 +/- 4 and 4%: 139 +/- 9 mmHg respectively). The in-vivo interventricular septal remodeling was confirmed in perfused fixed preparations of hearts. CONCLUSION: Echocardiography allows precise measurements of regional LV wall dimensions in mice, and high sodium intake, in the absence of hypertension, induces interventricular septal remodeling.

Animals↗

PubMed1998

[Physiopathological basis of the treatment of heart failure].

Therapeutic advances have changed the mode of presentation of cardiac failure over the last decades: the main cause, nowadays, is myocardial ischaemia. The modern treatment of cardiac failure is based on relatively simple physiopathological mechanisms which take into account the different aspects of cardiac physiology: a pump, a muscle, a coronary circulation supplying oxygen to the myocardium, an automatic contraction. The concept of vasodilatation and the blocking of vasoconstrictive systems introduced during the 70s is the basis of modern treatment of cardiac failure which involves angiotensin converting enzyme inhibitors and, increasingly, betablockers. In the near future, with earlier treatment of cardiac failure, the stimulation of vasodilator systems could become a new therapeutic strategy. Early detection of ischaemia and its complications with the aim of limiting the loss of cardiac myocytes is a priority for slowing the progression of cardiac failure. The prevention of cardiac failure also depends on educating cardiologists to treat rapidly the factors predisposing to or prolonging episodes of even mild cardiac failure.

Cardiology↗

PubMed1996

Bradykinin pathway is involved in acute hemodynamic effects of enalaprilat in dogs with heart failure.

To determine the role of the renin-angiotensin system and the bradykinin pathway in the mechanism of action of angiotensin-converting enzyme inhibitors in heart failure, the acute effects of enalaprilat (1 mg/kg) were compared with those of a renin inhibitor (ciprokiren, 1 mg/kg i.v.) in 10 chronically instrumented conscious dogs with heart failure induced by right ventricular pacing (3 wk, 240 beats/min). The effects of enalaprilat and ciprokiren on bradykinin infusion (3, 10, and 30 micrograms/min) and the effects of enalaprilat in the presence of the bradykinin B2 receptor antagonist Hoe-140 (10 micrograms/kg i.v.) were also examined. Both inhibitors significantly decreased mean aortic pressure and increased cardiac output. However, enalaprilat induced significantly greater hemodynamic effects than ciprokiren (mean aortic pressure, -13 +/- 3 vs. -6 +/- 1 mmHg; cardiac output, 0.4 +/- 0.1 vs. 0.15 +/- 0.1 l/min). Bradykinin infusion led to dose-dependent decreases in mean aortic pressure and increases in cardiac output that were not modified by pretreatment with ciprokiren but were potentiated 10-fold by enalaprilat. Hoe-140 significantly reduced the hemodynamic effects of enalaprilat. Thus endogenous bradykinin is involved in the acute hemodynamic effects of enalaprilat in experimental heart failure.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1995

Propranolol therapy in experimental heart failure in rabbits improves cardiac response to catecholamines without beta-adrenoceptor up-regulation.

Beta-blockade has been shown to improve cardiac response to catecholamines in heart failure but cellular mechanisms of the improvement are unknown. The effect on left ventricular function of a 14 day propranolol treatment was studied in seven treated and eight non-treated rabbits with experimental heart failure. All animals were subjected to a volume (aortic insufficiency) plus pressure (aortic constriction) overload and were instrumented with a left ventricular catheter and ultrasonic crystals measuring anteroposterior left ventricular diameter. Beta-adrenoceptors were measured using 125I-Cyanopindolol in crude membranes. With isoproterenol, the heart rate was slower in treated rabbits than in non-treated rabbits (p < 0.005) and isoproterenol increased more systolic diameter shortening in treated than in non-treated rabbits (p < 0.05). With norepinephrine, for matched pressures, % delta D increased in the treated group but it did not change in the non-treated group. This improvement of ventricular function was due, in a large part, to an increased diastolic response to norepinephrine: end-diastolic diameter increased in the treated group but not in the non-treated group. In contrast with the improved ventricular response to catecholamines, beta-adrenergic receptor density in the treated group was identical to that of the non-treated group (27.8 fmoles/mg/proteins) and was significantly lower than that of normal rabbits (58.2 fmoles/mg, p < 0.01). The improvement of ventricular response to catecholamines appears to be due to a myocardial protection by propranolol against the toxic effect of catecholamines in heart failure and not, at least in this model, to an up-regulation of beta-adrenoceptors.

Adrenergic alpha-Agonists↗

PubMed1995

Regional alterations of left ventricular contraction and inotropic reserve in conscious dogs with heart failure.

OBJECTIVE: The goal was to examine left ventricular (LV) regional contraction alterations and especially, regional inotropic reserve changes in tachycardia-induced heart failure (HF). METHODS: Eleven dogs were chronically instrumented to measure LV pressure and its first time derivative (LV dP/dt), left atrial and aortic pressures and to measure antero-apical (AS), -basal (BS) and postero-apical (PS) subendocardial segmental contractions by ultrasonic crystals. Dobutamine (5-15 micrograms/kg per min) and left atrial pacing (150-240 beats/min) were performed in the control state (C) and in HF induced by chronic right ventricular pacing (240 beats/min, 3 weeks). RESULTS: In HF, as compared with in C, LV dP/dt max decreased and LV end-diastolic pressure and end-diastolic segmental lengths increased (Ps < 0.005). The percentage of systolic shortening was more depressed in PS (from 21 +/- 1% to 7 +/- 1%, P < 0.001) than in AS and BS (from 24 +/- 1% to 17 +/- 1% and from 20 +/- 2% to 13 +/- 1% respectively, Ps < 0.05). During dobutamine infusion, in HF as compared with C, the increases in LV dP/dt max were smaller (dobutamine 15 micrograms/kg per min: HF: + 36 +/- 6% vs C: + 68 +/- 11%, P < 0.01) and the increases in the systolic shortening of the three segments were also smaller. However, the responses of the three segments were similar in HF and in C. During left atrial pacing, LV dP/dt max increased less in HF than in C and the poststimulation potentiation of LV dP/dt max was impaired in HF. However, the responses of the systolic shortening during regular left atrial pacing and the increase in the percentage of systolic shortening of the first poststimulation beat were similar in all regions. CONCLUSION: In tachycardia-induced HF, although LV regional contraction is heterogeneously altered, the inotropic reserve appears to be similarly modified in all regions.

Analysis of Variance↗

PubMed1992

Limited left ventricular inotropic response to exercise in early phase of pressure overload in dogs.

To study the mechanisms of myocardial adaptation to increased stress in the early phase of left ventricular (LV) pressure overload, 12 dogs were instrumented with LV micromanometer, LV dimensional ultrasonic crystals, aortic catheter, and aortic occluder cuff. After recovery, animals performed graded exercise with acute aortic stenosis (AS) or sustained (24 h) aortic stenosis (SS). At baseline, LV functional parameters with SS were not different from those obtained with AS. LV peak pressure increased similarly during exercise with AS or SS, but LV peak dP/dt was lower with SS than with AS (peak values, 6,292 +/- 525 vs. 7,570 +/- 432 mmHg/s; P < 0.05). LV end-diastolic pressure increased from 9.7 +/- 1.7 to 21.4 +/- 3.3 mmHg (P < 0.05) during exercise with SS, but was unchanged with AS. The decrease of the time constant of isovolumic pressure fall during exercise was significantly smaller after SS than during AS (P < 0.05). In addition, the percentage of subendocardial wall thickening did not increase during exercise with SS (30.3 +/- 3.6%), while it increased significantly with AS (from 29.3 +/- 3.3 to 39.4 +/- 4.5%; P < 0.01). Plasma catecholamine levels were similar at baseline and increased to similar levels during exercise with AS and SS. In the early phase of pressure overload, we conclude that exercise capacity is maintained but that the LV inotropic response to exercise is modified with an altered relaxation process and a lesser utilization of subendocardial inotropic reserve.

Animals↗

PubMed1991

Loading determinants of isovolumic pressure fall in closed-chest dogs.

The respective roles of load level and loading sequence of the left ventricle (LV) are controversial in the in situ heart. They were analyzed under autonomic blockade and sedation in 17 dogs previously instrumented with a pressure micromanometer and ultrasonic crystals measuring LV diameters and wall thickness for computation of LV volume and stress. The time constant of isovolumic pressure fall (T) and end-systolic pressure (ESP) were calculated during the control state, caval occlusion, aortic constriction obtained by inflation of a hydraulic cuff occluder positioned around the aorta, and during the inflation of an intra-aortic balloon. Caval occlusion significantly decreased both ESP (from 124.0 +/- 6.6 to 88.7 +/- 3.7 mmHg; P less than 0.005) and T (from 29.0 +/- 2.2 to 18.8 +/- 2.4 ms; P less than 0.005), which were linearly correlated (mean r = 0.90 +/- 0.03) and inflation of an intra-aortic balloon increased both ESP (from 107.3 +/- 7.1 to 150.6 +/- 10.4 mmHg; P less than 0.005) and T (from 24.6 +/- 2.1 to 32.7 +/- 2.3 ms; P less than 0.005). Both interventions did not modify the loading sequence (analyzed by the evolution of systolic wall stress vs. time). In contrast, aortic constriction delayed to midsystole the time to which wall stress reached its peak and, for matched ESP with intra-aortic balloon inflation, T was not significantly different from control. We conclude that both the level of afterload and the loading sequence of LV are the determinants of T when contractility is not modified.

Animals↗

PubMed1991

Species differences in myocardial beta-adrenergic receptor regulation in response to hyperthyroidism.

The coupling between myocardial beta-adrenergic receptors, adenylate cyclase activity, and the in vivo cardiac response to catecholamines is controversial in hyperthyroidism. The possibility of species differences in beta-adrenoceptor regulation after thyroxine treatment was studied in dogs and in rats. In dogs instrumented with a left ventricular (LV) pressure micromanometer, hyperthyroidism was induced by L-thyroxine (0.5 mg/kg/day i.v. for 10 days). After hyperthyroidism, heart rate was increased to 167 +/- 10 beats/min (control, 107 +/- 8 beats/min; p less than 0.005) with an increase of peak LV dP/dt from 4,243 +/- 471 to 6,105 +/- 862 mm Hg/sec (p less than 0.01). LV response to injection of increasing doses of isoproterenol and dobutamine was not significantly different before and after induction of the hyperthyroid state, as shown by the unchanged slopes of the LV peak dP/dt versus the log of the dose of isoproterenol and dobutamine. Bmax of beta-receptors measured in crude membranes using 3H-CGP 12177 and in homogenates using 125I-cyanopindolol was not increased in hyperthyroid animals as compared with a control group. Basal adenylate cyclase activity was not different in control and hyperthyroid dogs (32 +/- 3 versus 29 +/- 3 pmol/mg/min), and maximal adenylate cyclase activity response to isoproterenol was similar in control and hyperthyroid dogs. In contrast, in rats subjected to hyperthyroidism (0.5 mg/kg/day i.p. L-thyroxine for 10 days), Bmax of adrenoceptors measured using the same methods was significantly increased as compared with control (+72.5% using 3H-CGP 12177 and +41% using 125I-cyanopindolol, but adenylate cyclase activity was not increased in hyperthyroid rats. We conclude that both adenylate cyclase activity and LV response to catecholamines are not increased by thyroxine-induced hyperthyroidism in dogs and that, in contrast with rats, beta-adrenergic density is not increased in hyperthyroid dogs. This indicates a species difference in myocardial beta-adrenoceptor regulation in response to hyperthyroidism.

Adenylyl Cyclases↗

PubMed1991

Increased negative inotropic effect of calcium-channel blockers in hypertrophied and failing rabbit heart.

The effects on ventricular function of calcium channel blockers and isoproterenol were studied in isovolumically beating perfused control rabbit hearts and in hearts subjected to a double pressure plus volume overload studied at the early phase of heart failure. In control hearts, isoproterenol produced an increase of systolic ventricular function and relaxation that was maximal at 10(-7) M. In failing hearts, inotropic state increase in response to isoproterenol was significantly smaller (P less than .01) with no observed lusitropic effect. In control hearts, verapamil and diltiazem produced dose-dependent decreases of ventricular function which were larger with verapamil than with diltiazem (median drug concentration50 of developed pressure was, respectively, 1163 +/- 131 nM and 4524 +/- 451 nM, P less than .001). In failing hearts, contractility decrease was larger than in control hearts (median drug concentration50 of developed pressure was 604 +/- 69 nM and 2691 +/- 580 nM with verapamil and diltiazem, respectively). In contrast, Ro 40-5967, a new calcium-channel blocker, did not produce reductions of inotropic state with concentrations up to 10(-5) M. All three calcium-channel blockers produced a 2-fold increase of coronary flow at 10(-6) M. We conclude that the deleterious effect of verapamil and diltiazem in heart failure is due, at least in part, to a direct depressant effect of these drugs on contractility, which is larger than in control hearts. Additionally, the in vivo sympathetic compensation is probably reduced, as indicated by the decreased ventricular responsiveness to isoproterenol.

Animals↗

PubMed1989

Preload-induced curvilinearity of left ventricular end-systolic pressure-volume relations. Effects on derived indexes in closed-chest dogs.

End-systolic pressure-volume relations (ESPVRs) were analyzed in 10 closed-chest autonomically blocked dogs before and after volume loading that restored end-diastolic volume to its value measured in the control conscious state. Dogs had been previously instrumented with a left ventricular pressure micromanometer and ultrasonic crystals for measurements of major, anteroposterior, and septum-free wall diameters. Left ventricular volume was calculated with an ellipsoidal model in the left ventricular cavity. ESPVRs obtained during caval occlusion after volume loading were curvilinear as shown by the division of the relation into two parts. The initial part of the relation had a significantly smaller ESPVR slope (Ees, 12.0 +/- 1.8 mm Hg/ml) and ESPVR volume-axis intercept (Vd, - 3.5 +/- 0.8 ml) than the final part of the relation (19.5 +/- 3.1 mm Hg/ml and 0.0 +/- 0.6 ml, respectively, p less than 0.01). The end-diastolic volume-peak dP/dt relation showed a similar curvilinearity when end-diastolic volumes were larger than 1.5-1.7 times the minimal end-diastolic volume reached during caval occlusion. ESPVRs were not different during aortic constriction and caval occlusion when end-diastolic volume was small. In contrast, with large end-diastolic volumes, Ees and Vd were significantly smaller during caval occlusion than during aortic constriction. The final part of ESPVR (with small end-diastolic volume) had the same slope and intercept as that during aortic constriction. We conclude that preload produces a curvilinearity of ESPVR that significantly modifies derived indexes when the range of preload changes is large.

Animals↗

PubMedDate not supplied

Preserved vasodilator effect of bradykinin in dogs with heart failure.

BACKGROUND: In heart failure (HF), vasoconstrictor systems are activated and endothelium-derived vasodilation is blunted. Bradykinin, a potent vasodilator, may play an important role in this setting. However, it is not known whether its vasodilator effect is modified in HF. METHODS AND RESULTS: Fourteen chronically instrumented dogs were studied in the control state and in pacing-induced HF (250 bpm for 3 weeks). The dose-dependent decrease in mean aortic pressure (MAP) induced by acetylcholine was significantly blunted in HF. In contrast, in both control and HF, bradykinin infusion caused similar dose-dependent decreases in MAP and increases in cardiac output (CO). This vasodilator effect of exogenous bradykinin was potentiated similarly in both states by enalaprilat, which blocks both angiotensin conversion and bradykinin degradation. For evaluating the role of endogenous bradykinin, the effects of enalaprilat were compared with those of ciprokiren, a pure renin inhibitor. In control, ciprokiren did not produce any effect. Enalaprilat, however, produced a significant decrease in MAP and a significant increase in CO, which were attributed to the inhibition of bradykinin degradation, because these effects were absent after pretreatment with Hoe 140 (a bradykinin B2 receptor antagonist). In contrast, in HF, vasodilator effects of ciprokiren were observed, but enalaprilat produced larger changes in MAP and CO, and after Hoe 140, the hemodynamic effects of enalaprilat were significantly decreased, showing the effects of endogenous bradykinin, which were similar to those measured in control. CONCLUSIONS: In this model of HF with a blunted endothelium-derived vasodilation, the vasodilator effects of exogenous and endogenous bradykinin are preserved. These results suggest that bradykinin may play an important role in HF, in which vasoconstriction is present and endothelium-dependent vasodilation is blunted.

Acetylcholine↗