Ventricular defibrillating properties of catecholamine uptake inhibitors.

Ventricular fibrillation (VF) is a fatal event in humans unless electrical defibrillation is applied within minutes. Recent publications describe spontaneous termination of VF in various animals and even in humans. Certain drugs can transfer a fatal, sustained VF (SVF) into a self-terminating, transient VF (TVF). Based on results obtained in animals of various species and ages, we have suggested that the occurrence of TVF requires a high cardiac catecholamine level at the time of VF. According to our hypothesis, drugs which decrease catecholamine reuptake by the sympathetic nerve terminals will increase the ability of the heart ventricles to defibrillate spontaneously. In the present study, we examined the effects of desipramine, maprotiline, mianserin, iprindole, cocaine and amphetamine on the type of VF in cats exhibiting SVF prior to the treatment. The results show that the ability of these compounds to transfer SVF to TVF is closely related to their potency to inhibit catecholamine reuptake. The establishment of the catecholamine related mechanisms of TVF may lead to the development of a new class of antiarrhythmic-defibrillatory drugs.     

Effect of berberine on catecholamine levels in rats with experimental cardiac hypertrophy

The aim of this study is to investigate the effect of berberine on catecholamine level (adrenaline and noradrenaline) in rats with experimental cardiac hypertrophy. Cardiac hypertrophy(CH) was induced by suprarenal abdominal aorta constriction, and the drugs were administered for 8 weeks starting from 4 weeks after surgery. The degree of cardiac hypertrophy was determined by heart and left ventricular weight. The level of adrenaline(AD) and noradrenaline(NA) was detected by HPLC. The data showed that in the CH model rats, the level of plasma and left ventricular tissue AD, and the level of NA in plasma were higher than that of the age-matched controls(indicating increased "total" sympathetic activity). The level of NA in left ventricular tissue of CH model rats was however lower than the age-matched controls. Berberine and captopril showed significant effect on inhibiting the development of cardiac hypertrophy. Berberine decreased plasma NA level and the AD level both in plasma and left ventricular tissue, but had no effect on improving the cardiac NA depletion. Captopril showed significant effect on increasing the depleted cardiac NA and in reducing the elevated plasma NA level. These findings show the efficacy of berberine on modulating the sympathetic nervous activity of rats with experimental cardiac hypertrophy, and reflect the therapeutic potentials of berberine in patients with cardiac hypertrophy and chronic heart failure.     

Phorbol ester stimulates catecholamine synthesis in isolated bovine adrenal medullary cells

In isolated bovine adrenal medullary cells, the phorbol ester 12-O-tetradecanoyl phorbol 13-acetate (TPA), an activator of protein kinase C, stimulated [14C]catecholamine synthesis from [14C]tyrosine, but not from [14C]DOPA. This stimulatory effect of TPA on [14C]catecholamine synthesis was not dependent upon extracellular Ca2+, and TPA did not affect the uptake of 45Ca2+ or the release of catecholamine by the cells. TPA also did not affect the intracellular cyclic AMP (cAMP) level. 4 alpha-Phorbol 12, 13-didecanoate, which is not an activator of protein kinase C, did not stimulate the synthesis of [14C]catecholamine from [14C]tyrosine. The stimulatory effect of TPA on [14C]catecholamine synthesis was additive with that of carbamylcholine, but not with that of dibutyryl cAMP (DB-cAMP). From these results, it was suggested that protein kinase C is involved in the regulation of tyrosine hydroxylase activity and that this regulatory mechanism might be similar to that involving cAMP.     

Effects of coenzyme Q(10) administration on its tissue concentrations,mitochondrial oxidant generation,and oxidative stress in the rat

Coenzyme Q (CoQ(10)) is a component of the mitochondrial electron transport chain and also a constituent of various cellular membranes. It acts as an important in vivo antioxidant, but is also a primary source of O(2)(-*)/H(2)O(2) generation in cells. CoQ has been widely advocated to be a beneficial dietary adjuvant. However, it remains controversial whether oral administration of CoQ can significantly enhance its tissue levels and/or can modulate the level of oxidative stress in vivo. The objective of this study was to determine the effect of dietary CoQ supplementation on its content in various tissues and their mitochondria, and the resultant effect on the in vivo level of oxidative stress. Rats were administered CoQ(10) (150 mg/kg/d) in their diets for 4 and 13 weeks; thereafter, the amounts of CoQ(10) and CoQ(9) were determined by HPLC in the plasma, homogenates of the liver, kidney, heart, skeletal muscle, brain, and mitochondria of these tissues. Administration of CoQ(10) increased plasma and mitochondria levels of CoQ(10) as well as its predominant homologue CoQ(9). Generally, the magnitude of the increases was greater after 13 weeks than 4 weeks. The level of antioxidative defense enzymes in liver and skeletal muscle homogenates and the rate of hydrogen peroxide generation in heart, brain, and skeletal muscle mitochondria were not affected by CoQ supplementation. However, a reductive shift in plasma aminothiol status and a decrease in skeletal muscle mitochondrial protein carbonyls were apparent after 13 weeks of supplementation. Thus, CoQ supplementation resulted in an elevation of CoQ homologues in tissues and their mitochondria, a selective decrease in protein oxidative damage, and an increase in antioxidative potential in the rat.     

Epinephrine sulfation in the forearm: Arteriovenous differences in free and conjugated catecholamines.

Simultaneously drawn arterial and forearm venous levels of free and sulfate conjugated epinephrine and norepinephrine were measured in 8 subjects in order to study the role of skeletal muscle in catecholamine sulfation. A sensitive radioenzymatic assay was used. The average free epinephrine level was 46% lower in venous than in arterial blood (p<0.023) while average sulfated epinephrine level was 37% higher (p<0.016). These findings suggest that epinephrine sulfation is occurring in the forearm, most likely in skeletal muscle. The mean venous free norepinephrine level was 21% higher than the mean arterial level (p<0.055) presumably reflecting release from sympathetic nerve terminals. No evidence of norepinephrine sulfation or deconjugation in skeletal muscle was found.     

人肾素转基因小鼠的建立

为研究人肾素基因在体内的功能和建立其药物干预实验的动物模型,采用显微注射法,将纯化的人肾素基因导入小鼠受精卵,再培育成转基因小鼠.通过DIG DNA印迹和PCR分析,进行转基因整合检测.在出生的13只子代鼠中,得到一只转基因阳性鼠.整合率为7.7%,有效率0.3%,转基因已稳定传代.RT-PCR显示转基因阳性鼠的肾、心和肺组织中有肾素基因表达,而在肝脏与骨骼肌中则未检测到.阳性鼠血浆肾素活性较对照鼠明显升高,而肾与心脏组织的肾素活性则无明显变化.人肾素转基因小鼠可用于研究循环或组织的RAS中肾素基因的功能及有关其药物抑制实验.     

The effect of three hypolipidemic drugs on catalase activity and peroxisomal and mitochondrial palmitate oxidation in rat cardiac and skeletal muscle

Catalase activity and peroxisomal and mitochondrial palmitate oxidation have been investigated in cardiac and skeletal muscle from rats fed clofibrate, ciprofibrate or nafenopin in an unrefined diet for different periods of time. Nafenopin was also added to either a high carbohydrate (70% of kilocalories from glucose) or high fat (70% of kilocalories from lard) diet and fed to rats for either 1 or 3 weeks. Catalase activity was elevated in all muscles from rats fed the hypolipidemic drugs. The response of catalase activity in muscle to clofibrate was dose-dependent. The response time of catalase activity was different in individual muscles. Peroxisomal palmitate oxidation was elevated in the heart and soleus muscle from rats fed nafenopin in either the high-carbohydrate or the high-fat diet. There was no change in peroxisomal palmitate oxidation in psoas or extensor digitorum longus muscle from rats fed the drugs. Mitochondrial palmitate oxidation was only slightly increased by nafenopin in the heart and soleus muscles after 3 weeks of nafenopin feeding. The results suggest that the cardiac muscle, like the liver, responds to hypolipidemic drug treatment with an increase in peroxisomal fat oxidation. The skeletal muscle response is less specific and that tissue may not contribute to the hypolipidemic effect of the drugs. The findings also suggest that these drugs do not induce peroxisome proliferation in skeletal muscle.     

Cardiovascular actions of dietary polyunsaturates and related mechanisms: A state-of-the-art-review

A survey of the effects of dietary polyunsaturates on the function of the cardiovascular system is given. In isolated hearts of rats dietary linoleate supply increases both coronary flow and heart muscle function. Hearts of rats fed high amounts of linoleic acid are protected against catecholamine (over)-stimulation. Polyunsaturate rich vegetable oils are effective in lowering blood pressure in several murine hypertension models. This effect seems to be closely related to antihypertensive changes in kidney function and in the function of the arterial vessel wall. Dietary polyunsaturates augment the hypotensive effect of antihypertensive drugs. Cardiovascular effects of dietary polyunsaturates are at least partly mediated via changes in the prostanoid metabolism as well as a reduction of the sympathetic activity.Evidence has been accumulated that cardiovascular effects of dietary polyunsaturates in animal and man are comparable. The observed effects are discussed against the background of a reduced risk of cardiovascular disease after a polyunsaturate rich diet in man.     

Decreased response of plasma catecholamine to stress in diabetic rats

Previously we reported that the heart norepinephrine concentration was markedly increased in diabetic rats. To further study the relationship between a disturbance in the autonomic nervous system and catecholamine metabolism in diabetes mellitus, the plasma catecholamine response to stress and catecholamine concentration of heart and adrenals were measured. Wistar male rats were made diabetic by streptozotocin and kept for 13 weeks. A silicon catheter was placed in the superior V. cava 1 week prior to the experiment. Insulin was injected subcutaneously for 3 days once daily. After an overnight fast and without anesthesia, 1 ml of blood, a control sample, was obtained and then the animals were exsanguinated. The blood was mixed with 1 mM EGTA at a final concentration and centrifuged. The tissue was homogenized with 0.4 N perchloric acid containing 1 mM EGTA and centrifuged at 10,000 x g for 20 minutes. Catecholamines were determined by high performance liquid chromatography. Normal rats responded to blood withdrawal stress, and plasma catecholamines were markedly increased, but almost no increase or an actual decrease was observed in diabetic rats. These abnormal responses were improved by insulin treatment. Heart norepinephrine was increased significantly in the diabetic rats compared with the control rats and was reduced significantly by insulin injections. Adrenal epinephrine was also significantly increased in the diabetic rats compared with the control rats, but was not significantly reduced by insulin. These result suggest a possible disturbance of catecholamine secretion in the diabetic rats.     

Effect of drugs on Trypanosoma cruzi and on its interaction with heart muscle cell "in vitro"

Megazol, nifurtimox, benznidazol and allopurinol were investigated, by light and electron microscopy, for their action on T. cruzi. Both the direct effect upon amastigote and trypomastigote forms and the effect upon the interaction of heart muscle cells (HMC) with bloodstream trypomastigotes were studied. The proliferation of amastigotes in Warren medium was inhibited in a dose-dependent manner by megazol, nifurtimox and benznidazol. Treatment of amastigotes (25-50 microM/24 h) and trypomastigotes (25 microM/24h) led to several ultrastructural alterations in the parasites. These three drugs also had a potent effect on the treatment of infected heart muscle cells when added at the beginning of the interaction or after one or three days of infection. The interiorized parasites showed a similar pattern of ultrastructural alterations as observed by the direct effect on the amastigotes. The primary heart muscle cell culture proved to be a suitable model for the study of drugs on intracellular parasites. Likewise, the amastigote proliferation in axenic medium was shown to be an adequate assay for an initial trial of drugs. These parameters seem very reliable to us for a systematic investigation of the mechanism of action of new drugs.     

Calcium transport systems in cardiac sarcolemma and their regulation by the second messengers cyclic AMP and calcium-calmodulin

The purpose of this survey is to describe the importance of cyclic AMP and Ca2+-calmodulin as mediators of the effects of beta-adrenergic agonists on cardiac sarcolemma. First, the basic characteristics of the three sarcolemmal Ca2+-transporting systems, the slow Ca2+ channel, the Ca2+-pumping ATPase and the Na+/Ca2+ antiporter, are described. These different pathways for in- and outflux of Ca2+ play a crucial role in the excitation-contraction coupling and relaxation of heart muscle. Catecholamines in the myocardium cause an increase in the rate and extent of tension development during systole, and in the rate of relaxation during diastole. These functional changes may largely be brought about by cyclic AMP-induced phosphorylation of membrane proteins that increases both the probability of opening the slow Ca2+ channels and the rate of Ca2+ pumping ATPase. It is generally believed that the effects on Ca2+ transport systems are due to direct actions of beta-adrenergic agonists leading to an increased cytosolic Ca2+ level during systole. Indirectly, an increase in systolic Ca2+ can amplify the primary effect of catecholamine on the Ca2+ pumping ATPase and probably also on the Na+/Ca2+ antiporter through Ca2+-calmodulin-dependent phosphorylation of membrane proteins. The intimate involvement of calmodulin in the operation of several sarcolemmal Ca2+-transporting systems is discussed in the light of the unknown mechanism of action of the so-called Ca2+ channel blockers, a class of drugs that have a very important potential to provide information on the fundamental reaction steps in excitation-contraction coupling. Some of these drugs are potent inhibitors of Ca2+-calmodulin-regulated enzymes.     

GDP and carboxyatractylate inhibit 4-hydroxynonenal-activated proton conductance to differing degrees in mitochondria from skeletal muscle and heart

The lipid peroxidation product 4-hydroxynonenal (HNE) increases the proton conductance of the inner mitochondrial membrane through effects on uncoupling proteins (UCPs) and the adenine nucleotide translocase (ANT); however, the relative contribution of the two carriers to these effects is unclear. To clarify this we isolated mitochondria from skeletal muscle and heart of wild-type and Ucp3 knockout (Ucp3KO) mice. To increase UCP3 expression, some mice were i.p. injected with LPS (12 mg/kg body weight). In spite of the increased UCP3 expression levels, basal proton conductance did not change. HNE increased the proton conductance of skeletal muscle and heart mitochondria. In skeletal muscle, this increase was lower in Ucp3KO mice and higher in LPS-treated wild-type mice, and was partially abolished by GDP (UCPs inhibitor) and completely abolished by carboxyatractylate (ANT inhibitor) or addition of both inhibitors. GDP had no effect on HNE-induced conductance in heart mitochondria, but carboxyatractylate or administration of both inhibitors had a partial effect. GDP-mediated inhibition of HNE-activated proton conductance in skeletal muscle mitochondria was not observed in Ucp3KO mice, indicating that GDP is specific for UCP3, at least in muscle. Carboxyatractylate was able to inhibit UCP3, probably through an indirect mechanism. Our results are consistent with the conclusion that, in skeletal muscle, HNE-induced increase in proton conductance is mediated by UCP3 (30%) and ANT, whereas in the heart the increase is mediated by ANT and other carriers, possibly including UCP3.     

Catecholamine metabolism inhibitors and receptor blockades only partially suppress cardiac hypertrophy of juvenile visceral steatosis mice with systemic carnitine deficiency

To clarify the mechanism of cardiac hypertrophy in carnitine-deficient JVS mice, we studied the possible role of catecholamine metabolism. Cardiac hypertrophy occurs 2 weeks after birth. The turnover of norepinephrine in the ventricles of JVS mice at 2 weeks was 3 times that of control, but it was not different from control at 5 days when the heart weight was not changed. To evaluate the accelerated norepinephrine turnover, we examined the effects of catecholamine metabolism inhibitors (alpha-methyltyrosine and 6-hydroxydopamine) and catecholamine receptor blockades (propranolol, prazosin and yohimbine) on the ratio of heart weight to body weight (HW/BW) and on the augmented expression of atrial natriuretic peptide (ANP) and the down-regulated carnitine deficiency-associated gene expressed in ventricle (CDV-1). The HW/BW ratio in JVS mice treated with catecholamine metabolism inhibitors and receptor blockades was significantly lower than in JVS mice without treatment, but still higher than in controls treated with each drug and in JVS mice treated with carnitine. The HW/BW ratio of JVS mice with propranolol was not significantly different from that of JVS mice treated with catecholamine metabolism inhibitors and was significantly lower than that of JVS mice treated with prazosin and yohimbine. Northern blot analysis showed that the altered expression of ANP and CDV-1 was not corrected in the ventricles of JVS mice treated with any of the drugs except carnitine. These results suggest that the catecholamine metabolism accelerated in JVS mice ventricles at 2 weeks is not the major cause of cardiac hypertrophy, but probably promotes cardiac hypertrophy mainly through the beta-adrenergic signaling pathway. The aberrant gene expression of ANP and CDV-1 found in JVS mice seems to be independent of catecholamine metabolism, and mediated primarily by the systemic carnitine deficiency.     

Haemodynamic effects of beta-adrenergic blockade in hyperthyroid patients with and without heart failure.

Haemodynamic studies were performed in 10 patients with uncomplicated thyrotoxicosis and seven with thyrotoxic cardiac failure. The cardiac output of those with uncomplicated hyperthyroidism was higher than normal at rest. After 2 mg of intravenous propranolol there was a 13% fall but the level was still higher than normal. In patients with thyrotoxic cardiac failure the resting cardiac output was normal, but it fell after propranolol by 30% to subnormal levels. In both groups there was an increase in right heart pressures and fall in the rate of increase in arterial pressure, which indicated a decrease in myocardial contractility. These results indicate that increased autonomic activity is a compensatory phenomenon in hyperthyroid heart failure and that its abolition by beta-blocking drugs has a deleterious effect on cardiac function. They are therefore contraindicated in patients with thyrotoxic heart failure.     

Comparative Analysis of Expression of Genes Encoding Enzymes of Catecholamine Catabolism and Renalase in Tissues of Normotensive and Hypertensive Rats

Comparative analysis of expression of genes encoding enzymes of catecholamine catabolism (monoamine oxidases A and B (MAO A and MAO B) and catechol-O-methyl transferase (COMT)) and renalase has been carried out in tissues of normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). Among investigated tissues the highest level of mRNA of genes encoding key enzymes of catecholamine catabolism (MAO A, MAO B, COMT) was found in the heart of WKY rats. In SHR the mRNA levels of these genes were lower (p < 0.05–0.01), however, no similar changes were observed in the tissues studied in dependence of hypertension. The relative mRNA levels of the studied genes normalized versus actin mRNA significantly varied. In heart and kidney the relative level of COMT mRNA significantly exceeded the relative levels of both MAO A mRNA and MAO B mRNA. In the brain differences in mRNAs of MAOA, MAOB, and COMT were less pronounced. However, in all examined tissue the renalase mRNA level was much (at least 10–20-fold) lower than any other mRNA studied. Taking into consideration known correlations between mRNAs and corresponding protein products reported in the literature for many genes these results suggest that in the case of any catalytic scenarios proposed or even proved for renalase this protein cannot contribute to catecholamine degradation. It is also unlikely that the products of the renalase reaction, β-NAD(P)⁺ and hydrogen peroxide, can exhibit a hypotensive effect due to low expression of the renalase encoding gene.     

Reflex cardiovascular and ventilatory responses to increasing H+ activity in cat hindlimb muscle

Static exercise increases arterial pressure, heart rate, and ventilation, effects which are believed in part to arise reflexly from a metabolic stimulus in the working muscle. In anesthetized cats, we tested the hypothesis that intra-arterial injections of lactic and hydrochloric acid, which created levels of these substances in muscle similar to those seen during contraction, reflexly increased cardiovascular and ventilatory function. Hydrochloric acid (32 and 57 mM; 1 ml) injected into the arterial supply of the triceps surae decreased intramuscular pH from 7.26 +/- 0.05 to 7.17 +/- 0.05 (P less than 0.01) and reflexly increased arterial pressure (23 +/- 7 mmHg; P less than 0.01), heart rate (11 +/- 2 beats/min; P less than 0.001), and ventilation (187 +/- 72 ml/min; P less than 0.05). Static contraction of the triceps surae decreased intramuscular pH from 7.28 +/- 0.06 to 7.13 +/- 0.06 (P less than 0.01). Lactic acid was more potent in causing reflexes than was equimolar HCl. For example, lactic acid containing 4 mM lactate and 0.87 mM H+ reflexly increased arterial pressure, heart rate, and ventilation, whereas 0.87 mM HCl did not. Intra-arterial sodium lactate (13 and 33 mM) at a neutral pH had no effect on these variables. We conclude that contraction-induced accumulation of H+, especially that arising from lactic acid, might provide a metabolic stimulus to evoke reflex autonomic effects.     

Abnormalities in plasma catecholamine response and tissue catecholamine accumulation in streptozotocin diabetic rats: a possible role for diabetic autonomic neuropathy

Plasma catecholamine levels, determined by high performance liquid chromatography, were elevated in response to blood withdrawal in normal rats. Such a response was also observed in streptozotocin diabetic rats 2 and 6 weeks after disease onset, but was no longer seen at 13 weeks. Tissue (adrenal, heart, skin, kidney) catecholamine levels in diabetic rats were increased at 6 weeks as well as at 13 weeks. These abnormalities were corrected by insulin treatment in at least a part of diabetic rats. The present data suggest that there might be a catecholamine accumulation, which is later accompanied with an impairment of catecholamine secretion, in diabetic rats, and they gave a basis for an inference that similar changes might play some role in the pathogenesis of diabetic autonomic neuropathy in man.     

The effect of adrenaline and acetylcholine on the hypothalamic-hypophysial neurosecretion in the rat

Summary The present investigation was undertaken to study the effects of adrenaline and acetylcholine on the hypothalamic-hypophysial neurosecretory system in rats.The drugs were injected intraperitoneally and into the lateral brain ventricle. The water diuresis was measured (I group). The animals were killed 45 min after intraperitoneal and 20 min after intraventricular administration of the drugs for the histological observations on the neurosecretory system and the histochemical studies of catecholamines in this area (II group).The antidiuretic effect of adrenaline and acetylcholine was established. The antidiuresis was more remarkable following intraventricular treatment.There was no direct relationship between the amount of neurosecretory substance and ADH activity in the posterior pituitary in the short term experiment after intraperitoneal administration of these drugs.The rapid release of ADH from the posterior pituitary was accompanied with a remarkable output of neurosecretory substance from the neurosecretory cell bodies into the axons and these effects were considerable after intraventricular introduction of the drugs. Some neurosecretory cells in the state of the initial hyperfunction were observed. In the posterior pituitary the initial mobilisation of the neurosecretory material from the neurosecretory terminals following intraventricular introduction of the drugs was observed.The supraoptic nucleus seems to be more sensitive to acetylcholine and the paraventricular nucleus to adrenaline treatment.The significant vasodilatation in the posterior pituitary and in the area of the supraoptic nucleus following intraventricular acetylcholine introduction was established.According to the data described it is possible to expect the existence of control of the hypothalamic neurosecretory activity by means of adrenergic and cholinergic structures.I am very obliged to Prof. W. Bargmann for his stimulating interest in this Study. I am grateful to Dr. G. Leontieva and Dr. V. Govyrin for the possibility to use the fluorescence catecholamine method, to Dr. E. Zeimal and Prof. M. Michelson for using the method for intraventricular injections.     

Analytical method for ubiquinone-9 and ubiquinone-10 in rat tissues by liquid chromatography/turbo ion spray tandem mass spectrometry with 1-alkylamine as an additive to the mobile phase

We investigated the application of 1-alkylamines, as additives to the mobile phase, to a quantification method for ubiquinone-9 (CoQ9) and ubiquinone-10 (CoQ10) in rat thigh muscle and heart using liquid chromatography-tandem mass spectrometry (LC-MS/MS). In the optimization of the analytical method, we found that 1-alkylamines mixed with CoQ9 and CoQ10 in the turbo ion sprayed solution formed the 1-alkylammonium adduct molecules of these compounds during the ionization process and that the intensity of the adduct ions was considerably higher than that of the protonated molecules ([M+H]+) of these compounds. Furthermore, we investigated a variety of 1-alkylamines in the mobile phase for LC-MS/MS analysis to select the most appropriate 1-alkylamine for higher sensitivities of CoQ9 and CoQ10. After these examinations, we found that methylamine was the most suitable additive for the mobile phase, allowing a 12.5-fold gain in signal intensity in the full ion mass spectrum compared with that without methylamine. The internal standard (IS) used was ubiquinone-11 (CoQ11) for each analyte. The analytes and IS were extracted with methanol from the tissue homogenates at neutral pH and were injected into an LC-MS/MS with a turbo ion spray interface. The calibration curves for CoQ9 (5-500 microg/g in thigh muscle and 50-10,000 microg/g in heart) and CoQ10 (1-500 microg/g in thigh muscle and 10-10,000 microg/g in heart) showed good linearity. The method was precise; the relative standard deviations of the method for rat thigh muscle were not more than 13.5 and 9.0% for CoQ9 and CoQ10, respectively, and those for rat heart were not more than 6.7 and 5.4% for CoQ9 and CoQ10, respectively. The accuracies of the method for both rat thigh muscle and heart were good, with the deviations between the nominal concentration and calculated concentration of CoQ9 and CoQ10 typically being within 12.3 and 4.3%, respectively. This method provided reliable concentration levels for CoQ9 and CoQ10 in rat thigh muscle and heart.     

Melatonin and the cardiovascular system

Melatonin concentrations in serum, as well as urinary levels of its main metabolite, 6-sulphatoxymelatonin, decrease with age. In the course of aging, the frequency of heart diseases, both acute and chronic, systematically increases. The evidence from the last 10 years suggests that melatonin influences the cardiovascular system. The presence of vascular melatoninergic receptors/binding sites has been demonstrated; these receptors are functionally linked with vasoconstrictor or vasodilatory effects of melatonin. Melatonin can contribute in cardioprotection of the rat heart, following myocardial ischemia. It has been shown that patients with coronary heart disease have a low melatonin production rate, especially those with higher risk of cardiac infarction and/or sudden death. There are clinical data reporting some alterations of melatonin in human stroke and coronary heart disease. The suprachiasmatic nucleus and, possibly, the melatoninergic system may also modulate cardiovascular rhythmicity. Hypercholesterolemia and hypertension are the other age-related symptoms. People with high levels of LDL-cholesterol have low levels of melatonin. It has been shown that melatonin suppresses the formation of cholesterol by 38% and reduces LDL accumulation by 42%. A 10-20% reduction of cholesterol concentration in women using the B-oval pill has been observed. It is a very important because, even a 10-15% reduction in blood cholesterol concentration has bee shown to result in a 20 to 30% decrease in the risk of coronary heart disease. People with hypertension have lower melatonin levels than those with normal blood pressure. The administration of the hormone in question declines blood pressure to normal range. It has been observed that melatonin, even in a dose 1 mg, reduced blood pressure and decreased catecholamine level after 90 min in human subjects. Melatonin may reduce blood pressure via the following mechanisms: 1) by a direct effect on the hypothalamus; 2) as an antioxidant which lowers blood pressure; 3) by decreasing the level of catecholamines, or 4) by relaxing the smooth muscle in the aorta wall.