Acute treatment of constant darkness increases the efficiency of ATP synthase in rat liver mitochondria

The circadian oscillations of many physiological processes provide an endogenous temporal program for the adaptive synchronization of mammals to the fluctuating external world. The lack of exposure to light causes the circadian system to undergo a process of dark adaptation similar to dark adaptation in the visual system. The aim of the present work was investigate the effect of acute treatment of constant darkness on mitochondrial ATP synthase activities and membrane fluidity in liver from male rat. We found that ATP synthase activity was not changed by the treatment. However ATPase activity and membrane fluidity were significantly diminished and pH gradient driven by ATP hydrolysis was incremented, in comparison from samples from rats kept on normal light/dark cycles. Additionally, the treatment of constant darkness diminishes the passive proton permeability of the inner mitochondrial membrane. In conclusion constant darkness induces a more efficient coupling between proton transport and catalysis, and increment the efficiency of the enzyme because the ratio of ATP synthase/ATPase activity was higher. These results exhibited the physiological adaptation of liver mitochondria to acute treatment of constant darkness in order to satisfy the cellular energy demand.

Apolipoprotein E genotypes in Mexican patients with Parkinson's disease

Background: The association of the apolipoprotein (Apo E) -epsilon4 allele to neurodegenerative diseases such as Parkinson’s disease (PD) has been analyzed in several studies. This association has been identified by amyloid deposits and neurofibrillary tangles in the brains of patients with neurodegenerative diseases.

Method: In this study the possible relationship between Apo E alleles and PD patients was analyzed in 105 patients with PD and 107 healthy controls from a Mexican population.

Results: Allele analysis in PD vs. controls was: ε2 in 6% and 2.3%, respectively; ε3 in 73% and 88.3%; and ε4 in 21% and 9.4%. The ε3 allele showed a protective risk effect with an Odds ratio (OR) of 0.36 (95%CI 0.20-0.61) and p < 0.05; contrary results were observed for the ε4 allele, which showed an increased risk for PD, with an OR of 2.57(95% CI 1.42-4.79) and p < 0.05. Upon multivariate analysis showed PD risk was evident in patients who were carriers of the genotype ε3/ε4; age group (fifty or more years) and had exposure to pesticides and solvents (p < 0.05).

Conclusions: The ε3/ε3; ε3/ε4 genotypes of the Apo E, were positively associated with sporadic PD.

Scanning electron microscopy of the orbital Harderian gland in the male Atlantic bottlenose dolphin (Tursiops truncatus)

The ultrastructure of the Harderian gland of Atlantic bottlenose dolphin (Tursiops truncatus) was examined by scanning electron microscopy (SEM). We found the following surface features: the typical round appearance of the ascinar glandular unit with a finely granular surface, a thin cortex and immediately below two types of cells: type I cells (characterized by small lipid vacuoles) and type II cells (characterized by large lipid vacuoles). It has been suggested that different cells forms represent a single cell type in varying activity states. Additionally, a coalescent tubular complex, a small balloon-like structures and large globular structures were observed. These structures may be reservoirs of secretion products.

Oxidative stress is increased in serum from Mexican patients with relapsing-remitting multiple sclerosis

OBJECTIVE

To determine the oxidative stress markers in serum from patients with relapsing-remitting multiple sclerosis.

METHODS

Blood samples from healthy controls and 22 patients 15 women (7 aged from 20 to 30 and 8 were > 40 years old) and 7 men (5 aged from 20 to 30 and 2 were > 40 years old) fulfilling the McDonald Criteria and classified as having Relapsing-Remitting Multiple Sclerosis accordingly with Lublin were collected for oxidative stress markers quantification.

RESULTS

Nitric oxide metabolites (nitrates/nitrites), lipid peroxidation products (malondialdehyde plus 4-hidroxialkenals), and glutathione peroxidase activity were significantly increased in serum of subjects with relapsing-remitting multiple sclerosis in comparison with that of healthy controls. These data support the hypothesis that multiple sclerosis is a component closely linked to oxidative stress.

[The effect of ibuprofen and acetylsalicylic acid on cognitive impairment, total antioxidant power and isoprostane serum]

INTRODUCTION

There are controversial studies on the prevention of Alzheimer's disease with nonsteroidal antiinflammatory drugs (NSAIDs). The objective of this study was to evaluate the effect of ibuprofen and acetylsalicylic acid on cognitive impairment, serum total antioxidant power (TAP) and isoprostane (8-iso-PGF2alpha).

METHODS

From April 2004 to February 2006, a Folstein mini-mental state (MMSE), Syndrome Kurtz Test (SKT) and a geriatric depression scale (Yasevage) were applied to eighteen, 55-56 years old eligible women. All women (n= 18) with normal cognitive state were randomized to ibuprofen 400 mg per day (n= 9) and acetylsalicylic acid 500 mg per day (n= 9) for one year. Serum TAP and 8-iso-PGF2alpha were performed at baseline, after six months and one year of treatment.

RESULTS

After one year of treatment with acetylsalicylic acid five women (55.6%) raised their score 4 points in MMSE compared with 3 points increased (33.3%) showed by the ibuprofen group. TAP increased (p=0.01) and 8-iso-PGF2alpha reduced (p=0.01) in both groups compared with baseline.

CONCLUSIONS

Both drugs improved the cognitive state andoxidative status of our population.

Protective effects of melatonin against caustic esophageal burn injury in rats

Caustic ingestion is one of the most life-threatening events in the pediatric age group, which requires the immediate management and subsequent treatment of its most significant complication, i.e. alterations in esophageal structure. We investigated whether melatonin could reduce the esophageal burn damage induced by sodium hydroxide. It was assumed that melatonin could be effective because of its function as a direct free radical scavenger, its antioxidative actions and its ability to diminish tissue hydroxyproline (HP) levels. Esophageal burns were induced in male rats by the administration of 10% sodium hydroxide. Lipid peroxidation (LPO) products were then measured at the following times: 0, 1, 6, 24, 48 and 72 hr after treatment. Tissue HP concentrations in the injured area were assessed at 14 days after the administration of sodium hydroxide. The groups received either systemic melatonin or normal saline. There were two, non-ischemic, sham control groups treated with or without melatonin. LPO products, malondialdehyde (MDA) and 4-hydroxyalkenal (4-HDA), increased immediately after the administration of sodium hydroxide; this indicates the participation of free radicals in the development of damage. Melatonin diminished the oxidative response and the amount of HP in the late phase of the lesion. Melatonin reduced oxidative damage in the early phase of the esophageal burns induced by sodium hydroxide.

The Orbital Harderian Gland of the Male Atlantic Bottlenose Dolphin (Tursiops truncatus): A Morphological Study

The ultrastructure of the Atlantic Bottlenose dolphin Harderian gland (HG) has been described but some questions remain unanswered. The purpose of this work was to define the gland's structure, ultrastructure and the differences between cells (types I and II) of the male dolphin using optic, fluorescence and electron transmission microscopy. Three different cells were observed under optic and fluorescence microscopic examination, while only two cell types (types I and II) were distinguished by electron transmission microscopy. Type I (oval nuclear envelope) exhibited three different cell populations and type II (indented nuclear envelope) exhibited two different cell populations. Although, we observed both types of vesicles in both types of cells they differed, principally, in quantity. The glands also possessed prominent duct systems, with three orders of complexity. The dolphin orbital HG appears to function as a mixed heterologous gland with two types of cells that exhibit both types of vesicles and other distinguishable differences.

Monosodium glutamate-induced damage in liver and kidney: a morphological and biochemical approach

It has been demonstrated that high concentrations of monosodium glutamate in the central nervous system induce neuronal necrosis and damage in retina and circumventricular organs. In this model, the monosodium glutamate is used to induce an epileptic state; one that requires highly concentrated doses. The purpose of this study was to evaluate the toxic effects of the monosodium glutamate in liver and kidney after an intra-peritoneal injection. For the experiment, we used 192 Wistar rats to carry out the following assessments: a) the quantification of the enzymes alanine aminotransferase and aspartate aminotransferase, b) the quantification of the lipid peroxidation products and c) the morphological evaluation of the liver and kidney. During the experiment, all of these assessments were carried out at 0, 15, 30 and 45 min after the intra-peritoneal injection. In the rats that received monosodium glutamate, we observed increments in the concentration of alanine aminotransferase and aspartate aminotransferase at 30 and 45 min. Also, an increment of the lipid peroxidation products, in kidney, was exhibited at 15, 30 and 45 min while in liver it was observed at 30 and 45 min. Degenerative changes were observed (edema-degeneration-necrosis) at 15, 30 and 45 min.

Effects of melatonin on the nitric oxide treated retina

AIMS

Nitric oxide (NO) is a free radical which reportedly causes damage to living cells. This study evaluated the damaging effect of NO and the protection of melatonin on the retina in vivo.

METHODS

Female Wistar rats (230-250 g) received two intraperitoneal injections of either melatonin (5 mg/kg) or vehicle alone. After general anaesthesia, the animals received 1 microl intravitreal injections of 0.9% saline and 1 mM sodium nitroprusside (SNP) into the right eye and the left eye, respectively. The animals were divided into two groups and then sacrificed after 24 hours (day 1) and 96 hours (day 4). The mean inner retinal layer thickness (mIRLT), the number of retinas expressing hyperchromatic (HC) nuclei in the inner nuclear layer (INL) and the apoptotic ganglion cell detection were compared.

RESULTS

After 1 day, SNP significantly increased the mIRLT by 45% (p = 0.004), initiated more INL nuclear HC expression (p = 0.01) and apoptotic nuclei (p<0.05) compared with the control eyes. Injection of melatonin ameliorated these changes. On day 4, SNP demonstrated similar effects in all parameters on the retina. After the injection of melatonin, both INL HC expression and apoptotic ganglion nuclei in the SNP treated eyes were similar to the controls but the mIRLT was significantly greater than in controls (p = 0.006).

CONCLUSION

Uncontrolled NO elevation caused morphological and nuclear changes in the retina. Melatonin significantly suppressed the NO induced increase in mIRLT, INL HC expression, and apoptotic ganglion cells on day 1, but not after day 4. Melatonin may have a protective role in the NO elevated retina.

Scanning electron microscopy of the superficial pineal gland of the 15-day-old rat (Rattus norvegicus)

The presence of a cortex and medulla in the superficial pineal gland has been a controversial point in the morphology of this structure in mammals. The published reports indicate contradictory data especially in rodents. In this study the pineal gland of 15-day-old male rats (Rattus norvegicus) were studied, using scanning electron microscopy, in an attempt to determine whether or not a cortex and medulla are apparent in the pineal gland of young rats. The superficial pineal gland of the 15-day-old rat exhibited both a cortex and a medulla; these areas exhibited different structural organizations. The cortex had a thickness of 40-80 microm and the cells did not show a particular arrangement. The center of the gland was composed of a medulla, which had a width of 1000-1200 microm, and consisted of cells arranged in cords; its morphology was distinctly different from that of the cortex.

N-acetylserotonin suppresses hepatic microsomal membrane rigidity associated with lipid peroxidation

N-acetylserotonin, the immediate precursor of melatonin in the tryptophan metabolic pathway in the pineal gland, has been reported to be an antioxidant. The aim of this work was to test the effect of N-acetylserotonin in stabilizing biological membranes against oxidative stress. Hepatic microsomal membranes from male adult rats were incubated with N-acetylserotonin (0.001-3 mM) before inducing lipid peroxidation using FeCl(3), ADP and NADPH. Control experiments were done by incubating microsomal membranes with N-acetylserotonin in the absence of lipid peroxidation-inducing drugs. Membrane fluidity was assessed by fluorescence spectroscopy and malonaldehyde plus 4-hydroxyalkenals concentrations were measured to estimate the degree of lipid peroxidation. Free radicals induced by the combination of FeCl(3)+ADP+NADPH produced a significant decrease in the microsomal membrane fluidity, which was associated with an increase in the malonaldehyde plus 4-hydroxyalkenals levels. These changes were suppressed in a concentration-dependent manner when N-acetylserotonin was added in the incubation buffer. In the absence of lipid peroxidation, N-acetylserotonin (0.001-3 mM) did not change membrane fluidity nor malonaldehyde plus 4-hydroxyalkenals levels. These results suggest that the protective role of N-acetylserotonin in preserving optimal levels of fluidity of the biological membranes may be related to its ability to reduce lipid peroxidation.

Melatonin, vitamin E, and estrogen reduce damage induced by kainic acid in the hippocampus: potassium-stimulated GABA release

Melatonin, vitamin E and estrogen have been shown to exert neuroprotective effects against kainic acid (KA)-induced damage in the hippocampus. The aim of the present study was to examine the changes in potassium-evoked gamma-aminobutyric acid (GABA) release in the hippocampus of KA-treated rats and to test the possible protective effects of melatonin, vitamin E or estrogen. Following the treatment of mice with KA, a marked reduction in potassium-evoked [3H]GABA release was observed. Melatonin or estrogen prevented the reduction in potassium-evoked GABA release due to kainate administration. Vitamin E also exhibited some protective effect, but it was less than that provided by melatonin or estrogen. Melatonin, estrogen and, to a lesser extent, vitamin E reduce the physiological toxicity of KA. Since KA is believed to cause neuronal alterations via oxidative processes, it is assumed that the free radical scavenging and oxidative properties of melatonin, estrogen and vitamin E account for the protective effects of these agents.

Characterization of the protective effects of melatonin and related indoles against alpha-naphthylisothiocyanate-induced liver injury in rats

The protective effect of melatonin, 6-hydroxymelatonin and N-acetylserotonin against alpha-naphthylisothiocyanate (ANIT)-induced liver injury was investigated and compared in rats injected once with the hepatotoxicant (75 mg/kg body weight). In rats injected with ANIT alone, liver injury with cholestasis developed within 24 h, as indicated by both serum levels of alanine aminotransferase (SGPT) and aspartic acid aminotransferase (SGOT) activities and serum total bilirubin concentration. The administration of melatonin or 6-hydroxymelatonin (10 mg/kg body weight) to ANIT-injected rats reduced significantly the serum levels of both SGPT and SGOT and the serum total bilirubin concentration. For all hepatic biochemical markers, melatonin was more effective that 6-hydroxymelatonin. By comparison, the administration of N-acetylserotonin (10 mg/kg body weight) to ANIT-injected rats did not reduce the serum levels of either hepatic enzymes or the serum total bilirubin concentration. In ANIT-injected rats, hepatic lipid peroxidation (LPO) was significantly higher than in control animals and this increase was significantly reduced by either melatonin, 6-hydroxymelatonin or N-acetylserotonin. Furthermore, ANIT treatment caused a significant reduction in liver microsomal membrane fluidity and this reduction was completely reversed by the three indoles. The liver from ANIT-injected rats showed several histopathological alterations; above all there was an acute infiltration of polymorphonuclear neutrophils and an increase in the number of apparent apoptotic hepatocytes. The concurrent administration of melatonin reduced the severity of all morphological alterations, specially the neutrophil infiltration and the number of presumed apoptotic cells. On the contrary, the administration of 6-hydroxymelatonin or N-acetylserotonin did not provide any protective effect in terms of the histopathological alterations. These results indicate that melatonin protects against ANIT-induced liver injury with cholestasis in rats, and suggests that this protective effect is likely due to its antioxidant properties and above all to its capacity to inhibit liver neutrophil infiltration, a critical factor in the pathogenesis of ANIT-induced liver injury. 6-hydroxymelatonin, although able to provide partial protection against the ANIT-induced hepatic injury, probably through its antioxidant properties by mechanisms that are unclear, was unable to reduce neutrophil infiltration. Finally, N-acetylserotonin in the experimental conditions of this study, only exhibited some antioxidant protection but had no protective effect against ANIT-induced hepatic damage.

Characterization of the protective effects of melatonin and related indoles against alpha-naphthylisothiocyanate-induced liver injury in rats

The protective effect of melatonin, 6-hydroxymelatonin and N-acetylserotonin against alpha-naphthylisothiocyanate (ANIT)-induced liver injury was investigated and compared in rats injected once with the hepatotoxicant (75 mg/kg body weight). In rats injected with ANIT alone, liver injury with cholestasis developed within 24 h, as indicated by both serum levels of alanine aminotransferase (SGPT) and aspartic acid aminotransferase (SGOT) activities and serum total bilirubin concentration. The administration of melatonin or 6-hydroxymelatonin (10 mg/kg body weight) to ANIT-injected rats reduced significantly the serum levels of both SGPT and SGOT and the serum total bilirubin concentration. For all hepatic biochemical markers, melatonin was more effective that 6-hydroxymelatonin. By comparison, the administration of N-acetylserotonin (10 mg/kg body weight) to ANIT-injected rats did not reduce the serum levels of either hepatic enzymes or the serum total bilirubin concentration. In ANIT-injected rats, hepatic lipid peroxidation (LPO) was significantly higher than in control animals and this increase was significantly reduced by either melatonin, 6-hydroxymelatonin or N-acetylserotonin. Furthermore, ANIT treatment caused a significant reduction in liver microsomal membrane fluidity and this reduction was completely reversed by the three indoles. The liver from ANIT-injected rats showed several histopathological alterations; above all there was an acute infiltration of polymorphonuclear neutrophils and an increase in the number of apparent apoptotic hepatocytes. The concurrent administration of melatonin reduced the severity of all morphological alterations, specially the neutrophil infiltration and the number of presumed apoptotic cells. On the contrary, the administration of 6-hydroxymelatonin or N-acetylserotonin did not provide any protective effect in terms of the histopathological alterations. These results indicate that melatonin protects against ANIT-induced liver injury with cholestasis in rats, and suggests that this protective effect is likely due to its antioxidant properties and above all to its capacity to inhibit liver neutrophil infiltration, a critical factor in the pathogenesis of ANIT-induced liver injury. 6-hydroxymelatonin, although able to provide partial protection against the ANIT-induced hepatic injury, probably through its antioxidant properties by mechanisms that are unclear, was unable to reduce neutrophil infiltration. Finally, N-acetylserotonin in the experimental conditions of this study, only exhibited some antioxidant protection but had no protective effect against ANIT-induced hepatic damage.

Protective role of melatonin against MPTP-induced mouse brain cell DNA fragmentation and apoptosis in vivo

OBJECTIVES

1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a neurotoxin that induces a Parkinsonian-type syndrome in animals which is similar to Parkinson's disease in humans. MPTP toxicity partially depends on the production of free radicals which in turn play a key role in the apoptotic death of neurons. In the present study melatonin, a potent free radical scavenger with antiapoptotic properties, was given to determine whether it would reduce oxidative stress in mice treated with MPTP.

MATERIALS AND METHODS

Male mice were given MPTP with or without melatonin and the brain was studied either 6h, 24h, 7 days or 15 days after the last MPTP injection.

RESULTS

The results show that melatonin counteracted in vivo MPTP-induced apoptosis in midbrain neurons at 6 and 24 h after MPTP treatment, and partially prevented apoptosis at 7 and 15 days after MPTP administration. MPTP treatment also produced time-dependent cell damage, whereas melatonin reduced the percentage of damaged cells at all time points, the effect being most evident at 15 days after treatment. Moreover, melatonin counteracted MPTP-dependent DNA fragmentation in the midbrain and striatum at 7 and 15 days after drug administration.

CONCLUSION

These results support a role for melatonin in protecting neurons against MPTP toxicity in vivo, and suggest that its antiapoptotic action is one of the mechanisms by which melatonin protects neuronal cells from neurotoxic insults.

Different patterns in the histology and autofluorescence of the Harderian glands of the Syrian Hamster, rat, mouse, Mongolian gerbil and guinea pig

The purpose of this study was to compare the natural fluorescence in the Harderian glands of the Syrian hamster, rat, mouse, Mongolian gerbil and guinea pig (both sexes). For each species, 10 animals (five males and five females) were used. Histological autofluorescence studies were performed using a fluorescence microscope (450-490 nm filter). Two different types of fluorescent cells were observed in both hamster (type AFI high intensity and type AFII, low fluorescence) and rat (type AFI, low fluorescence and type AFII, high fluorescence) Harderian glands. The fluorescence was basally located in all mice cells, whereas it was observed near the epithelial cell nuclei in the Mongolian gerbil (occupying two-thirds and one-third of the cells in males and females, respectively). A high intensity of fluorescence was present throughout the acinar cells in the guinea pig. The patterns of fluorescence identified exhibited a sexual dimorphism in all species studied. These results demonstrate that the Harderian glands of the animal species examined exhibit a variety of histological autofluorescence patterns.

Melatonin-induced increased activity of the respiratory chain complexes I and IV can prevent mitochondrial damage induced by ruthenium red in vivo

Melatonin displays antioxidant and free radical scavenger properties. Due to its ability with which it enters cells, these protective effects are manifested in all subcellular compartments. Recent studies suggest a role for melatonin in mitochondrial metabolism. To study the effects of melatonin on this organelle we used ruthenium red to induce mitochondrial damage and oxidative stress. The results show that melatonin (10 mg/kg i.p.) can increase the activity of the mitochondrial respiratory complexes I and IV after its administration in vivo in a time-dependent manner; these changes correlate well with the half-life of the indole in plasma. Melatonin administration also prevented the decrease in the activity of complexes I and IV due to ruthenium red (60 microg/kg i.p.) administration. At this dose, ruthenium red did not induce lipid peroxidation but it significantly reduced the activity of the antioxidative enzyme glutathione peroxidase, an effect also counteracted by melatonin. These results suggest that melatonin modulates mitochondrial respiratory activity, an effect that may account for some of the protective properties of the indoleamine. The mitochondria-modulating role of melatonin may be of physiological significance since it seems that the indoleamine is concentrated into normal mitochondria. The data also support a pharmacological use of melatonin in drug-induced mitochondrial damage in vivo.

Genotoxicity of paraquat: micronuclei induced in bone marrow and peripheral blood are inhibited by melatonin

The ability of melatonin to influence paraquat-induced genotoxicity was tested using micronucleated polychromatic erythrocytes as an index of damage in both bone marrow and peripheral blood cells of mice. Melatonin (10 mg/kg) or an equal volume of saline were administered intraperitoneally (ip) to mice 30 min prior to an ip injection of paraquat (20 mg/kgx2), and thereafter at 6-h intervals until the conclusion of the study (72 h). The number of the micronucleated polychromatic erythrocytes increased after paraquat administration both in peripheral blood and bone marrow cells. Melatonin administration to paraquat-treated mice significantly reduced micronuclei formation in both peripheral blood and bone marrow cells; these differences were apparent at 24, 48 and 72 h after paraquat administration. The induction of micronuclei was time-dependent with peak values occurring at 24 and 48 h. The reduction in paraquat-related genotoxicity by melatonin is likely due in part to the antioxidant activity of the indole. We did not observe effects of melatonin over paraquat in paraquat+melatonin groups incubated at 0, 60 and 120 min. Mitomycin C, which was used as a positive control, also caused the expected large rises in micronuclei in both bone marrow and peripheral blood cells at 24, 48 and 72 h after its administration.

Role of pinoline and melatonin in stabilizing hepatic microsomal membranes against oxidative stress

We investigated the influence of pinoline (0.01-1.5 mM) on microsomal membrane fluidity before and after rigidity was induced by oxidative stress. In addition, we tested the effect of pinoline in the presence of 1 mM melatonin. The fluidity in rat hepatic microsomes was monitored using fluorescence spectroscopy and it was compared to the inhibition of malonaldehyde (MDA) plus 4-hydroxyalkenals (4-HDA) production as a reflection of lipid peroxidation. Below 0.6 mM, pinoline inhibited membrane rigidity in a manner parallel to its inhibitory effect on MDA + 4-HDA formation. At concentrations between 1-1.5 mM, pinoline was less effective in stabilizing microsomal membranes than was predicted from its inhibition of lipid peroxidation. The addition of 1 mM melatonin enhanced the membrane-stabilizing activity of pinoline (0.01-0.6 mM). This cooperative effect was not observed for concentrations of pinoline between 1-1.5 mM. When pinoline was tested without induced oxidative damage, 1-1.5 mM pinoline maintained membrane fluidity at the same level as that recorded after induced lipid peroxidation. The results suggest that pinoline may be another pineal molecule that prevents membrane rigidity mediated by lipid peroxidation and this ability is enhanced by melatonin.

Effects of melatonin on the Harderian gland of lipopolysaccharide-treated rats: morphological observations

Melatonin is a free radical scavenger and antioxidant. This indol is reported to efficiently scavenge both hydroxyl and peroxyl radicals and it also reduces both in vitro and in vivo tissue damage due to oxidants which generate oxygen toxic radicals. Lipopolysaccharide (LPS) administration induces oxidative damage in various tissues mainly due to its ability to increase reactive oxygen species. In the present work, we studied the morphological changes and lipid peroxidation in the Harderian gland after LPS administration and the effects of melatonin in preventing the induced changes. Hyperchromasia, vesicular degeneration, necrosis and infiltration with macrophages, monocytes and neutrophils were observed in the LPS-treated group (10 mg/kg, intraperitonally [i.p.]). Also, a typical structure of the glandular acini of the gland exhibited diffuse damage. In the LPS rats treated with melatonin (10 mg/kg, i.p.), a diminished number of infiltrative cells was seen, and cloudy swelling was reduced, as was nuclear hyperchromasia. Neither necrosis nor vesicular degeneration were noted in the melatonin-treated rats, and in general, glandular structure was preserved. Lipid peroxidation products increased significantly within six hours after LPS administration, and melatonin treatment decreased the LPS-dependent lipid peroxidation products. These data together suggest that melatonin protects the Harderian gland against LPS toxicity in terms of morphological damage.