Signaling responses after exposure to 5 alpha-dihydrotestosterone or 17 beta-estradiol in norepinephrine-induced hypertrophy of neonatal rat ventricular myocytes.

Androgens appear to enhance, whereas estrogens mitigate, cardiac hypertrophy. However, signaling pathways in cells for short (3 min) and longer term (48 h) treatment with 17beta-estradiol (E2) or 5 alpha-dihydrotestosterone (DHT) are understudied. We compared the effect of adrenergic stimulation by norepinephrine (NE; 1 microM) alone or in combination with DHT (10 nM) or E2 (10 nM) treatment in neonatal rat ventricular myocytes (NRVMs) by cell area, protein synthesis, sarcomeric structure, gene expression, phosphorylation of extracellular signal-regulated (ERK), and focal adhesion kinases (FAK), and phospho-FAK nuclear localization. NE alone elicited the expected hypertrophy and strong sarcomeric organization, and DHT alone gave a similar but more modest response, whereas E2 did not alter cell size. Effects of NE dominated when used with either E2 or DHT with all combinations. Both sex hormones alone rapidly activated FAK but not ERK. Long-term or brief exposure to E2 attenuated NE-induced FAK phosphorylation, whereas DHT had no effect. Neither hormone altered NE-elicited ERK activation. Longer term exposure to E2 alone reduced FAK phosphorylation and reduced nuclear phospho-FAK, whereas its elevation was seen in the presence of NE with both sex hormones. The mitigating effects of E2 on the NE-elicited increase in cell size and the hypertrophic effect of DHT in NRVMs are in accordance with results observed in whole animal models. This is the first report of rapid, nongenomic sex hormone signaling via FAK activation and altered FAK trafficking to the nucleus in heart cells.

High-dose statin therapy for secondary prevention of stroke: stroke prevention by aggressive reduction in cholesterol levels study review.

It has been shown that HMG-CoA (3-hydroxy-3-methylglutaryl coenzyme A) reductase inhibitors (statins) lower the incidence of a first stroke in patients with coronary heart disease, diabetes, or risk factors for cardiovascular disease. However, it is unknown whether statin therapy could reduce the incidence of a second stroke in patients without evidence of heart disease. This article reviews the results of the Stroke Prevention by Aggressive Reduction in Cholesterol Levels trial, a prospective, randomized, multicentered, double-blind, placebo-controlled, international trial designed to examine the effect of high-dose atorvastatin on secondary stroke prevention. Trial participants (4,731) had experienced a stroke or transient ischemic attack within 1 to 6 months before randomization into the study. Over the 5-year follow-up period, incidence of second stroke or transient ischemic attack was significantly reduced in the atorvastatin treatment group compared with the placebo group. In addition, high-dose atorvastatin therapy significantly decreased major coronary artery and other negative cardiovascular events. The reduction in incidence of secondary stroke was specific to ischemic stroke as opposed to hemorrhagic stroke. Results of the trial are clinically significant and support extension of the latest secondary stroke prevention guidelines to include statin therapy for those patients without coronary heart disease.

Cardiovascular risk factors and metabolic syndrome in alcohol- and nicotine-dependent men and women.

BACKGROUND AND RESEARCH OBJECTIVE: Cardiovascular disease (CVD) is a leading cause of mortality among alcohol-dependent people; however, minimal data exist on the CVD risk factor profile in this high-risk population. The purpose of this study was to examine the prevalence and clustering of traditional and novel CVD risk factors, including components of the metabolic syndrome, in nicotine- and alcohol-dependent adults. SUBJECTS AND METHODS: Participants (n = 46; 61% men; 87% white), who were a consecutive series of eligible adults (19-56 years of age; mean, 34.8 +/- 1.4 years; Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition-classified alcoholic; abstinent for or=25 kg/m2); 61% were physically inactive (<1,000 kcal/wk); and 61% had some form of hypertension. In addition, 54% had increased homocysteine values; high-sensitivity C-reactive protein was elevated in 28%; and 22% of the participants met criteria for metabolic syndrome. In this study of the CVD risk profile among alcoholics, subjects were found to have an average of 3 CVD risk factors in addition to cigarette smoking. This prevalence and clustering of potentially modifiable risk factors in young, nicotine-dependent alcoholics indicate the need for aggressive risk reduction focused on prevention of CVD.

Long-term effects of alcohol consumption in male and female rats.

Discrepancies exist regarding potential sex differences in the effects of ethanol on the myocardium. Therefore, the aims of this study were to determine if long-term ethanol consumption was associated with the development of a dilated cardiomyopathy (CM) in female rats and, second, to determine if the absence of ovarian hormones modulated this effect. Adult male and female (n=6-8/group) sham-operated and ovariectomized (OVX) Sprague-Dawley rats received the Lieber DeCarli ethanol-containing (8% vol/vol) or control liquid diet for 8 months. All ethanol groups showed echocardiographic evidence of a cardiomyopathy; however, more significant ethanol-elicited differences were found in the male ethanol group than in either the female or female OVX groups. In addition, the male ethanol group had significant reductions in in vivo measures of contractility, such as the maximum derivative of change in systolic pressure and preload recruitable stroke work. Sex differences were also apparent in the pattern and degree of posterior and septal wall thickness changes, in that the male ethanol group had more posterior and septal wall thinning. In conclusion, similar to male rats long-term ethanol consumption in gonad-intact and OVX female rats is associated with the development of a dilated cardiomyopathy.

Detection of cardiac variability in the isolated rat heart.

Cardiac variability can be assessed from two perspectives: beat-to-beat performance and continuous performance during the cardiac cycle. Linear analysis techniques assess cardiac variability by measuring the physical attributes of a signal, whereas nonlinear techniques evaluate signal dynamics. This study sought to determine if recurrence quantification analysis (RQA), a nonlinear technique, could detect pharmacologically induced autonomic changes in the continuous left ventricular pressure (LVP) and electrographic (EC) signals from an isolated rat heart-a model that theoretically contains no inherent variability. LVP and EC signal data were acquired simultaneously during Langendorff perfusion of isolated rat hearts before and after the addition of acetylcholine (n = 11), norepinephrine (n = 12), or no drug (n = 12). Two-minute segments of the continuous LVP and EC signal data were analyzed by RQA. Findings showed that%recurrence,%determinism, entropy, maxline, and trend from the continuous LVP signal significantly increased in the presence of both acetylcholine and norepinephrine, although systolic LVP significantly increased only with norepinephrine. In the continuous EC signal, the RQA trend variable significantly increased in the presence of norepinephrine. These results suggest that when either the sympathetic or parasympathetic division of the autonomic nervous system overwhelms the other, the dynamics underlying cardiac variability become stationary. This study also shows that information concerning inherent variability in the isolated rat heart can be gained via RQA of the continuous cardiac signal. Although speculative, RQA may be a tool for detecting alterations in cardiac variability and evaluating signal dynamics as a nonlinear indicator of cardiac pathology.

Effect of estrogen on calcium-handling proteins, beta-adrenergic receptors, and function in rat heart.

Regulation of cellular Ca(2+) cycling is central to myocardial contractile function. Loss of Ca(2+) regulation is associated with cardiac dysfunction and pathology. Estrogen has been shown to modify contractile function and to confer cardioprotection. Therefore, we investigated the effect of estrogen on expression of rat heart myocardial Ca(2+)-handling proteins and beta-adrenergic receptor (beta(1)-AR) and examined functional correlates. Female rats were sham-operated (SHAM) or ovariectomized. Two weeks after ovariectomy rats were injected (i.p.) daily with estradiol benozoate (OVX+EB) or sesame oil (OVX) for 2 weeks. Protein abundance was measured by immunoblotting and mRNA was quantified by real-time RT-PCR. OVX significantly decreased estrogen and progesterone levels and EB replacement returned both estrogen and progesterone to physiological levels. OVX induced a 75% reduction of uterine weight and a gain in body weight. Replacement restored weights to SHAM level. OVX increased and estrogen-replacement normalized abundance of beta(1)-AR and L-type Ca(2+) channel (Cav1.2) protein. OVX decreased sodium-Ca(2+) exchange protein (NCX) and estrogen restored protein abundance to SHAM levels. Sarcoplasmic reticular ATPase (SERCA), phospholamban (PLB), and ryanodine receptor (RyR) abundance was not altered by hormone status. Levels of mRNA encoding for beta(1)-AR, Cav1.2, and NCX were not influenced by OVX or estrogen replacement. OVX had no effect on SERCA and PLB mRNA level but estrogen replacement elicited a significant increase compared to OVX and SHAM. Estrogen-dependent changes in Ca(2+)-handling proteins and beta(1)-AR are theoretically consistent reduced myocellular Ca(2+) load. However, hormone-dependent alterations in protein were not associated with changes in contractile function.

Sex differences in susceptibility to epinephrine-induced arrhythmias.

Gender differences in incidence of cardiac arrhythmias have been documented. It is generally believed that cardiac pathology provides an arrhythmogenic substrate but that a trigger such as sympathetic nervous system activation is required to initiate arrhythmias. This study was done to determine whether there is a sex difference in susceptibility to epinephrine-induced arrhythmias in healthy rats without preexisting pathology and to determine whether gonadal hormones play a role in development of arrhythmias. Untreated, sham-operated, and gonadectomized male and female rats were anesthetized and given IV boluses of epinephrine. ECG, heart rate, and blood pressure were measured continuously for 1 minute and intermittently over a period of 30 minutes. Male rat hearts have a higher occurrence and frequency of epinephrine-induced premature ventricular contractions, missed beats, and blocks than female rat hearts. Ovariectomy increases arrhythmias, thereby abolishing the female advantage. Castration has no effect on occurrence and frequency of premature ventricular contractions but attenuates missed beats and blocks. Sex differences and effect of gonadectomy on epinephrine-induced alterations in heart rate and blood pressure implicate baroreceptor reflex in the dimorphic arrhythmogenic response. Male rat hearts are more susceptible than female hearts to epinephrine-induced arrhythmias, and gonadal hormones play a role in this disparity.

Sex differences in ethanol liquid diet consumption in Sprague-Dawley rats.

There are reports of sex differences in ethanol intake between different strains of male and female rats; however, ethanol consumption (via an ethanol liquid diet) and blood ethanol levels (BELs) between male and female rats of the Sprague-Dawley strain have not been studied. Therefore, the aims of this study were to examine body growth, ethanol consumption (ml/day and g.kg(-1).day(-1)), and BELs in adult male and female (n=6-8 per group; sham-operated and ovariectomized) Sprague-Dawley rats consuming different concentrations (3% to 9% volume/volume) of the Lieber-DeCarli liquid ethanol diet. Throughout the study, male rats weighed significantly more than both female groups, and ovariectomized female rats weighed more than sham female rats. Ethanol diet consumption (ml/day) was significantly greater in male rats than in female rats at higher ethanol concentrations, whereas, when the diet consumption was expressed in grams of ethanol per kilogram of body weight per day, the sham female group was shown to consume significantly more ethanol than the male group. Even though there were differences in ethanol intake, BELs were similar among the groups. The data indicate that, similar to other strains, Sprague-Dawley rats also exhibit sex differences in their pattern of body growth (weight gain) and ethanol intake; however, BELs were similar among the groups.

New blood thinner offers first potential alternative in 50 years: ximelagatran.

Traditional anticoagulants employed in the treatment of thrombosis include the injectable heparins and oral warfarin. Though effective, these traditional agents are fraught with limitations in their ease of use in the clinical setting. Warfarin, for example, has many pharmacokinetic properties and food-and-drug interactions that result in unpredictable patient response and the need for expensive and time-consuming monitoring of coagulation status. Ximelagatran is a novel, promising, orally active, direct thrombin inhibitor currently in development that, for the first time in 50 years, offers a potential alternative to the mainstay oral agent "warfarin." Advantages of ximelagatran over warfarin include predictable pharmacokinetics and pharmacodynamics, a broad therapeutic window, no routine anticoagulant monitoring, no clinically significant drug interactions, and fixed-dose administration. Ximelagatran has been evaluated for thromboprophylaxis following orthopedic surgery, acute treatment and secondary prevention of venous thrombosis, stroke prevention in atrial fibrillation, and acute coronary syndromes. Results of clinical trials suggest that ximelagatran is equally or more efficacious than warfarin and/or low-molecular-weight heparin therapy without increasing rates of minor or major bleeding. Although postmarketing surveillance will provide the final test of this drug, the future looks promising for addition of a new anticoagulant with the potential to provide excellent efficacy, predictable response, and reduced adverse effects. Pending regulatory approval, ximelagatran may help overcome barriers to appropriate anticoagulant therapy, thereby decreasing morbidity and mortality associated with thrombotic diseases.

Sex differences in the response of rat heart ventricle to calcium.

Calcium (Ca2+) is a key mediator of myocardial function. Calcium regulates contraction, and disruption of myocellular Ca2+ handling plays a role in cardiac pathologies such as arrhythmias and heart failure. This investigation examines sex differences in sensitivity of the contractile proteins to Ca2+ and myofibrillar Ca2+ delivery in the ventricular myocardium. Sensitivity of contractile proteins to Ca2+ was measured in weight-matched male and female Sprague-Dawley rats using the skinned ventricular papillary muscle fiber and Ca(2+)-stimulated Mg(2+)-dependent adenosine triphosphatase (ATPase) activity methodologies. Calcium delivery was examined by measuring the contractile response to a range of extracellular Ca2+ concentrations in isolated ventricular myocytes, papillary muscle, and the isolated perfused whole heart. Findings from studies in the whole heart suggest that at a fixed preload, the male left ventricle generates more pressure than a female ventricle over a range of extracellular Ca2+ concentrations. In contrast, results from myocyte and papillary muscle studies suggest that females require less extracellular Ca2+ to elicit a similar contractile response. Results obtained from the 2 methods used to determine sex differences in Ca2+ sensitivity were equivocal. Further studies are required to elucidate sex differences in myocardial Ca2+ handling and the reasons for disparate results in different heart muscle preparations. The results of these studies will lead to the design of sex-optimized therapeutic interventions for cardiac disease.

Estrogen plus progestin therapy: the cardiovascular risks exceed the benefits.

The surprising results of the Women's Health Initiative (WHI) reported in 2002 had a profound effect on women as well as health care practitioners. The WHI was the largest, randomized clinical trial designed to determine if postmenopausal hormone use prevented cardiovascular disease as well as other age-related disorders in women. While observational studies suggested that postmenopausal use of estrogen could decrease cardiovascular risk by 40% to 50%, the WHI demonstrated that use of continuous-combined estrogen plus progestin was not cardioprotective and was even associated with increased health risks. The estrogen alone trial of the WHI is still in progress, leaving practitioners and some women still in a dilemma. This article addresses the WHI in the context of other studies and discusses possible reasons for the unexpected results.

Subcellular distribution of protein kinase C isozymes during cardioplegic arrest.

BACKGROUND: On the basis of the hypothesis that cardioplegia-associated myocardial depression was due to activation of protein kinase C, we examined whether specific protein kinase C isozymes would translocate to a cellular fraction containing myofilaments. METHODS: Isolated rat hearts were perfused with Krebs-Ringer bicarbonate buffer for 30 minutes and arrested with 4 degrees C St Thomas No. 2 cardioplegic solution for 0 to 120 minutes (n = 5 per group). The 3 fractions of the left ventricle tissue represented the myofibrillar/nuclear fraction (P1), membranes (P2), and cytosol (supernatant). The distributions of protein kinase C isozymes alpha, delta, epsilon, and eta were examined after separation by electrophoresis, immunoblotting/chemiluminescence, and densitometry. RESULTS: A significant increase in protein kinase C-delta in the P1 fraction was detected after 5 minutes of cardioplegic arrest and remained increased for 60 minutes. Increases in P1 protein kinase C-alpha and -epsilon were seen transiently at 5 minutes, and protein kinase C-epsilon demonstrated a secondary increase in P1 at 30 to 60 minutes. There was also a significant relative increase in protein kinase C-alpha and protein kinase C-delta in the P2 fraction after 60 minutes of cardioplegia. CONCLUSIONS: These data are consistent with our hypothesis that activation of protein kinase C isozymes is associated with altered myofilament function after cardioplegic arrest.

Drug-eluting stents to prevent reblockage of coronary arteries.

Restenosis limits the success of percutaneous transluminal coronary interventions. Coronary artery stenting decreases restenosis, improves outcomes, and is currently the most commonly used percutaneous coronary intervention in the United States. However, in-stent restenosis continues to occur at an unacceptable rate. In-stent restenosis is a neointimal hyperplastic response resulting primarily from vascular smooth muscle cell proliferation. Treatment with anti-proliferative agents presents a logical approach to eradicating restenosis, however, these drugs are highly toxic. Coating stents with anti-proliferative agents allows local delivery of high doses and avoids systemic side effects. In 2001, the results of two clinical trials, RAVEL and ELUTES, using sirolimus- and paclitaxil-coated stents demonstrated nearly complete elimination of in-stent restenosis. These dramatic results represent a tremendous advance in the treatment of coronary heart disease.

Mechanisms of sex differences in rat cardiac myocyte response to beta-adrenergic stimulation.

The purpose of this study was to investigate sex differences in the functional response of isolated rat heart ventricular myocytes to beta-adrenergic stimulation and in isoproterenol-stimulated signal transduction. Fractional shortening was measured using a video edge-detection system in control- and isoproterenol-stimulated myocytes that had been isolated from weight-matched rats. Number and affinity of the beta-adrenergic receptors and the L-type Ca(2+) channel were measured in ventricular cardiac membranes by radioligand binding studies. Control- and isoproterenol-mediated alteration in Ca(2+) current density (I(Ca)) was determined by patch clamping and cellular cAMP content was determined by radioimmunoassay. Study results demonstrate that female myocytes have higher Ca(2+) channel density and greater I(Ca) than male myocytes. However, isoproterenol elicits a greater beta-adrenergic receptor-mediated increase cell shortening, I(Ca) and cAMP production in male myocytes. Male myocytes were also found to have a higher beta-adrenergic receptor density. These results suggest that cardiac myocytes from male rats have an enhanced response to beta-adrenergic stimulation due to augmented beta-adrenergic signaling that results in a greater transsarcolemmal Ca(2+) influx.