Cardiovascular effects of a new inotropic agent, denopamine (TA-064); with reference to it's effects on cardiac hemodynamics and metabolism

A new inotropic agent, denopamine (TA-064) was shown to have a strong positive inotropic effect. Its effect on cardiac hemodynamics and metabolism was evaluated by using wall stress and direct measurement of myocardial oxygen consumption. With plasma concentration of denopamine (21-29 ng/ml on average), attainable by one single oral dose (10 mg), the positive inotropic effect was evident by the significant increase in peak (+)dp/dt (+15% increase from control), and shortening velocity of the left ventricle (+39%), when heart rate or blood pressure was not altered significantly. End diastolic stress and end systolic stress of the left ventricle, defined as indices of preload and afterload, respectively, were reduced significantly. The reduction of preload (-51%) was the result of improved left ventricular filling, and the reduction of afterload (-23%) was due to the increased contractility. Neither coronary sinus blood flow not aortocoronary AV O2 defference was changed. Consequently, myocardial oxygen consumption remained unaltered. When the dose is chosen properly, denopamine is able to exert salutary effects in patients with severe heart failure.

Na+-K+ regulation in cultured vascular smooth muscle cell of the spontaneously hypertensive rat

Na+-K+ passive transport and activity of the Na+ pump were examined in serially passed cultured vascular smooth muscle cells originating from spontaneously hypertensive (SH), Wistar-Kyoto (WKY), and Wistar (W) rats. Measurements included 22Na+ and 86Rb+ (K+ analogue) uptake and washout rate constants as well as intracellular Na+ and K+ levels. The aforementioned variables were studied in cells subjected to either 2 mM Ca2+ or Ca2+-deficient media. In 2 mM Ca2+ medium, SH rat cells demonstrated the highest exchange (uptake and washout) rate constants for Na+ and Rb+ (K+) among cells of the three rat strains. At this extracellular Ca2+ concentration, the Na+ pump activity of SH rat cells was higher than that of WKY rat cells and was not different from that of W rat cells. Incubation in Ca2+-deficient medium resulted in increased magnitudes of Rb+ washout and Na+ uptake rate constants in all cell preparations associated with elevated intracellular Na+ concentrations and augmented activity of the Na+ pump. Under this condition, cells derived from SH rats showed the highest Na+ uptake and Rb+ washout rate constants associated with the highest Na+ pump activity. The increase in intracellular Na+ level in Ca2+-deficient medium was the highest in SH rat cells. These findings show that innate membrane defects and the response of the Na+ pump to these abnormalities can be demonstrated in in vitro-grown vascular smooth muscle cells of the SH rat.

Ouabain binding to cultured vascular smooth muscle cells of the spontaneously hypertensive rat

The binding of ouabain and K+ to the Na+ pump were analyzed in serially passed cultured vascular smooth muscle cells (VSMCs) originating from spontaneously hypertensive (SH), Wistar-Kyoto (WKY), and American Wistar (W) rats. Our techniques have utilized analyses of displacement of [3H]ouabain by both unlabeled ouabain and K+ from specific binding sites on the VSMCs. We have found that each of the VSMC preparations from the three rat strains appeared to demonstrate one population of specific ouabain receptors (Na+ pumps); the number of Na+ pump units (mean +/- SE, expressed as 10(5) units/cell; number of observations indicated in parentheses) of both the SH and WKY rats was significantly lower than the number of Na+ pump units of W rat VSMCs [SH: 3.00 +/- 0.02 (231), WKY: 2.87 +/- 0.05 (245), and W: 3.62 +/- 0.04 (225)]; the equilibrium dissociation constant values (microM) for ouabain in VSMCs of SH and WKY rats were similar but were significantly higher than that of VSMCs derived from W rats [SH: 4.69 +/- 0.09 (231), WKY: 4.57 +/- 0.12 (245), and W: 3.69 +/- 0.17 (225)]; and among the VSMCs originating from the three rat strains, the apparent equilibrium dissociation constant value for K+ (mM) was the lowest in those of the SH rat [1.04 +/- 0.003 (143), compared with VSMCs of the WKY rat [1.54 +/- 0.006 (135)] and W rat [1.19 +/- 0.003 (136)]. Our previous studies have demonstrated increased passive Na+ and K+ transport rate constants of SH rat VSMCs compared with either W or WKY rat cells. These findings suggest the possibility of higher permeabilities of the SH cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Bumetanide-sensitive sodium-22 transport in vascular smooth muscle cell of the spontaneously hypertensive rat

The effect of bumetanide, a known probe of Na+, K+ cotransport, on 22Na+ uptake and washout was examined in serially passed cultured vascular smooth muscle cells of spontaneously hypertensive rats (SHR), Wistar-Kyoto rats (WKY), and Wistar rats. In Ca2+-deficient medium, the drug exerted the greatest effect on 22Na+ washout in vascular smooth muscle cells from SHR and the least effect on cells from WKY. The respective mean values for the apparent bumetanide-sensitive 22Na+ washout rate constants (Ke; X 10(-2)/min) were 7.2, 4.3, and 1.7 for cells from SHR, WKY, and Wistar rats. In both 1 mM Ca2+ and Ca2+-deficient medium, in the presence of 1 mM ouabain, vascular smooth muscle cells from SHR had the highest plateau phase of 22Na+ uptake among the three cell preparations. All cells exhibited higher 22Na+ uptake in Ca2+-deficient medium than in 1 mM Ca2+ medium. Under this condition, bumetanide caused an additional rise in steady state 22Na+ uptake that was most pronounced in cells from SHR (21.3% versus 16.6% for Wistar rats and 4.8% for WKY). This finding indicates that a quantitatively greater inhibition of washout than of the uptake component of the bumetanide-sensitive 22Na+ transport occurs in Ca2+-deficient medium. It is concluded that, in Ca2+-deficient medium, the bumetanide-sensitive 22Na+ washout is higher in vascular smooth muscle cells of SHR than in those of normotensive controls and that this phenomenon reflects a higher Na+ turnover in vascular smooth muscle cell in the hypertensive rat strain.

Histological findings of the right and left ventricular myocardium and clinical follow up in idiopathic ventricular tachycardia

In order to evaluate the etiology of so-called idiopathic ventricular tachycardia, endomyocardial biopsies were performed in four patients with electrocardiographically documented recurrent and sustained ventricular tachycardia. During the episodes of ventricular tachycardia, standard ECG showed a QRS pattern of right bundle branch block with left axis deviation in two patients and left bundle branch block in two patients. The episodes were associated with palpitation, dyspnea and hypotension in all cases. No organic heart disease was detected by physical examination, chest X-ray films, echocardiograms, left ventriculograms or coronary cineangiograms. His bundle electrograms showed blocks at various sites in the atrioventricular conduction system. The biopsy specimens revealed nonspecific myocardial degeneration in the right and left ventricles. These findings suggest mild but wide-spread myocardial damage in both the working myocardium and the conduction system. The clinical course of these patients appeared benign according to follow-up data of one to nine years' duration. None developed overt clinical signs of dilated, hypertrophic or restrictive cardiomyopathy.

Cultured rat vascular smooth muscle cells: extracellular calcium and Na+-K+ regulation

This study explores the relationship between extracellular calcium (Cao) and Na+-K+ regulation as it particularly pertains to the activity of the Na+ pump in cultured vascular smooth muscle cells (VSMCs) originating from Sprague-Dawley rats. As compared with cells incubated in media containing 0.5, 2.0, or 4.0 mM calcium, when the Na pump is active, VSMCs incubated in a Ca-deficient medium show a marked increase in intracellular sodium and no significant change in intracellular potassium. Associated with the rise in intracellular sodium there is an augmented activity of the Na pump. When the Na pump is inhibited, VSMCs incubated in either high-Ca medium (Cao = 4.0 mM) or Ca-deficient medium manifest a greater decline in intracellular potassium than cells incubated in media containing 0.5 or 2.0 mM calcium. Furthermore, when the Na pump is inhibited, VSMCs incubated in a Ca-deficient medium exhibit higher intracellular sodium levels in comparison with their counterparts incubated in media containing calcium. Flux experiments indicate that the aforementioned changes reflect increased membrane permeabilities to Na+ and K+. It is concluded that by regulating the permeability of the VSMC membrane, Cao plays an important role in the intracellular Na+-K+ homeostasis and that its effect on the Na pump is mediated via perturbations in the intracellular Na+ and K+ concentrations.

Increased membrane permeability of skin fibroblasts from the spontaneously hypertensive rat

Recently, we have demonstrated several abnormalities in Na+ and K+ homeostasis in cultured vascular smooth muscle cells derived from spontaneously hypertensive rats (SHR). To study whether similar defects can be identified in other cells of this rat strain, 86Rb and 22Na flux experiments as well as measurements of intracellular Na+ and K+ levels were performed in cultured skin fibroblasts of SHR and normotensive Wistar-Kyoto rats (WKY). The efflux rate constant (ke) for Rb+ (K+ analogue) was higher (p less than 0.001) in fibroblasts of SHR than in those of WKY (2.11 +/- 0.03 and 1.66 +/- 0.02 X 10-2/min; mean +/- SEM). The ouabain-insensitive influx rate constant (ki) for Rb+ was also higher (p less than 0.001) in fibroblasts of SHR than in those of WKY (13.26 +/- 0.41 and 10.71 +/- 0.27 X 10-2/min. On the other hand, the activity of the Na+-K+ pump of cells of SHR (44.81 +/- 0.81 X 10-2/min) was not different from that of cells of WKY (44.72 +/- 0.47 X 10-2/min). This parameter was obtained by calculating the ouabain-sensitive Rb+ influx rate constant. There was also no difference in the Na+ uptake (in the presence of ouabain) between cells of the two rat strains. Although there was no statistically significant difference in the measured intracellular total K+ levels between the two groups, on the basis of equilibrium distribution of 86Rb+, we calculated a significantly lower (p less than 0.001) level of exchangeable intracellular K+ in fibroblasts of SHR (98.2 +/- 1.2 mEq/L) as compared with cells of WKY (115.3 +/- 1.5 mEq/L). These findings indicate increased membrane permeability to K+ in fibroblasts of SHR and that this defect is likely to be innate to their membrane structure.

Factors discriminating survivors and nonsurvivors in alcoholic heart disease

Eighteen patients with dilated cardiomyopathy and a history of excessive ethanol intake were monitored for 3-98 months (mean 23 months). Six patients died (mean age 43.7 +/- 9.2 years) and 12 patients survived (mean age 48.8 +/- 9.5 years). Of the echocardiographic findings taken during heart failure, only the relative wall thickness to the internal dimension of the left ventricle (t/r ratio) differed significantly (survivors 0.33 +/- 0.77 vs. nonsurvivors 0.25 +/- 0.04, P less than 0.05). Of the hemodynamic data obtained after treatment of heart failure, left ventricular end-diastolic pressure differed significantly (survivors 6 +/- 2 vs. nonsurvivors 12 +/- 4 mmHg, P less than 0.001). The two groups could not be differentiated by ejection fraction, cardiac output, end-diastolic or end-systolic volumes, or semi-quantitative analysis of histologic findings obtained by right ventricular endomyocardial biopsy (light microscopy). Only two of six nonsurvivors (33%) succeeded in abstaining from alcohol, while eight of twelve survivors (67%) became teetotalers (P less than 0.05). Total abstinence from alcohol seems to be essential but was not necessarily followed by recovery in the most severe cases. Thus, the absence of adequate hypertrophy and high left ventricular filling pressure may predict the prognosis in alcoholic heart disease.

Electron-microscopic and immunohistochemical studies on endomyocardial biopsies from a patient with eosinophilic endomyocardial disease

Light- and electron-microscopic studies and immunohistochemical procedures were carried out on blood eosinophils and left ventricular endomyocardial biopsies from a 68-year-old man with an eosinophilia of 8.2 X 10(9)/l and congestive cardiac failure due to eosinophilic endomyocardial disease. Some blood eosinophils were vacuolated and degranulated, and reversal of the normal staining pattern of eosinophil granules was seen by means of electron microscopy. The biopsies showed degenerative changes in the cardiac myocytes, with interstitial fibrosis and infiltration by numerous eosinophils, mast cells, and macrophages. Eosinophils infiltrating the myocardium showed a decrease in the number of granules, many of which were indistinct or contained dissolving crystalloids, which occasionally were seen to be discharged onto the surface of adjacent cardiac myocytes. Immunohistochemical studies of the endomyocardial biopsies with a monoclonal antibody, which is specific for activated eosinophils and binds to the secreted forms of eosinophil cationic protein (ECP) and eosinophil protein-X (EP-X), demonstrated that the lesions contained numerous activated eosinophils and secreted ECP and EP-X. These findings support the concept that in eosinophilic endomyocardial disease, activated eosinophils infiltrate and degranulate in the myocardium, releasing eosinophil cationic proteins which then damage adjacent myocardial cells.

The effect of melittin on Na+ and Rb+ transport in cultured skin fibroblasts of the spontaneously hypertensive rat

Melittin effect on transport of Na+ and Rb+(K+ analog) was examined in cultured skin fibroblasts originating from the Spontaneously Hypertensive, Wistar Kyoto and Wistar rats. Melittin increased both Na+ (22Na+) uptake and 86Rb+ efflux as well as the activity of the Na+-pump (ouabain sensitive 86Rb+ uptake) in all three preparations. The effect of the toxin was maximal at a dose of 160-240ng/10(5) cells/ml. At this dose, fibroblasts of the Spontaneously Hypertensive rat demonstrated the greatest response to melittin with respect to the increase in Na+ and Rb+ fluxes and increase in the intracellular Na+ concentrations. It is concluded that melittin can be utilized as a probe to delineate subtle differences in the cellular regulation of Na+ and K+ in the Spontaneously Hypertensive rat as compared with its normotensive controls.

Mechanisms of compensation and decompensation in dilated cardiomyopathy

Left ventricular (LV) function was evaluated in 32 patients with dilated cardiomyopathy (DC) who underwent cardiac catheterization during the past 6 years (group 4), and the results were compared with the data of 30 normal subjects (group 1). The patients were divided into mildly (group 2, 12 patients) and severely symptomatic subgroups (group 3, 20 patients). DC was characterized by dilated and poorly contracting left ventricle with increased muscle mass, reduced cardiac output and elevated systemic vascular resistance. LV volume was larger, ejection fraction was lower, and end-diastolic and end-systolic stresses were higher in group 3 than in groups 1 and 2. No significant differences were seen in LV muscle mass and wall thickness between groups 2 and 3. A significant inverse correlation was seen between ejection fraction and end-systolic stress in patients with DC (Y = -0.05x + 48.7, r = 0.57, p less than 0.01). The slope of the correlation line between end-systolic stress and volume in DC (Y = 1.20x + 135, r = 0.52, p less than 0.02) was less steep than that of normal subjects (Y = 3.68x + 40, r = 0.64, p less than 0.001). These observations indicate that the primary problem of DC is depressed contractility.(ABSTRACT TRUNCATED AT 250 WORDS)

Incidence of the coexistence of left ventricular false tendons and premature ventricular contractions in apparently healthy subjects

The incidence of the coexistence of left ventricular false tendons and premature ventricular contractions (PVCs) was evaluated prospectively. Over 14 months, left ventricular false tendons were found in 71 (6.4%) of 1117 consecutive patients examined echocardiographically. Two types of false tendons were observed: longitudinal, from the ventricular septum to the posteroapical wall (n = 62), and transverse, between the septum and the lateral wall (n = 9). Among 62 patients with PVCs and no underlying heart disease, false tendons were detected in 35 (56%); 28 had unifocal and seven had bifocal PVCs. Episodes of ventricular tachycardia were documented in one of the 28 patients with unifocal PVCs and in one of the seven patients with bifocal PVCs. These PVCs were poorly controlled by antiarrhythmic drugs but easily suppressed by exercise. Left ventricular false tendons were detected in 36 patients on routine echocardiographic examinations performed in the other 1055 subjects, and 10 of these patients were judged to have no underlying heart disease. PVCs were detected in two (20%) of these 10 patients. Although a definite conclusion that left ventricular false tendons are arrhythmogenic cannot be derived from these results, the unexpectedly high incidence of the coexistence suggests that left ventricular false tendons may be an etiologic factor in the development of PVCs, especially the rate-dependent and medically uncontrollable PVCs seen in apparently healthy individuals.

[3H]ouabain binding to cultured rat vascular smooth muscle cells

The number of Na+ pump units (Bmax) and the equilibrium dissociation constant (Kd) for ouabain as well as parameters of K+ binding to the Na+ pump were examined in in vitro-grown vascular smooth muscle cells ( VSMC ) derived from Sprague-Dawley rats. The technique to measure these variables utilizes analyses of [3H]ouabain displacement from its VSMC receptors by nonlabeled ouabain and K+. The mean values for Bmax and Kd in the cultured VSMCs were 1.95 X 10(5) receptor sites per single VSMC and 2.68 X 10(-6) M, respectively. The equilibrium dissociation constant for K+ (Ki) was 0.92 mM. K+ binding to the cultured VSMCs demonstrated positive cooperativity with a Hill coefficient (n) of 1.78.

Cadmium effect on the Na,K-ATPase system in cultured vascular smooth muscle cells

The present study focuses on the interaction between cadmium (Cd) and the Na, K-ATPase system in in vitro grown vascular smooth muscle cells (VSMCs) derived from the rat carotid artery. In disrupted VSMCs rendered permeable by osmotic shock, Cd inhibited Na, K-ATPase; I50 was reached at 10(-5) M Cd. Mg-ATPase was also inhibited by Cd; I50 was attained at concentrations of 10(-4) M Cd. Cd inhibition of Na,K-ATPase in the VSMCs was noncompetitive with respect to Na, K, and ATP. Rubidium transport experiments performed with intact VSMCs demonstrated that within an incubation period of 150 minutes, a concentration of 10(-4) M Cd in the extracellular fluid exerted no acute effect on the Na-K pump. Within this time interval, intracellular Cd attained a concentration eightfold higher than the extracellular Cd concentration. Thus, it appears that under acute conditions Cd exerts its inhibitory effect on Na, K-ATPase only in disrupted VSMCs. The data further suggest that, in the VSMC, conditions under which Cd inhibits Na, K-ATPase are consistent with inhibition from the cytoplasmic side of the cell membrane.

Coxsackie B5 myopericarditis in a young adult--clinical course and endomyocardial biopsy findings

An 18-year-old student with recent gastrointestinal symptoms was found to have Stokes-Adams syndrome. A transvenous pacemaker was successfully inserted with clinical improvement. Subsequent viral titer studies and serum enzyme changes supported the diagnosis of coxsackie B5 myopericarditis. The first cardiac catheterization and endomyocardial biopsy of the right ventricle were performed on the 14th hospital day; the former revealed no hemodynamic abnormalities, but the latter showed marked necrosis of the myofibers, disarray of the remaining ones, mononuclear cell infiltration and the appearance of fibroblasts with fine collagen fiber proliferation in the interstitium. A second biopsy of both ventricles, carried out on the 46th hospital day, showed no necrosis of the myofibers or inflammatory cell infiltration but increasing collagen fiber proliferation in the interstitium and disarray of the surviving myofibers. These pathological findings suggest the healing process of the myopericarditis. To the best of our knowledge, reports of viral myopericarditis with serial endomyocardial biopsies have been few.

Vanadate effect on the Na,K-ATPase and the Na-K pump in in vitro-grown rat vascular smooth muscle cells

The impact of vanadate on the Na,K-ATPase system in the vascular smooth muscle cell is poorly understood. The present study describes the kinetics of the effect of vanadate on Na,K-ATPase and the Na-K pump in in vitro grown rat VSMC's. Vanadate interaction with the Na,K-ATPase system in vascular smooth muscle cells was examined by observing its influence on ouabain-sensitive adenosine triphosphate hydrolysis in disrupted cells rendered permeable by osmotic shock, and the uptake of rubidium by intact cells. The I50 for vanadate inhibition of ouabain-sensitive hydrolysis of adenosine triphosphate occurred at vanadate concentrations of 10(-6) to 10(-7) M. This inhibition was potassium dependent. The maximal inhibitory effect of vanadate occurred at potassium concentrations of 10-20 mEq/liter. Sodium exerted a moderate antagonistic influence on vanadate inhibition of ouabain-sensitive adenosine triphosphate hydrolysis. Rubidium uptake by vascular smooth muscle cells was not altered within 120 minutes when 10(-5) M vanadate was added to the medium containing intact vascular smooth muscle cells. Yet, vanadium concentrations in the vascular smooth muscle cells within this incubation period reached levels 1.48-fold higher than the extracellular vanadate concentrations of 10(-5) M. These observations indicate that vanadate is a potent inhibitor of the VSMC Na,K-ATPase in disrupted vascular smooth muscle cells. However, in intact vascular smooth muscle cells vanadium gaining access into the vascular smooth muscle cell's interior does not inhibit the Na-K pump, probably because of its binding to intracellular proteins and/or conversion from the vanadate to the vanadyl ion.

Cardiovascular effects of a newly synthesized cardiotonic agent (TA-064) on normal and diseased hearts

A new inotropic agent, TA-064, (-)-alpha-(3,4-dimethoxyphenethylaminomethyl)-4-hydroxybenzylalcohol, was shown to have strong effects in experimental animals. Its effectiveness and associated adverse effects were tested in humans invasively (n = 6) and noninvasively (n = 17). Increasing doses of intravenous infusion (1, 2, and 4 micrograms/kg/min) increased plasma levels to 15, 35, and 82 ng/ml, respectively, resulting in marked increases in the peak rate of left ventricular pressure rise (dP/dt) (1,450 +/- 63 to 3,042 +/- 349 mm Hg/s) (mean +/- standard error of the mean [SEM], p less than 0.01) and the ratio of dP/dt to left ventricular pressure at a developed pressure of 40 mm Hg (25 +/- 3 to 39 +/- 2 s-1) (p less than 0.01), with a reduction in left ventricular end-diastolic pressure (12 +/- 2 to 4 +/- 1 mm Hg) (p less than 0.01). Minimal or no changes were seen in heart rate and left ventricular systolic pressure. After a single oral dose (10 mg), the plasma level reached its peak at 90 minutes (16 +/- 9 ng/ml, n = 17). A positive inotropic effect was confirmed echocardiographically in both healthy volunteers (n = 8) and patients with congestive heart failure (CHF) (n = 9) who were maximally treated with conventional regimens: increase in mean velocity of circumferential fiber shortening (healthy volunteers: 1.29 +/- 0.05 to 1.60 +/- 0.11 circ/s [p less than 0.05]; patients with CHF: 0.69 +/- 0.08 to 0.93 +/- 0.09 circ/s [p less than 0.01]), ejection fraction (healthy volunteers: 68 +/- 2 to 75 +/- 2% [p less than 0.05], patients with CHF: 37 +/- 4 to 45 +/- 5% [p less than 0.01]) without change in heart rate. The cardiac index was increased only in the CHF group (2.71 +/- 0.22 to 3.21 +/- 0.24 liters/min/m2) (p less than 0.05). No significant untoward effects were observed. Thus TA-064 is a potent inotropic agent and can be used either parenterally or orally. Salutary effects can be expected in patients with congestive heart failure who are treated with digitalis and diuretic agents.

Hypertrophic nonobstructive cardiomyopathy: a precise assessment of hemodynamic characteristics and clinical implications

A precise assessment of left ventricular function was performed in 20 patients with hypertrophic nonobstructive cardiomyopathy to elucidate the basic pathophysiology, and the data were compared with those in 22 normal subjects. Whereas end-diastolic pressure was high in those with cardiomyopathy, a more accurate index of preload, end-diastolic stress, did not differ from normal value. Afterload was about half the normal value. Both isovolumic indexes [peak positive dP/dt and (dP/dt)/DP40] and ejection phase indexes of contractility (ejection fraction) were in the normal range; however, the end-systolic stress volume ratio was significantly reduced (43% of the normal value). Although the left ventricular minute work index was in the normal range, the unit muscle performance (minute work/mass) was very low (49%). An abnormality of left ventricular relaxation was demonstrated by low peak negative dP/dt (56%) and prolonged time constant T (191%), and a stiff left ventricle was demonstrated by a high diastolic elastic stiffness constant (129%). These observations suggest that the contraction of a unit muscle is inappropriate to produce an adequate contraction of the whole ventricle, and that hypertrophy might be an adaptive process to maintain normal systolic function by increasing mass and reducing afterload.