Tension cost correlates with mechanical and biochemical parameters in different myocardial contractility conditions

OBJECTIVES: Tension cost, the ratio of myosin ATPase activity to tension, reflects the economy of tension development in the myocardium. To evaluate the mechanical advantage represented by the tension cost, we studied papillary muscle contractility and the activity of myosin ATPase in the left ventricles in normal and pathophysiological conditions. METHODS: Experimental protocols were performed using rat left ventricles from: (1) streptozotocin-induced diabetic and control Wistar rats; (2) N-nitro-L-arginine methyl ester (L-NAME) hypertensive and untreated Wistar rats; (3) deoxycorticosterone acetate (DOCA) salt-treated, nephrectomized and salt- and DOCA-treated rats; (4) spontaneous hypertensive rats (SHR) and Wistar Kyoto (WKY) rats; (5) rats with myocardial infarction and shamoperated rats. The isometric force, tetanic tension, and the activity of myosin ATPase were measured. RESULTS: The results obtained from infarcted, diabetic, and deoxycorticosterone acetate-salt-treated rats showed reductions in twitch and tetanic tension compared to the control and sham-operated groups. Twitch and tetanic tension increased in the N-nitro-L-arginine methyl ester-treated rats compared with the Wistar rats. Myosin ATPase activity was depressed in the infarcted, diabetic, and deoxycorticosterone acetate salt-treated rats compared with control and sham-operated rats and was increased in N-nitro-L-arginine methyl ester-treated rats. These parameters did not differ between SHR and WKY rats. In the studied conditions (e.g., post-myocardial infarction, deoxycorticosterone acetate salt-induced hypertension, chronic N-nitro-L-arginine methyl ester treatment, and streptozotocin-induced diabetes), a positive correlation between force or plateau tetanic tension and myosin ATPase activity was observed. CONCLUSION: Our results suggest that the myocardium adapts to force generation by increasing or reducing the tension cost to maintain myocardial contractility with a better mechanical advantage

Eucalyptol, an essential oil, reduces contractile activity in rat cardiac muscle

Eucalyptol is an essential oil that relaxes bronchial and vascular smooth muscle although its direct actions on isolated myocardium have not been reported. We investigated a putative negative inotropic effect of the oil on left ventricular papillary muscles from male Wistar rats weighing 250 to 300 g, as well as its effects on isometric force, rate of force development, time parameters, post-rest potentiation, positive inotropic interventions produced by Ca2+ and isoproterenol, and on tetanic tension. The effects of 0.3 mM eucalyptol on myosin ATPase activity were also investigated. Eucalyptol (0.003 to 0.3 mM) reduced isometric tension, the rate of force development and time parameters. The oil reduced the force developed by steady-state contractions (50% at 0.3 mM) but did not alter sarcoplasmic reticulum function or post-rest contractions and produced a progressive increase in relative potentiation. Increased extracellular Ca2+ concentration (0.62 to 5 mM) and isoproterenol (20 nM) administration counteracted the negative inotropic effects of the oil. The activity of the contractile machinery evaluated by tetanic force development was reduced by 30 to 50% but myosin ATPase activity was not affected by eucalyptol (0.3 mM), supporting the idea of a reduction of sarcolemmal Ca2+ influx. The present results suggest that eucalyptol depresses force development, probably acting as a calcium channel blocker

Alkaloids in Erythrina

Erythrina species are used in popular medicine as sedative, anxiolytic, anti-inflammatory, and antihypertensive. In this work, we investigated the chemical composition of extracts obtained from leaves of E. falcata and E. crista-galli. The hypotensive potential of E. falcata and the mechanism of action were also studied. The extracts were obtained by maceration and infusion. The total content of phenolic compounds and flavonoids was estimated by spectrophotometric methods. The chemical constituents were studied performing a chromatographic analysis by UPLC-ESI-MS. For in vivo protocols, blood pressure and heart rate were measured by the invasive hemodynamic monitoring method. Different concentrations of extracts and drugs such as L-NAME, losartan, hexamethonium, and propranolol were administrated i.v. The results of total phenolic contents for E. falcata and E. crista-galli were 1.3193–1.4989 mgGAE/mL for maceration and 0.8771–0.9506 mgGAE/mL for infusion. In total flavonoids, the content was 7.7829–8.1976 mg RE/g for maceration and 9.3471–10.4765 RE mg/g for infusion. The chemical composition was based on alkaloids, suggesting the presence of erythristemine, 11β-methoxyglucoerysodine, erysothiopine, 11β-hydroxyerysodine-glucose, and 11-hydroxyerysotinone-rhamnoside. A potent dose-dependent hypotensive effect was observed for E. falcata, which may be related to the route of β-adrenergic receptors

Colesterolemia, trigliceridemia e excesso de peso em escolares de Santa Maria, RS, Brasil Blood lipids abnormalities and overweight prevalence in students of Santa Maria, RS, Brazil

INTRODUÇÃO: O nível de colesterol na infância é um preditor do nível de colesterol na vida adulta. As consequências do colesterol elevado, somadas a outros fatores de risco constituem problema mundial de saúde pública. OBJETIVO: Estimar a prevalência de hipercolesterolemia, hipertrigliceridemia e excesso de peso em estudantes do município de Santa Maria-RS. Métodos: Estudo transversal com 374 crianças de 10 a 12 anos de idade, de escolas das redes pública e privada, realizado no segundo semestre de 2005 na cidade de Santa Maria-RS. Foram determinados os níveis de colesterol total, triglicerídeos e estado nutricional. RESULTADOS: As prevalências de hipercolesterolemia, hipertrigliceridemia e excesso de peso encontradas foram de 4,7%, 8,9% e 20,7%, respectivamente. Não houve diferença significante entre sexo e rede pública e privada. As crianças com excesso de peso apresentaram maior prevalência de alterações lipídicas. CONCLUSÕES: A prevalência de alterações lipídicas pode ser considerada baixa, mas a prevalência de excesso de peso dos estudantes de Santa Maria mostrou-se relativamente alta, alertando à importância de políticas públicas e à necessidade de assistência pediátrica nessa faixa etária, visando o seu diagnóstico precoce e, principalmente, o aconselhamento nutricional e incentivo à prática esportiva, uma vez que as dislipidemias e o excesso de peso têm sido apontados como fatores de risco para as doenças cardiovasculares.<br>INTRODUCTION: Cholesterol level in childhood is a predictor of cholesterol level in adult life. The consequences of high cholesterol levels summed to other risk factors constitute a worldwide public health problem. OBJECTIVE: To estimate the prevalence of blood lipid abnormalities and overweight among school students of the city of Santa Maria, RS, Brazil. Methods: A cross-sectional study with 374 children, aged between 10 and 12 years, from public and private schools of the city of Santa Maria, RS, conducted on the second semester of 2005. Total cholesterol levels (TC), fractions of cholesterol (HDL- C and LDL- C), triglycerides (TG) and nutritional status were determined. RESULTS: The prevalence of hypercholesterolemia, hypertriglicemia and overweight found were 4.7%, 8.9% and 20.7%, respectively. There was no significant difference between sexes or public and private schools. The overweight children presented higher prevalence of lipid alterations. CONCLUSION: The prevalence of lipid alterations may be considered low, but the prevalence of overweight among the students of Santa Maria was high, demonstrating hence the importance of public policies and the need for pediatric assistance at this age group. The aims here would be early diagnosis, especially for nutritional advising and stimulus for physical activities, since overweight and blood lipid abnormalities have been pointed out as risk factors for cardiovascular diseases