Made available in DSpace on 2014-10-09T12:32:41Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:08:43Z (GMT). No. of bitstreams: 1 03368.pdf: 999521 bytes, checksum: 101fd5f39ffb5c80aba1c0d2559f7de3 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

A prominent finding in the diabetic rat heart is a decrease in the rate at which the ventricular muscle can contract and relax. Since cardiac sarcoplasmic reticulum is thought to be intimately involved in muscle contraction and relaxation we studied the ability of diabetic rat cardiac sarcoplasmic reticulum to transport Ca²⁺ . Hearts were obtained from female Wistar rats 7, 30, 42, and 120 days after the induction of diabetes by a single i.v. injection of either alloxan (65 mg/kg) or streptozotocin (60 mg/kg). At all Ca²⁺ concentrations tested (0.2 μM-5.0 μM free Ca²⁺) cardiac sarcoplasmic reticulum obtained from 42 and 120 day diabetic rats showed a significant decrease in the rate of ATP-dependent tns-oxalate facilitated ²⁺ransport. This was accompanied by a decrease in Ca²⁺ -ATPase activity. The levels of long chain acylcarnitines associated with the microsomal sarcoplasmic reticulum preparation from 42 and 120 day diabetic rats were significantly higher than those present in sarcoplasmic reticulum from control rats. Palmitylcarnitine, the most abundant of the long chain acylcarnitines, in concentrations < 7 μM was found to be a potent time-dependent inhibitor of both Ca²⁺ transport and Ca²⁺ -ATPase in both control and diabetic rat sarcoplasmic reticulum preparations; inhibition of Ca²⁺ transport was found to be more marked in the control preparations. This would indicate that a degree of inhibition produced by the high endogenous levels of palmitylcarnitine may already be present in the diabetic rat heart preparations. Cardiac sarcoplasmic reticulum prepared from acutely diabetic rats (7 days) did not show any decrease in Ca²⁺ transport ability. Levels of long chain acylcarnitines associated with the microsomal preparation enriched in sarcoplasmic reticulum were also unchanged. Insulin treatment of diabetic rats could significantly increase the ability of cardiac sarcoplasmic reticulum to transport Ca²⁺, although at the time period obtested (30 days) the SR Ca²⁺ transport activity was only slightly depressed as compared to control. Insulin treatment also resulted in a slight, but non-significant, lowering of the levels of long chain acylcarnitines associated with the sarcoplasmic reticulum microsomal preparations. These findings suggest that the alteration in sarcoplasmic reticulum function in chronically diabetic rats may be due to the buildup of cellular long chain acylcarnitines which inhibit sarcoplasmic reticulum Ca²⁺ transport. The absence of any significant change in Ca²⁺ transport activity or levels of long chain acylcarnitines at 7 and 30 days suggests that the alterations in 42 and 120 day diabetic rats must be of gradual onset. Cardiac sarcoplasmic reticulum is known to be regulated by a number of factors, among them calmodulin, cAMP-dependent protein kinase, and K⁺. Since Ca²⁺ transport activity in cardiac sarcoplasmic reticulum from chronically diabetic rats is depressed, the role that these regulators play was investigated. Calmodulin (0.61 μM), cAMP (10 μM) plus cAMP-dependent protein kinase (0.2 mg/0.5 ml), and K⁺ (0-110 mM) all stimulated Ca transport in both control and streptozotocin-treated diabetic rats to the same degree. This suggests that the depression observed in sarcoplasmic reticulum function from diabetic rats is not due to altered regulation by these putative mediators of Ca²⁺ uptake. A number of studies suggest that carnitine administration may lower myocardial levels of long chain acylcarnitines in the diabetic rat. Therefore, D,L-carnitine (1 g/kg/day, orally) was administered to 120 day diabetic rats for a 30 day period. The elevated levels of long chain acylcarnitines normally seen in diabetic rats were significantly reduced in the diabetic rats administered carnitine. Carnitine administration, however, could not reverse the previously noted depression in diabetic rat heart function, as measured on an isolated working heart apparatus. In an effort to prevent the onset of the diabetic cardiomyopathy D,L-carnitine was administered (3 g/kg/day, orally) 3 days after the induction of diabetes for a 42 day period. As previously mentioned, sarcoplasmic reticulum Ca²⁺ transport activity was depressed in diabetic rats, as compared to control rats, at all free Ca²⁺ concentrations tested (0.1 μM-3.5 μM). Similarly, sarcoplasmic reticulum levels of long chain acylcarnitines were significantly elevated in these diabetic rats. The diabetic rats treated with carnitine did not show any depression in Ca²⁺ transport activity; long chain acylcarnitine levels were also similar to control. The carnitine-treated diabetic rats, however, showed no improvement in heart function compared to untreated-diabetic rats. These data suggest that although the long chain acylcarnitines are inhibiting cardiac sarcoplasmic reticulum function in chronically diabetic rats other factors must also be contributing to the depression in heart function. / Pharmaceutical Sciences, Faculty of / Graduate

The nature and extent of myocardial ischemic injury (Mil) produced either by coronary artery ligation/reperfusion or by injection of isoproterenol (ISO) was studied in the 10-week alloxan-diabetic rabbit. Prior to the induction of ischemic injury, investigation of the left ventricles of the diabetic rabbit after 10-weeks revealed significant magnesium depletion and inhibition of myofibrillar and sarcoplasmic reticulum ATPase activities. In addition, the activity of the lysosomal enzyme, N-acetyl-β-glucosaminidase was significantly increased in diabetic left ventricular homogenates. Ultrastructural studies revealed significant lipid and glycogen accumulation, dilatation of the sarcoplasmic reticulum and damage to the mitochondria in left ventricles of the diabetic animals. Administration of ISO to both control and diabetic animals resulted in atrial tachycardias and ventricular fibrillation. The severity of the arrhythmias and the overall mortality was the same in both groups of animals. Serum analyses revealed significantly greater increases in blood glucose, free fatty acids, total cholesterol and creatine kinase activity in the ISO-treated diabetic animals relative to ISO-treated controls. ISO treatment of both control and diabetic animals produced similar increases in heart weight, left ventricular weight and myocardial water content. Analyses of various subcellular organelle marker enzyme activities indicated a significantly greater decrease in the K⁺ ,Ca²⁺ -stimulated sarcoplasmic reticulum ATPase of ISO-treated diabetic animal hearts. In addition, significantly greater increases in Ca and hydroxyproline and decreases in the levels of ATP were evident in the ISO-treated diabetic animal hearts. Ultra-structural studies revealed significant damage to the mitochondria in both ISO-treated control and diabetic hearts, the magnitude of the damage being greater in the diabetic animals. Mitochondria from both groups of animals showed swelling and fragmentation, myofibrils appeared as a homogeneous mass and did not show the characteristic Z-lines. Glycogen depletion and lipid accumulation was observed in both groups of animals. In addition, both groups of animals showed amorphous dense bodies in the mitochondria after ISO-treatment. After 40-minutes occlusion of the left circumflex coronary artery followed by 60-minutes of reperfusion, hemodynamic measurements revealed significant decreases in the left ventricular and systemic arterial pressures in the diabetic animals relative to controls. Analyses of subcellular organelle enzymes from the ischemic tissue revealed that sarcolemmal Na⁺ ,K⁺ -ATPase, mitochondrial ATPase and sarcoplasmic reticulum ATPase activities were decreased after coronary occlusion in both control and diabetic animals. However, upon reperfusion, unlike the control, no recovery of the mitochondrial ATPase was observed in the diabetic animals. In addition, a further depression of both the sarcolemmal and sarcoplasmic reticulum ATPase activities were seen in the diabetic animals compared to controls on reperfusion. Ion measurements revealed a significant accumulation of calcium in both control and diabetic animals, the magnitude of the increase being greater in the diabetic animals. Similarly, both tissue ATP levels and the ability of the mitochondria to generate ATP were depressed in the diabetic animals as compared to controls following coronary artery occlusion and reperfusion. Following coronary artery ligation and reperfusion, the diabetic animals showed a significantly higher incidence of ventricular fibrillation and cardiogenic shock as compared to controls. Ultrastructural studies revealed myocardial damage to both control and diabetic hearts following coronary artery ligation and reperfusion. However, the diabetic myocardium showed a higher incidence and frequency of hypercontraction bands, an increase in the amorphous dense bodies and slightly greater damage to the mitochondria. Coronary artery ligation in conscious control, 6 and 12 week-diabetic rats resulted in post-ligation arrhythmias (especially ventricular fibrillation), the incidence of which was much greater in the diabetic animals. The mortality rate of 12-week diabetic rats undergoing coronary ligation was 100% within 1-7 minutes following ligation. No differences in occluded or infarcted zones of the surviving 6-week diabetic and control rats were detected. Analyses of ionic composition revealed a significant magnesium deficiency in the diabetic hearts as compared to controls. These data indicate that the diabetic animals show a greater susceptibility of the myocardium to ischemic injury. Although numerous metabolic and chemical alterations are present in the diabetic myocardium, it is possible that magnesium deficiency may be a factor determining the higher incidence of arrhythmias and ischemic injury in diabetic animals. / Pharmaceutical Sciences, Faculty of / Graduate

In the present study, we examined whether NF-κB activation is required for cardiac hypertrophy in vivo. Cardiac hypertrophy in rats was induced by aortic banding for 1, 3, and 5 days and 1-6 wk, and age-matched sham-operated rats served as controls. In a separate group of rats, an IκB-α dominant negative mutant (IκB-αM), a superrepressor of NF-κB activation, or pyrrolidinedithiocarbamate (PDTC), an antioxidant that can inhibit NF-κB activation, was administered to aortic-banded rats for 3 wk. The heart weight-to-body weight ratio was significantly increased at 5 days after aortic banding, peaked at 4 wk, and remained elevated at 6 wk compared with age-matched sham controls. Atrial natriuretic peptide and brain natriuretic peptide mRNA expressions were significantly increased after 1 wk of aortic banding, reached a maximum between 2 and 3 wk, and remained increased at 6 wk compared with age-matched sham controls. NF-κB activity was significantly increased at 1 day, reached a peak at 3 wk, and remained elevated at 6 wk, and IKK-β activity was significantly increased at 1 day, peaked at 5 days, and then decreased but remained elevated at 6 wk after aortic banding compared with age-matched sham controls. Inhibiting NF-κB activation in vivo by cardiac transfection of IκB-αM or by PDTC treatment significantly attenuated the development of cardiac hypertrophy in vivo with a concomitant decrease in NF-κB activity. Our results suggest that NF-κB activation is required for the development of cardiac hypertrophy in vivo and that NF-κB could be an important target for inhibiting the development of cardiac hypertrophy in vivo.

Myocardial bridging is a congenital coronary anomaly with normal epicardial coronary artery taking an intra-myocardial course also described as tunneled artery. The majority of patients with this coronary anomaly are asymptomatic and generally it is a benign condition. However, it is an important cause of myocardial ischemia, which may lead to anginal symptoms, acute coronary syndrome, cardiac arrhythmias and rarely sudden cardiac death. There are numerous studies published in the recent past on understanding the pathophysiology, diagnostic and management strategies of myocardial bridging. This review highlights some of the recent updates in the diagnosis and management of patients with myocardial bridging. We discuss the role of various non-invasive and invasive diagnostic methods to evaluate functional significance of bridging. In addition, role of medical therapy such as beta-blockers, percutaneous coronary intervention with stents/bioresorbable scaffolds and surgical unroofing in patients unresponsive to medical therapy is highlighted as well.

No description available.

No description available.

No description available.

No description available.

Yes / Superoxide anions have been associated with many aspects of cardiovascular disease. Menadione is a superoxide anion donor that alters the heart’s electrical and mechanical functions. The aim of this study was to demonstrate simultaneous changes in intracellular Ca2+ ([Ca2+]i) and mechanical activity in intact adult cardiac myocytes, and mechanical activity and electrical activity in isolated whole hearts in order to provide greater insight into the mechanisms associated with the detrimental effects of menadione on the myocardium. Isolated hearts from adult male Wistar rats (n = 11, 200–250 g) were Langendorff perfused at 38°C with a Krebs–Henseleit solution. A saline-filled balloon was placed in the left ventricle (LV) in order to measure diastolic and developed pressure. Monophasic action potentials were simultaneously recorded from the epicardial surface. External stimulation at 5 Hz and intrinsic pacing were used throughout a 10 min control period and 30 min exposure to 50 μM menadione. Single LV myocytes (n = 7 from n = 4 animals) were loaded with the Ca2+-indicator Fura4-AM, stimulated at 1 Hz and exposed to 50 μM menadione. Myocyte length was simultaneously measured with [Ca2+]i using a video edge detection system. In isolated hearts, exposure to menadione significantly decreased contractility and action potential duration (with a similar time course); intrinsic heart rate and rhythmicity. Diastolic pressure was significantly increased. In single adult myocytes, menadione caused a significant increase in diastolic [Ca2+]i and a decrease in resting cell length and led to spontaneous release of [Ca2+]i. We conclude that the effects of menadione upon electrical and mechanical activity of the heart are at least in part a consequence of dysregulation of [Ca2+]i handling and the subsequent increase in diastolic [Ca2+] alterations in [Ca2+]i are consistent with the generation of delayed after depolarization arrhythmias.