Radioimmunoassays for Human Melatonin

Birau, N.; Schloot, W.; Khoory, R.; Hofbauer, Harald F.; Röver, Christian; Birau, M.

doi:10.1016/b978-0-08-026400-4.50006-2

Cited by 3 publications

(3 citation statements)

References 7 publications

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“…Administration of melatonin in vivo determined a reduction of heart rate in baboon [22]and both arterial pressure and heart rate in rats [13]as the result of a hypothetical sympathetic inhibition. In fact, melatonin has been proposed as endogenous hypotensive factor probably by stimulating central inhibitory adrenergic pathways [23]. Our results firstly demonstrate that melatonin exerts a specific sympathetic antagonism in rat isolated papillary muscle which is an experimental model where central nervous system control and other hormonal influences are excluded.…”

Section: Discussionsupporting

confidence: 55%

Effects of melatonin in isolated rat papillary muscle

et al. 1997

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Melatonin (A r -acetyl-5-methoxytryptamine), the principal hormone of the vertebral pineal gland, elicits several neurobiological effects. However, the effects of melatonin on cardiac muscle are still unknown. The first goal of the study was to investigate the role of melatonin on myocardial contractility in isolated rat papillary muscle using dose-response curves to melatonin, to isoproterenol and calcium either in the presence or in the absence of melatonin (0.3 nM). Response curves to isoproterenol were additionally performed in the presence of melatonin plus the specific receptor antagonist 7V-acetyltryptamine (10 uM); the adenylate-cyclase stimulator forskolin (10 uM) was also used. Melatonin has no direct inotropic effect in isolated rat papillary muscle but counteracts isoproterenol but not [Ca 2+ ] effects. In fact, the EC50 for isoproterenol was significantly higher in the presence than in the absence of melatonin (p < 0.001). This antiadrenergic action occurs through an interaction to a specific cardiac receptor. Forskolin-stimulated adenylate cyclase induced an increase of contractile force (+118 ± 25%) which was reduced in the presence of melatonin (+26 ± 10%; p < 0.01).In conclusion, we found that melatonin possess anti-adrenergic effect in isolated rat papillary muscle. This phenomenon was abolished in the presence of its receptor antagonist TV-acetyltryptamine demonstrating that melatonin operates through a specific cardiac receptor. The reduction of contractility increase, induced by forskolin-stimulated adenylate cyclase, shows that melatonin may act through a reduction of cyclic AMP accumulation.© 1997 Federation of European Biochemical Societies.

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Section: Discussionsupporting

confidence: 55%

Effects of melatonin in isolated rat papillary muscle

et al. 1997

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“…The hormone has also shown a sinergic effect with contraceptives [182], and beneficial activity in the evolution and treatment of neoplastic diseases [183][184][185][186][187], and neuroprotective activity in cases of epilepsy [188]. Moreover, melatonin modifies some factors involved in cardiovascular pathology, aterogenesis [107], blood pressure in normotensive [108] and hypertensive persons [109], resistance of big vessels [110] and origin and evolution of cardiac arrhythmia [189]. Numerous scientists are investigating on other important functions like neutralizing of free radicals [67,92,93,157,190] and immunomodulation.…”

Section: Discussionmentioning

confidence: 99%

“…In fact, melatonin reduces platelet aggregation [105] and lipid oxidation [106], which are main causative factors for aterogenesis [107]. Furthermore, it reduces blood pressure in normotensive [108] and hypertensive subjects [109] and it decreases the resistance of the big vessels [110]. These actions…”

Section: Other Physiological Actionsmentioning

confidence: 99%

New Issues About Melatonin and its Effects on the Digestive System

Motilva¹,

Deogracias²,

Lastra

2001

CPD

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In human beings, melatonin is secreted in a cyclic way by the pineal gland, although it has been detected in other tissues. Synthesis of melatonin takes place in the pinealocyte. It depends on adrenergic stimulation, and its secretion is related to the photoperiod in a circadian model of low activity during light phase and high activity at night time. Former studies aimed to establish the mechanisms by which melatonin carries out its biological function, proved the existance of high affinity binding sites. However, melatonin can pass through the plasmatic membrane; this property suggested a possible activity of the hormone inside the cell trough activation of nuclear receptors. Moreover, melatonin can act by itself as a potent oxygen-free-radical scavenger, which renders it a very strong antioxidant. It is currently accepted that melatonin plays an important role in numerous physiological processes. The gastrointestinal tract of numerous animal species contains melatonin, which is synthesized essentially by intestinal enterochrommaffin cells. Some investigations have revealed that its liberation follows also a circadian rhythm, although its secretion pattern might be influenced by nutritional factors. Receptors for melatonin have been identified in the digestive system, therefore the indolamine might play a leading role in different aspects of the vast digestive physiopathology. The hormone may interact with receptors and subsequently stimulate the synthesis of gastroprotective hormones and also exerts a direct defense on the epithelium, enhances submucosal blood flow and prevents the damage induced by ischemia followed by reperfusion. Moreover, studies have shown that treatment with melatonin reduces the severity of the lesions induced by NSAIDs on gastric mucosa suggesting a beneficial role of melatonin in preventing this gastropathy related to antiinflammatories.

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Vascular Reactivity to Various Vasoconstrictor Agents and Endothelium-Dependent Relaxations of Rat Thoracic Aorta in the Long-Term Period of Pinealectomy

2006

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Abstract. In this study, the effects of reduced melatonin concentrations in the long-term period of pinealectomy on mean arterial blood pressure (BP) and vascular responses in isolated rat thoracic aorta were investigated. Rats were pinealectomized (Px) two months before the beginning of the studies. Rings of endothelium-intact and -denuded rat arteries were mounted in isolated tissue baths for the measurements of isometric contractile force. No significant difference was determined between the arterial BP of Px (88.1 ± 1.9 mmHg) and control (83.8 ± 1.2 mmHg) rats. All arteries isolated from control and Px rats showed essentially identical contractions in response to phenylephrine, serotonin, calcium, clonidine, vasopressin, and angiotensin-II. Only endothelin-1 (ET-1)-induced contractions in the endothelium-denuded vessels isolated from Px rats were found to be increased to some extent. Pinealectomy did not affect acetylcholine or sodium nitroprusside-induced relaxation in the rat aorta either. These data suggest that reduced melatonin levels two months after pinealectomy did not modify either the vascular reactivity to various vasoconstrictor agents except the partially increased contractile responses to ET-1 in the endothelium-denuded thoracic aortas of Px rats or the endotheliumdependent and -independent relaxations in rat thoracic aorta. Restoration of the increased vascular responses to some vasoconstrictor agents, which were reported previously, may be the reason of why the hypertension is temporary following pinealectomy.

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Radioimmunoassays for Human Melatonin

Cited by 3 publications

References 7 publications

Effects of melatonin in isolated rat papillary muscle

Effects of melatonin in isolated rat papillary muscle

New Issues About Melatonin and its Effects on the Digestive System

Vascular Reactivity to Various Vasoconstrictor Agents and Endothelium-Dependent Relaxations of Rat Thoracic Aorta in the Long-Term Period of Pinealectomy

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