[Association between gestational weight gain and preterm birth: a retrospective epidemiological analysis in Wuhan].

OBJECTIVE: To understand the influence of gestational weight gain(GWG)on preterm birth in Wuhan. METHODS: The retrospective epidemiological study was conducted in Wuhan Medical and Health Center for Women and Children between 2012 and 2014. Women who went to this hospital for antenatal care or giving birth were selected. Information was collected by using questionnaires, health care manual and clinical records. We used restricted cubic spline and multivariate logistic regression analysis to study the relationship between GWG and preterm birth. RESULTS: A total of 11 323 pregnant women participated in the investigation with 11 020(97.32%)of them eligible for our study. The results from the restricted cubic spline indicated that after adjusting for confounding factors, a U-curve was observed for GWG and preterm births(non-linearity test P< 0.001). Multivariate logistic regression analysis also indicated that both inadequate GWG(weight gainP90)were independent risk factors for preterm birth compared with normal GWG(weight gain P10-P90)with odds ratios of 1.59(1.25-2.01)and 1.46(1.13-1.88), respectively. CONCLUSIONS: Inappropriate GWG was the risk factor for preterm birth. Weight monitoring should be strengthened for pregnant women to reduce risk of preterm birth.

Melatonin in the oral cavity: physiological and pathological implications.

BACKGROUND AND OBJECTIVES: The purpose of this article was to summarize what is known about the function of melatonin in the oral cavity. MATERIAL AND METHODS: Databases were searched for the relevant published literature to 30 November, 2013. The following search items were used in various combinations: melatonin, gingiva, periodontium, inflammation, herpes, alveolar bone, periodontal ligament, dental implants, xerostomia, methacrylate, chlorhexidine, cancer. The literature uncovered is summarized herein. RESULTS: Salivary melatonin levels exhibit a circadian rhythm with highest values at night. Melatonin has both receptor-mediated and receptor-independent actions in cells of the oral cavity. Melatonin is released into the saliva by the acinar cells of the major salivary glands and via the gingival fluid. Functions of melatonin in the oral cavity are likely to relate primarily to its anti-inflammatory and antioxidant activities. These actions may suppress inflammation of the gingiva and periodontium, reduce alveolar bone loss, abrogate herpes lesions, enhance osteointegration of dental implants, limit oral cancer, and suppress disorders that have a free radical component. Sublingual melatonin tablets or oral melatonin sprays and topical melatonin-containing gel, if used on a regular basis, may improve overall oral health and reduce mucosal lesions. CONCLUSION: Collectively, the results indicate that endogenously-produced and exogenously-applied melatonin are beneficial to the oral cavity.

Essential actions of melatonin in protecting the ovary from oxidative damage.

Free radicals and other reactive species are involved in normal ovarian physiology. However, they are also highly reactive with complex cellular molecules (proteins, lipids, and DNA) and alter their functions leading to oxidative stress. Oxidative damage may play a prominent role in the development of disorders that considerably influence female fertility. Melatonin, because of its amphiphilic nature that allows for crossing morphophysiological barriers, is an effective antioxidant for protecting macromolecules against oxidative stress caused by reactive species. The balance between reactive oxygen species and antioxidants within the follicle seems to be critical to the function of the oocyte and granulosa cells and evidence has accumulated showing that melatonin is involved in the protection of these cells. Melatonin appears to have varied functions at different stages of follicle development, oocyte maturation, and luteal stage. Melatonin concentration in the growing follicle may be an important factor in avoiding atresia, because melatonin in the follicular fluid reduces apoptosis of critical cells. Melatonin also has protective actions during oocyte maturation reducing intrafollicular oxidative damage. An association between melatonin concentrations in follicular fluid and oocyte quality has been reported; this would allow a preovulatory follicle to fully develop and provide a competent oocyte for fertilization. The functional role of reactive species and the cytoprotective properties of melatonin on the ovary from oxidative damage are summarized in this brief review.

Melatonin, energy metabolism, and obesity: a review.

Melatonin is an old and ubiquitous molecule in nature showing multiple mechanisms of action and functions in practically every living organism. In mammals, pineal melatonin functions as a hormone and a chronobiotic, playing a major role in the regulation of the circadian temporal internal order. The anti-obesogen and the weight-reducing effects of melatonin depend on several mechanisms and actions. Experimental evidence demonstrates that melatonin is necessary for the proper synthesis, secretion, and action of insulin. Melatonin acts by regulating GLUT4 expression and/or triggering, via its G-protein-coupled membrane receptors, the phosphorylation of the insulin receptor and its intracellular substrates mobilizing the insulin-signaling pathway. Melatonin is a powerful chronobiotic being responsible, in part, by the daily distribution of metabolic processes so that the activity/feeding phase of the day is associated with high insulin sensitivity, and the rest/fasting is synchronized to the insulin-resistant metabolic phase of the day. Furthermore, melatonin is responsible for the establishment of an adequate energy balance mainly by regulating energy flow to and from the stores and directly regulating the energy expenditure through the activation of brown adipose tissue and participating in the browning process of white adipose tissue. The reduction in melatonin production, as during aging, shift-work or illuminated environments during the night, induces insulin resistance, glucose intolerance, sleep disturbance, and metabolic circadian disorganization characterizing a state of chronodisruption leading to obesity. The available evidence supports the suggestion that melatonin replacement therapy might contribute to restore a more healthy state of the organism.

The false thyroid capsule: new findings.

PURPOSE: The false thyroid capsule is an important anatomical structure involved in thyroidectomy, yet it is rarely studied. This study aimed to define the anatomy of the false thyroid capsule, and its clinical significance. METHODS: A prospective study was performed involving 151 patients with goitre who underwent thyroid lobectomy. The anatomy of the false thyroid capsule was carefully documented intra-operatively. RESULTS: The false thyroid capsule enclosed the inferior and middle thyroid veins and the superior thyroid vessels, forming a mesentery-like structure by attaching to the gland. Once the unilateral lobe had been removed, the thyroid mesentery could be seen to have a C-shaped edge. The recurrent laryngeal nerve, inferior thyroid artery and parathyroid glands were located beneath the C-shaped edge of the thyroid mesentery. CONCLUSION: The thyroid mesentery is a distinctive structure that can be used as a guide for surgical dissection.

The photoperiod, circadian regulation and chronodisruption: the requisite interplay between the suprachiasmatic nuclei and the pineal and gut melatonin.

The current scientific literature is replete with investigations providing information on the molecular mechanisms governing the regulation of circadian rhythms by neurons in the suprachiasmatic nucleus (SCN), the master circadian generator. Virtually every function in an organism changes in a highly regular manner during every 24-hour period. These rhythms are believed to be a consequence of the SCN, via neural and humoral means, regulating the intrinsic clocks that perhaps all cells in organisms possess. These rhythms optimize the functions of cells and thereby prevent or lower the incidence of pathologies. Since these cyclic events are essential for improved cellular physiology, it is imperative that the SCN provide the peripheral cellular oscillators with the appropriate time cues. Inasmuch as the 24-hour light:dark cycle is a primary input to the central circadian clock, it is obvious that disturbances in the photoperiodic environment, e.g., light exposure at night, would cause disruption in the function of the SCN which would then pass this inappropriate information to cells in the periphery. One circadian rhythm that transfers time of day information to the organism is the melatonin cycle which is always at low levels in the blood during the day and at high levels during darkness. With light exposure at night the amount of melatonin produced is compromised and this important rhythm is disturbed. Another important source of melatonin is the gastrointestinal tract (GIT) that also influences the circulating melatonin is the generation of this hormone by the entero-endocrine (EE) cells in the gut following ingestion of tryptophan-containing meal. The consequences of the altered melatonin cycle with the chronodisruption as well as the alterations of GIT melatonin that have been linked to a variety of pathologies, including those of the gastrointestinal tract.

Drug-mediated ototoxicity and tinnitus: alleviation with melatonin.

This review evaluates the published basic science and clinical reports related to the role of melatonin in reducing the side effects of aminoglycosides and the cancer chemotherapeutic agent cisplatin, in the cochlea and vestibule of the inner ear. A thorough search of the literature was performed using available databases for the purpose of uncovering articles applicable to the current review. Cochlear function was most frequently evaluated by measuring otoacoustic emissions and their distortion products after animals were treated with cytotoxic drugs alone or in combination with melatonin. Vestibular damage due to aminoglycosides was evaluated by estimating hair cell loss in explanted utricles of newborn rats. Tinnitus was assessed in patients who received melatonin using a visual analogue scale or the Tinnitus Handicap Inventory. Compared to a mixture of antioxidants which included tocopherol, ascorbate, glutathione and N-acetyl-cysteine, melatonin, also a documented antioxidant, was estimated to be up to 150 times more effective in limiting the cochlear side effects, evaluated using otoacoustic emission distortion products, of gentamicin, tobramycin and cisplatin. In a dose-response manner, melatonin also reduced vestibular hair cell loss due to gentamicin treatment in explanted utricles of newborn rats. Finally, melatonin (3 mg daily) limited subjective tinnitus in patients. These findings suggest the potential use of melatonin to combat the ototoxicity of aminoglycosides and cancer chemotherapeutic agents. Additional studies at both the experimental and clinical levels should be performed to further document the actions of melatonin at the cochlear and vestibular levels to further clarify the protective mechanisms of action of this ubiquitously-acting molecule. Melatonin's low cost and minimal toxicity profile supports its use to protect the inner ear from drug-mediated damage.

Significance and application of melatonin in the regulation of brown adipose tissue metabolism: relation to human obesity.

A worldwide increase in the incidence of obesity indicates the unsuccessful battle against this disorder. Obesity and the associated health problems urgently require effective strategies of treatment. The new discovery that a substantial amount of functional brown adipose tissue (BAT) is retained in adult humans provides a potential target for treatment of human obesity. BAT is active metabolically and disposes of extra energy via generation of heat through uncoupling oxidative phosphorylation in mitochondria. The physiology of BAT is readily regulated by melatonin, which not only increases recruitment of brown adipocytes but also elevates their metabolic activity in mammals. It is speculated that the hypertrophic effect and functional activation of BAT induced by melatonin may likely apply to the human. Thus, melatonin, a naturally occurring substance with no reported toxicity, may serve as a novel approach for treatment of obesity. Conversely, because of the availability of artificial light sources, excessive light exposure after darkness onset in modern societies should be considered a potential contributory factor to human obesity as light at night dramatically reduces endogenous melatonin production. In the current article, the potential associations of melatonin, BAT, obesity and the medical implications are discussed.

Basic mechanisms involved in the anti-cancer effects of melatonin.

It is commonly accepted that melatonin (N-acetyl-5-methoxytryptamine), the most relevant pineal secretory product, has oncostatic properties in a wide variety of tumors and, especially, in those identified as being hormonedependent. The objective of the present article is to offer a global and integrative view of the mechanisms involved in the oncostatic actions of this indoleamine. Due to the wide spectrum of melatonin's actions, the mechanisms that may be involved in its ability to counteract tumor growth are varied. These include: a) antioxidant effects; b) regulation of the estrogen receptor expression and transactivation; c) modulation of the enzymes involved in the local synthesis of estrogens; d) modulation of cell cycle and induction of apoptosis; e) inhibition of telomerase activity; f) inhibition of metastasis; g) prevention of circadian disruption; h) antiangiogenesis; i) epigenetic effects; j) stimulation of cell differentiation; and k) activation of the immune system. The data supporting each of these oncostatic actions of melatonin are summarized in this review. Moreover, the list of actions described may not be exhaustive in terms of how melatonin modulates tumor growth.

Scientific basis for the potential use of melatonin in bone diseases: osteoporosis and adolescent idiopathic scoliosis.

The objective of this paper was to analyze the data supporting the possible role of melatonin on bone metabolism and its repercussion in the etiology and treatment of bone pathologies such as the osteoporosis and the adolescent idiopathic scoliosis (AIS). Melatonin may prevent bone degradation and promote bone formation through mechanisms involving both melatonin receptor-mediated and receptor-independent actions. The three principal mechanisms of melatonin effects on bone function could be: (a) the promotion of the osteoblast differentiation and activity; (b) an increase in the osteoprotegerin expression by osteoblasts, thereby preventing the differentiation of osteoclasts; (c) scavenging of free radicals generated by osteoclast activity and responsible for bone resorption. A variety of in vitro and in vivo experimental studies, although with some controversial results, point toward a possible role of melatonin deficits in the etiology of osteoporosis and AIS and open a new field related to the possible therapeutic use of melatonin in these bone diseases.

Clinical uses of melatonin: evaluation of human trials.

During the last 20 years, numerous clinical trials have examined the therapeutic usefulness of melatonin in different fields of medicine. The objective of this article is to review, in depth, the science regarding clinical trials performed to date. The efficacy of melatonin has been assessed as a treatment of ocular diseases, blood diseases, gastrointestinal tract diseases, cardiovascular diseases, diabetes, rheumatoid arthritis, fibromyalgia, chronic fatigue syndrome, infectious diseases, neurological diseases, sleep disturbances, aging and depression. Melatonin has been also used as a complementary treatment in anaesthesia, hemodialysis, in vitro fertilization and neonatal care. The conclusion of the current review is that the use of melatonin as an adjuvant therapy seems to be well funded for macular degeneration, glaucoma, protection of the gastric mucosa, irritable bowel syndrome, arterial hypertension, diabetes, side effects of chemotherapy and radiation in cancer patients or hemodialysis in patients with renal insufficiency and, especially, for sleep disorders of circadian etiology (jet lag, delayed sleep phase syndrome, sleep deterioration associated with aging, etc.) as well as in those related with neurological degenerative diseases (Alzheimer, etc.,) or Smith-Magenis syndrome. The utility of melatonin in anesthetic procedures has been also confirmed. More clinical studies are required to clarify whether, as the preliminary data suggest, melatonin is useful for treatment of fibromyalgia, chronic fatigue syndrome, infectious diseases, neoplasias or neonatal care. Preliminary data regarding the utility of melatonin in the treatment of ulcerative colitis, Crohn's disease, rheumatoid arthritis are either ambiguous or negative. Although in a few cases melatonin seems to aggravate some conditions, the vast majority of studies document the very low toxicity of melatonin over a wide range of doses.

Development and validation of new methods for the determination of melatonin and its oxidative metabolites by high performance liquid chromatography and capillary electrophoresis, using multivariate optimization.

Melatonin (N-acetyl-5-metoxytriptamine, MEL) has focused a lot of attention as consequence of its multiple functions. MEL is a potent endogenous antioxidant and a free radical scavenger that reacts with several sort of radicals generating various metabolites. Two of them are N1-acetyl-N2-formyl-5-methoxykynurenine (AFMK) and N1-acetyl-5-methoxykynurenine (AMK). These compounds are important because they have also antioxidant actions as well as other important biological properties. In the present work, we develop two methods to detect and quantify these compounds (MEL, AFMK and AMK) in the same sample. For this purpose we used an experimental design, and utilized high performance liquid chromatography (HPLC-DAD) and micellar electrokinetic chromatography (MEKC) techniques with diode array detector in both of them. The limit of detection/quantification for MEL, AFMK and AMK were respectively 44/94, 18/38 and 23/51 ng mL(-1) by using HPLC and 13/44, 37/124 and 47/156 ng mL(-1) by using MEKC. This is the first time that these compounds have been separated in the same chromatogram or electroferogram. The time of analysis was faster using MEKC. Furthermore, this technique showed better resolution but HPLC offered better limit of detection and quantification for metabolites. Both methods were validated and correlation coefficients were higher than 0.999 and the range of recovery of those methods were 99.6-103.7%. Precision was evaluated as repeatability and intermediate precision with relative standard derivation <5%. When a 5 microg mL(-1) solution of these compounds were analyzed with both methods we do not observed any statistically significance differences. Moreover, we analyzed 3COHM (cyclic-3-hydroximelatonin), another known metabolite of melatonin, by using the same methods. The employment of these methods will offer a useful tool to contribute to answer the role of MEL, AFMK and AMK in biological system and both methods can be used in routine analysis for these compounds.

Melatonin in relation to the "strong" and "weak" versions of the free radical theory of aging.

That free radicals and the damage they inflict are related to deteriorative cellular and organismal changes associated with aging and also with the development of a variety of age-related diseases is widely debated. There seems to be little doubt that free radical mutilation of essential molecules contributes to these conditions. Numerous investigators, on the basis of their experimental results, have drawn this conclusion. If the free radical theory of aging and disease development has validity, antioxidants could presumably be successfully used to delay the molecular destruction, cellular loss, and organismal death. In the current review we summarize the experimental data related to the utility of melatonin in protecting against reactive oxygen and reactive nitrogen species-induced cellular damage. While the data supporting a role for melatonin in forestalling aging and prolonging life span per se is not compelling, the findings related to melatonin's ability to reduce the severity of a variety of age-related diseases that have as their basis free radical damage is convincing. To date, the bulk of these investigations have been performed in experimental models of diseases in animals. It is now imperative that similar studies be conducted using humans whose quality of life may benefit from treatment with melatonin.

Melatonin inhibits fatty acid-induced triglyceride accumulation in ROS17/2.8 cells: implications for osteoblast differentiation and osteoporosis.

Melatonin is produced not only by the pineal gland but by cells of the bone marrow. Moreover, melatonin is known to promote osteogenic differentiation in several cell line models and in multipotential bone marrow mesenchymal stem cells. Fatty acids have been independently shown to direct such cells to acquire the phenotype and molecular characteristics of adipocytes. To examine the effect of melatonin on intracellular triglyceride accumulation, an indicator of adipogenic differentiation in the rat osteoblast-like ROS17/2.8 cell line, cells were incubated with added oleic acid (100 muM), fixed and stained with Oil Red O. Cellular lipid accumulation was quantitated by an Oil Red O method highly specific for triglycerides and expressed as a triglyceride accumulation index (TGAI, triglyceride per cell). Melatonin in nanomolar concentrations inhibited oleic acid-induced triglyceride accumulation. To identify the mechanism by which melatonin reduces triglyceride accumulation, cells were incubated with the two melatonin receptor antagonists, luzindole and S20928, or forskolin, a stimulator of adenylyl cyclase and cAMP production. These compounds prevented the inhibitory effect of melatonin on triglyceride accumulation, indicating that melatonin acts through known melatonin receptor-mediated mechanisms. In view of the previously demonstrated positive effects of melatonin in promoting osteoblastic differentiation in ROS17/2.8 cells and their reciprocal adipocytic differentiation induced by fatty acids, our observations may serve to relate the known age-related decreases of melatonin production, the shift in the bone marrow toward an adipocytic line of cell development, and the development of osteoporosis during aging.

The potential of melatonin in reducing morbidity-mortality after craniocerebral trauma.

Craniocerebral trauma (CCT) is the most frequent cause of morbidity-mortality as a result of an accident. The probable origins and etiologies are multifactorial and include free radical formation and oxidative stress, the suppression of nonspecific resistance, lymphocytopenia (disorder in the adhesion and activation of cells), opportunistic infections, regional macro and microcirculatory alterations, disruptive sleep-wake cycles and toxicity caused by therapeutic agents. These pathogenic factors contribute to the unfavorable development of clinical symptoms as the disease progresses. Melatonin (N-acetyl-5-methoxytryptamine) is an indoleamine endogenously produced in the pineal gland and in other organs and it is protective agent against damage following CCT. Some of the actions of melatonin that support its pharmacological use after CCT include its role as a scavenger of both oxygen and nitrogen-based reactants, stimulation of the activities of a variety of antioxidative enzymes (e.g. superoxide dismutase, glutathione peroxidase, glutathione reductase and catalase), inhibition of pro-inflammatory cytokines and activation-adhesion molecules which consequently reduces lymphocytopenia and infections by opportunistic organisms. The chronobiotic capacity of melatonin may also reset the natural circadian rhythm of sleep and wakefulness. Melatonin reduces the toxicity of the drugs used in the treatment of CCT and increases their efficacy. Finally, melatonin crosses the blood-brain barrier and reduces contusion volume and stabilizes cellular membranes preventing vasospasm and apoptosis of endothelial cells that occurs as a result of CCT.

Melatonin defeats neurally-derived free radicals and reduces the associated neuromorphological and neurobehavioral damage.

Melatonin and its metabolites are potent antioxidants by virtue of their ability to scavenge both oxygen-based and nitrogen-based radicals and intermediates but also as a consequence of their ability to stimulate the activity of antioxidative enzymes. Melatonin also prevents electron leakage from the mitochondrial electron transport chain thereby diminishing free radical generation; this process is referred to as radical avoidance. The fact that melatonin and its metabolites are all efficient radical scavengers indicates that melatonin is a precursor molecule for a variety of intracellular reducing agents. In specific reference to the brain, melatonin also has an advantage over some other antioxidants given that it readily passes through the blood-brain-barrier. This, coupled with the fact that it and its by-products are particularly efficient detoxifiers of reactive species, make these molecules of major importance in protecting the brain from oxidative/nitrosative abuse. This review summarizes the literature on two brain-related situations, i.e., traumatic brain and spinal cord injury and ischemia/reperfusion, and the neurodegenerative disease, amyotrophic lateral sclerosis, where melatonin has been shown to have efficacy in abating neural damage. These, however, are not the only age-associated neurodegenerative states where melatonin has been found to be protective.

Medical implications of melatonin: receptor-mediated and receptor-independent actions.

The functional versatility and diversity of melatonin has exceeded everyone's expectations. The evidence is substantial that melatonin has multiple receptor-mediated and receptor-independent actions. Considering the unexpectedly widespread distribution of cellular membrane receptors as well as the existence of nuclear binding sites/receptors and the fact that some of melatonin's actions are receptor-independent means that melatonin likely functions in every cell with which it comes in contact. This is highlighted by the fact that there are no morpho-physiological barriers to melatonin, e.g., the blood-brain barrier. In addition to its widespread actions, melatonin synthesis occurs in widely diverse tissues with its production not being relegated to the pineal gland. This should not be unexpected given that it is present throughout the animal kingdom including species that lack a pineal gland, e.g., insects, and in single cell organisms. In this review, only a few of melatonin's effects that involve the interaction of the indoleamine with receptors are described. These functions include the control of seasonal reproduction, modulation of sleep processes and influences on bone growth and osteoporosis. Among the actions of melatonin that are likely receptor independent and that are reviewed herein include its ability to neutralize free radicals which leads to a reduction in cataract formation, reducing oxidative stress due to exposure to hyperbaric hyperoxia, ameliorating hyperthyroidism and abating the toxicity of sepsis and septic shock. These actions alone speak to the diversity of beneficial effects of melatonin; however, the review is no way near exhaustive in terms of what melatonin is capable of doing. Because of its ubiquitous benefits, the pharmaceutical industry is developing melatonin analogues which interact with melatonin receptors. Clearly, the intent of the drugs is to take advantage of some of melatonin's numerous beneficial effects.

Apoptosis in primary lymphoid organs with aging.

Age-associated changes in the immune system are responsible for an increased likelihood of infection, autoimmune diseases, and cancer in the elderly. Immunosenescence is characterized by reduced levels of the peripheral naive T cell pool derived from thymus and the loss of immature B lineage cells in the bone marrow. Primary lymphoid organs, i.e., bone marrow and thymus, exhibit a loss of cellularity with age, which is especially dramatic in the thymus. A summary of major changes associated with aging in primary lymphoid organs is described in this article. The participation of apoptosis in cell loss in the immune system, a change associated with age, as well as a description of molecular machinery involved, is presented. Finally, the involvement of different hormonal and non-hormonal agents in counteracting apoptosis in thymus and bone marrow during aging is explained. Here, we underlie the important role of glucocorticoids as immunodepressors and melatonin as an immunostimulatory agent.

Melatonin and cell death: differential actions on apoptosis in normal and cancer cells.

Melatonin is a natural compound synthesized by a variety of organs. It has been shown to function as a cell-protective agent. Since 1994, when the first paper was published documenting the role of melatonin in apoptosis, the number of reports in this area has increased rapidly. Much of the research conducted falls into three major categories: first, the role of melatonin in inhibiting apoptosis in immune cells; second, the role of melatonin in preventing neuronal apoptosis and finally, the role of melatonin in increasing apoptotic cell death in cancer cells. The mechanisms whereby melatonin influences apoptosis have not clarified, although a number of mechanistic options have been suggested. Apoptotic cell death is a physiological phenomenon related to homeostasis and proper functioning of tissues and organs; however, a failure in the apoptotic program is related to a number of diseases. The participation of melatonin in apoptosis in numerous cell types and its potential importance in a variety of diseases such as immunodeficiency, neurodegeneration and cancer is summarized in this review.

Protection against oxidative protein damage induced by metal-catalyzed reaction or alkylperoxyl radicals: comparative effects of melatonin and other antioxidants.

Melatonin is a well-known hydroxyl radical (*OH) scavenger that protects DNA and lipids from free radical attack. In this paper, we studied the ability of melatonin to prevent oxidative damage to bovine serum albumin (BSA) induced by two different paradigms: the metal-catalyzed oxidation (MCO) induced by Cu(2+)/H(2)O(2) and the alkoxyl and alkylperoxyl radicals formed by the azo initiator 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH, 40 mM). The protective effects of melatonin were compared with 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox), glutathione (GSH), ascorbate, 3,4',5-trihydroxy-trans-stilbene (resveratrol, 0.1 microM-4 mM) and mannitol (50 microM-100 mM). Melatonin efficiently prevented protein modification induced by both models, as assayed by polyacrylamide gel electrophoresis and carbonyl content. Both trolox and ascorbate had an obvious pro-oxidant effect in the Cu(2+)/H(2)O(2) model, whereas both prevented BSA damage induced by AAPH. In the MCO model, the efficacy of GSH in terms of protein protection was higher than melatonin at relatively high concentrations (250 microM-4 mM); however, at lower concentrations (50-250 microM), the efficacy of melatonin was superior to GSH. D-Mannitol (50 microM-100 mM) and resveratrol did not protect BSA from the site-specific damage induced by Cu(2+)/H(2)O(2). On the other hand, the relative protective efficiency in the AAPH model was melatonin approximately trolox>GSH>ascorbate.