Abstract-To determine the effects of aging on vasoactivity in a primate model (Macaca fascicularis), 13 young male monkeys (aged 7.1Ϯ0.4 years) and 9 old male monkeys (aged 19.8Ϯ0.6 years) were chronically instrumented for measurement of left ventricular and aortic pressures and cardiac output. Total cholesterol, triglyceride, and fasting blood sugar levels were not different between the 2 groups. There were no significant differences in baseline mean aortic pressure and total peripheral resistance (TPR) in the young monkeys versus the old monkeys. TPR fell less (PϽ0.05) with acetylcholine (1 g/kg) in old monkeys (Ϫ25Ϯ1%) than in young monkeys (Ϫ34Ϯ2%), whereas decreases in TPR with sodium nitroprusside were similar in old and young monkeys. There was no evidence of atherosclerosis, but apoptosis of endothelial cells was enhanced (PϽ0.05) in the aortas and femoral arteries, but not in the media, of the old monkeys. There was a relationship (rϭ0.62, Pϭ0.013) between the incidence of terminal deoxynucleotidyl transferasemediated dUTP nick end-labeling (TUNEL)-positive endothelial cells and endothelial cell density in the femoral artery. The reduced endothelial cell density was also correlated (rϭ0.82, PϽ0.01) with depressed TPR responses to acetylcholine. Thus, vascular endothelial dysfunction was present in old monkeys without evidence of atherosclerosis, which may be due to endothelial apoptosis and reduced endothelial cell density. (Arterioscler Thromb Vasc Biol.

By subtractive hybridization, we found a significant increase in H11 kinase transcript in large mammalian models of both ischemia/reperfusion (stunning) and chronic pressure overload with hypertrophy. Because this gene has not been characterized in the heart, the goal of the present study was to determine the function of H11 kinase in cardiac tissue, both in vitro and in vivo. In isolated neonatal rat cardiac myocytes, adenoviral-mediated overexpression of H11 kinase resulted in a 37% increase in protein/DNA ratio, reflecting hypertrophy. A cardiac-specific transgene driven by the alphaMHC-promoter was generated, which resulted in an average 7-fold increase in H11 kinase protein expression. Transgenic hearts were characterized by a 30% increase of the heart weight/body weight ratio, by the reexpression of a fetal gene program, and by concentric hypertrophy with preserved contractile function at echocardiography. This phenotype was accompanied by a dose-dependent activation of Akt/PKB and p70(S6) kinase, whereas the MAP kinase pathway was unaffected. Thus, H11 kinase represents a novel mediator of cardiac cell growth and hypertrophy.

To study the physiological effect of the overexpression of myocardial Gsalpha (protein levels increased by approximately threefold in transgenic mice), we examined the responsiveness to sympathomimetic amines by echocardiography (9 MHz) in five transgenic mice and five control mice (both 10.3 +/- 0.2 months old). Myocardial contractility in transgenic mice, as assessed by left ventricular (LV) fractional shortening (LVFS) and LV ejection fraction (LVEF) was not different from that of control mice at baseline (LVFS, 40 +/- 3% versus 36 +/- 2%; LVEF, 78 +/- 3% versus 74 +/- 3%). LVFS and LVEF values in transgenic mice during isoproterenol (ISO, 0.02 micrograms/kg per minute) infusion were higher than the values in control mice (LVFS, 68 +/- 4% versus 48 +/- 3%; LVEF, 96 +/- 1% versus 86 +/- 3%; P < .05). Norepinephrine (NE, 0.2 micrograms/kg per minute) infusion also increased LVFS and LVEF in transgenic mice more than in control mice (LVFS, 59 +/- 4% versus 47 +/- 3%; LVEF, 93 +/- 2% versus 85 +/- 3%; P < .05). Heart rates of transgenic mice were higher than those of control mice during ISO and NE infusion. In three transgenic mice with heart rates held constant, LV dP/dt rose by 33 +/- 2% with ISO (0.02 micrograms/kg per minute) and by only 13 +/- 2% in three wild-type control mice (P < .01). NE (0.1 micrograms/kg per minute) also induced a greater effect on LV dP/dt in the three transgenic mice with heart rates held constant compared with three wild-type control mice (65 +/ 8% versus 28 +/- 4%, P < .05). Pathological and histological analyses of older transgenic mouse hearts (16.0 +/- 0.8 months old) revealed hypertrophy, degeneration, atrophy of cells, and replacement fibrosis reflected by significant increases in collagen volume in the subendocardium (5.2 +/- 1.4% versus 1.2 +/- 0.3%, P < .05) and in the cross-sectional area of myocytes (298 +/- 29 versus 187 +/- 12 micron2, P < .05) compared with control mouse hearts. These results suggest that Gsalpha overexpression enhances the efficacy of the beta-adrenergic receptor-Gs-adenylyl cyclase signaling pathway. This in turn leads to augmented inotropic and chronotropic responses to endogenous sympathetic stimulation. This action over the life of the animal results in myocardial damage characterized by cellular degeneration, necrosis, and replacement fibrosis, with the remaining cells undergoing compensatory hypertrophy. As a model, this transgenic mouse offers new insights into the mechanisms of cardiomyopathy and heart failure and provides a new tool for their study.

Calculating changes in plasma lactate concentration following initial treatment in dogs with GDV may assist in determining prognosis and identifying patients that require more aggressive treatment.

The goal of this study was to determine whether chronic endogenous sympathetic stimulation resulting from the overexpression of cardiac stimulatory G protein alpha subunit (Gs alpha) in transgenic mice (15.3 +/- 0.1 mo old) resulted in a clinical picture of cardiomyopathy. The left ventricular ejection fraction, measured by echocardiography, was reduced in older mice with Gs alpha overexpression (50.4 +/- 5.4%) compared with age-matched control mice (70.9 +/- 1.6%; P < 0.05). When ejection fractions were compared at similar heart rates, the Gs alpha mice exhibited a greater left ventricular end-diastolic dimension than control mice (4.3 +/- 0.2 vs. 3.7 +/- 0.1 mm; P < 0.05). Baseline heart rates were elevated in conscious Gs alpha mice (722 +/- 27 beats/min; n = 5) compared with control mice (656 +/- 28 beats/min; n = 5). Moreover, electrocardiographic monitoring demonstrated a high incidence of arrhythmias. Increased mortality compared with control mice (31.6 vs. 3.0%; P < 0.01) was also observed. Thus older mice with Gs alpha overexpression exhibit many of the features of dilated cardiomyopathy. This study supports the concept that chronic sympathetic stimulation over an extended period of time, i.e., over the life of an animal, is deleterious and actually may result in cardiomyopathy.

No abstract

Therapy for ischemic heart disease has been directed traditionally at limiting cell necrosis. We determined by genome profiling whether ischemic myocardium can trigger a genetic program promoting cardiac cell survival, which would be a novel and potentially equally important mechanism of salvage. Although cardiac genomics is usually performed in rodents, we used a swine model of ischemia͞reperfusion followed by ventricular dysfunction (stunning), which more closely resembles clinical conditions. Gene expression profiles were compared by subtractive hybridization between ischemic and normal tissue of the same hearts. About one-third (23͞74) of the nuclear-encoded genes that were upregulated in ischemic myocardium participate in survival mechanisms (inhibition of apoptosis, cytoprotection, cell growth, and stimulation of translation). The specificity of this response was confirmed by Northern blot and quantitative PCR. Unexpectedly, this program also included genes not previously described in cardiomyocytes. Up-regulation of survival genes was more profound in subendocardium over subepicardium, reflecting that this response in stunned myocardium was proportional to the severity of the ischemic insult. Thus, in a swine model that recapitulates human heart disease, nonlethal ischemia activates a genomic program of cell survival that relates to the time course of myocardial stunning and differs transmurally in relation to ischemic stress, which induced the stunning. Understanding the genes up-regulated during myocardial stunning, including those not previously described in the heart, and developing strategies that activate this program may open new avenues for therapy in ischemic heart disease.apoptosis ͉ gene expression ͉ stunning O ne of the most important therapeutic targets in the treatment of cardiovascular disease has been the protection of ischemic myocardium from necrosis. This has been a major focus for basic and applied research over the past 30 years. More recently, mechanisms of programmed cardiac cell death (apoptosis) have also been studied extensively. Both necrosis and apoptosis result in the irreversible loss of contractile performance. An unexplored corollary to protection from cell death is the enhancement of cell survival. Our hypothesis is that myocardial ischemia elicits a genomic profile promoting cell survival, which would include the up-regulation of genes involved in prevention of apoptosis, cytoprotection, and cell growth. If a program of cell survival can be stimulated in the ischemic heart, it would represent a novel and important therapeutic strategy in the future.To address this hypothesis, we examined the genomic profile of ischemic myocardium in a model that is most relevant to clinical conditions, i.e., a swine model of transient ischemia.Although the majority of investigations on myocardial ischemia are conducted in rodent models, major differences exist between rodents and larger mammals (differences in heart rate, action potential, and calcium handling) (1, 2). We reasoned that th...

Glycolysis supplements energy synthesis at high cardiac workloads, producing not only ATP but also cytosolic NADH and pyruvate for oxidative ATP synthesis. Despite adequate Po(2), speculation exists that not all cytosolic NADH is oxidized by the mitochondria, leading to lactate production. In this study, we elucidate the mechanism for limited cytosolic NADH oxidation and increased lactate production at high workload despite adequate myocardial blood flow and oxygenation. Reducing equivalents from glycolysis enter mitochondria via exchange of mitochondrial alpha-ketoglutarate (alpha-KG) for cytosolic malate. This exchange was monitored at baseline and at high workloads by comparing (13)C enrichment between the products of alpha-KG oxidation (succinate) and alpha-KG efflux from mitochondria (glutamate). Under general anesthesia, a left thoracotomy was performed on 14 dogs and [2-(13)C]acetate was infused into the left anterior descending artery for 40 min. The rate-pressure product was 9,035 +/- 1,972 and 21,659 +/- 5,266 mmHg.beats.min(-1) (n = 7) at baseline (n = 7) and with dobutamine, respectively. (13)C enrichment of succinate was 57 +/- 10% at baseline and 45 +/- 13% at elevated workload (not significant), confirming oxidation of [2-(13)C]acetate. However, cytosolic glutamate enrichment, a marker of cytosolic NADH transfer to mitochondria, was dramatically reduced at high cardiac workload (11 +/- 1%) vs. baseline (50 +/- 14%, P < 0.05). This reduced exchange of (13)C from alpha-KG to cytosolic glutamate at high work indicates reduced shuttling of cytosolic reducing equivalents into the mitochondria. Myocardial tissue lactate increased 78%, countering this reduced oxidation of cytosolic NADH. The findings elucidate a contributing mechanism to glycolysis outpacing glucose oxidation in the absence of myocardial ischemia.