The therapeutic effects of transferring remote ischemic preconditioning serum in rats with neuropathic pain symptoms.

Background and objectives: Neuropathic pain is defined as pain caused by damage to the nerve as a result of a lesion or disease. It has been shown that ischemic preconditioning exerts a protective role in various tissue injuries; however, the effect of transplantation of remote ischemic preconditioning serum (RIPCs) on neuropathic pain symptoms has not been studied. The aim of this project is to investigate the effect of RIPCs transfusion by different routes of administration on neuropathic pain symptoms. Our secondary aim was to demonstrate the role of Schwann cells in the regeneration of sciatic nerve injury and to evaluate the change in the number of glial cells in the spinal cord dorsal horn. Methods: The sciatic nerve partial ligation method was used to induce neuropathic pain. Changes in neuropathic pain symptoms were assessed by measuring thermal hyperalgesia and mechanical allodynia. To determine the possible therapeutic site, alterations in the number of spinal cord lumbar posterior horn microglia and astrocytes were evaluated by ionized calcium-binding adapter molecule 1 (iba1) and glial fibrillary acidic protein (GFAP) immunostaining. Myelin basic protein immunohistochemistry was also used to assess Schwann cell immunoreactivity in the sciatic nerve. Results: In rats that underwent partial sciatic nerve ligation, neuropathic pain symptoms developed on average on day 12 and persisted up to day 21 (p < 0.0001). RIPCs administered intravenously for five days reduced thermal hyperalgesia more than intraperitoneal and subcutaneous administration (p < 0.05). Both central glial cells appear to play a role in the effect of RIPCs. RIPCs treatment increases Schwann cell remyelination. Conclusions: Our results showed that intravenously administered RIPCs remarkably improved the neuropathic pain symptoms, thermal hyperalgesia and mechanical allodynia. Further studies are needed to evaluate the role of RIPCs transfusion on glial cells.

Anti-Inflammatory and Antipruritic Effects of Remote Ischaemic Postconditioning in a Mouse Model of Experimental Allergic Contact Dermatitis.

Background and Objectives: Allergic contact dermatitis is a common type IV hypersensitivity reaction characterised by redness, itching, oedema and thickening of the skin. It occurs in about 7% of the population and its incidence is increasing. It has been observed that the preconditioning of tissues by exposing them to transient ischemia increases resistance to subsequent permanent ischemia, and this phenomenon is called ischemic preconditioning. It has been shown that conditioning in one organ can also protect other organs. The protective effect of remote ischemic preconditioning is thought to be based on the induction of anti-inflammatory responses. The aim of this project was to investigate the anti-inflammatory and antipruritic effects of remote ischemic postconditioning in a mouse model of experimental allergic contact dermatitis. Methods: Experimental allergic contact dermatitis was induced with 1-fluoro-2,4-dinitrobenzene. Remote ischemic postconditioning was performed at 3 and 25 h after the challenge. Ear thickness and number of scratches 24 and 48 h after challenge, as well as cytokine levels and the infiltration of mast cells, neutrophils, CD4+ and CD8+ T lymphocytes in serum and ear tissue at 48 h were measured to determine the effect of RIPsC. Results: Remote ischemic postconditioning decreased ear thickness, one of the symptoms of allergic contact dermatitis (p < 0.0001). It had no significant effect on the number of scratches. It reduced serum IL-17 levels (p < 0.01). It alleviated local inflammation by suppressing CD8+ T lymphocyte and neutrophil infiltration. Conclusions: It was concluded that remote ischemic postconditioning may alleviate the symptoms of allergic contact dermatitis by suppressing CD8+ T lymphocyte and neutrophil infiltration and reducing IL-17 secretion.

Blood pressure, autonomic stress, and inflammatory markers during sleep deprivation and recovery in healthy men.

OBJECTIVE: Recent community-based studies have identified sleep deprivation (SD) as an important modifiable risk factor for hypertension However, the underlying mechanisms linking SD to hypertension remain elusive. Thus, this study investigates blood pressure (BP) responses to cardiac autonomic stress tests in the presence of SD. Furthermore, we analyzed vascular inflammatory biomarkers as a possible underlying factor linking SD to increased BP. METHODS: Ten healthy male volunteers (age, 21.6±1.2 years) underwent repeated autonomic stress tests for three consecutive days (baseline, SD, and recovery). The autonomic stress tests included the Valsalva maneuver, mental arithmetic, isometric handgrip, and cold pressor tests. Each day, resting BPs were measured, venous blood samples were collected for intercellular adhesion molecule 1, vascular cell adhesion molecule 1, and E-selectin measurements, and stress tests were performed between 0900 and 1100. Ambulatory BP was recorded during the entire SD period (24 h). RESULTS: One-night SD abolished BP reactivity to the Valsalva maneuver, isometric hand grip, and cold pressor tests, which returned after recovery sleep. Ambulatory BP monitoring showed that the mean systolic and diastolic BPs were 121.1±8.5 mm Hg and 72.8±6.3 mm Hg, respectively, between 0700 and 2300 and 120.3±9.6 mm Hg and 74.1±6.1 mm Hg, respectively, between 2300 and 0700 during the SD day (p>0.05 for both). Vascular inflammatory markers seemed unrelated to BP changes. CONCLUSION: Acute SD altered BP responses to cardiac autonomic stress tests in healthy men without affecting resting BP levels. SD led to a non-dipping pattern in BP oscillation. Collectively, these findings highlight the importance of sleep in regulating BP.

Evaluation of the Effects of High Intensity Interval Training on Cytokine Levels and Clinical Course in Treatment of Opioid Use Disorder. / Opioid Kullanim BozukluguTedavisinde Yüksek Yogunluklu Aralikli Egzersizin Sitokin Düzeyleri ve Klinik Seyir Üzerine Etkileri.

OBJECTIVE: Opioid use disorder (OpUD) is a biological and psychosocial disorder with limited treatment options. Addition of physical exercise to the pharmacological treatment has been proposed to be effective on reducing substance use and improving the quality of life. In this study we aimed to investigate the effects of a high-intensity interval training (HIIT) program on the serum levels of cortisol, insulin-like growth factor1 (IGF-1), interferon-gamma (IFN-γ), interleukin 17 (IL-17) and the clinical progress of inpatients with OpUD. METHOD: Our study enrolled 22 male inpatients diagnosed with OpUD on the basis of the DSM-5 criteria. Two groups of 11 individuals were formed as the exercise (EG) and the control (CG) groups. The EG conducted 5 sessions of a HIIT. Participant data were collected with Sociodemographic Questionnaire, the Addiction Profile Index (API), and the Barratt Impulsiveness Scale (BIS-11). Also, the Hamilton Depression Rating Scale (HAM-D), the Hamilton Anxiety Rating Scale (HAM-A) and the Substance Craving Scale (SCS) were used before and after the treatment program in order to evaluate the clinical progress. Blood samples were collected on the 5th and the 21st days for estimation of the serum cortisol, IGF-1, IFN-γ and the IL-17 levels. RESULTS: Comparison of the pre- and the post- treatment performances of the two groups on the HAM-D, the HAM-A and the SCS indicated a significant drop in the respective scores of the EG. Also, a significant increase was observed in the post-treatment IGF-1 level of the EG as compared to the CG. No differences were observed between the cortisol, IFN-γ and IL-17 levels of the EG and the CG. CONCLUSION: HIIT resulted in significant reduction in the symptoms of depression, anxiety and substance craving, and increased the serum IGF-1 levels. HIIT did not change serum cortisol, IFN-γ and IL-17 levels. We believe this research will contribute to the literature on the treatment of opioid depencence by emphasising the effects of HIIT on patients treated for OpUD.

The effects of epidermal growth factor on early burn-wound progression in rats.

After burns, protecting tissues by medicines in the zone of stasis reduces the width and depth of injury. This study's goal was to reduce burned tissue damage in the zone of stasis using epidermal growth factor (EGF). Forty-eight Wistar rats were separated into three groups. In all groups, the burn procedure was applied following the comb burn model. In Group 1, no postburn treatment was administered. In Group 2, physiological saline solution (0.3 cc) was injected intradermally and in Group 3, EGF (0.3 cc) was injected intradermally into stasis zone tissues after the burn procedure. Surviving tissue rates were 24.0% in Group 1, 25.3% in Group 2, and 70.2% in Group 3. The average numbers of cells stained with Nrf2, HO-1, and the number of apoptotic cells were 230, 150, and 17.5 in Group 1, 230, 145, and 15.0 in Group 2, and 370, 230, and 0 in Group 3, respectively. Values in Group 3 were found to be statistically significantly different than those of Groups 1 and 2; there was no difference between Groups 1 and 2. This study shows that EGF protects zone of stasis tissue from burn damage.

Effects of cannabinoid modulation on hypothalamic nesfatin-1 and insulin resistance.

Both nesfatin-1 and cannabinoid systems involved in the regulation of sleep, metabolism, and food intake. The relationship between cannabinoid system and nesfatin-1 levels remains to be elucidated. This study investigated nesfatin-1 and insulin resistance in 72-h rapid eye movement (REM) sleep-deprived mice under the effects of cannabinoid, and cannabinoid receptors CB1R and CB2R blocking. Sixty mice were exposed to 72-h sleep deprivation. Groups and drug administrations were as follows: Group 1 (control) received injection of vehicle. Group 2 received WIN 55,212,2. Group 3 received AM251 (CB1R antagonist) followed by WIN 55,212,2 injection. Group 4 received SR144528 (CB2R antagonist) followed by WIN 55,212,2 injection. Group 5 received only AM251. Group 6 received only SR144528. Blood samples were collected 1 h after drug administration and prepared for biochemical measurements. Glucose levels were measured by glucometer, whereas insulin and nesfatin-1 levels were measured by ELISA. Central nesfatin-1 was also assessed using immunohistochemistry. One-way analysis of variance together with post hoc Tukey's test was used for inter-group comparisons. Serum nesfatin-1 levels were comparable in all study groups. Brain nesfatin-1 immune-positive cell count was lower in WIN group compared to controls. The administration of CB1R or CB2R antagonist prevented reduction in nesfatin-1-positive cell count. Insulin resistance was higher in WINCB2 and CB2 groups than in control and WINCB1 groups. Cannabinoid treatment reduced nesfatin-1 immunoreactivity in the central nervous system and this effect was prevented by either CB1R or CB2R antagonist pretreatment. Insulin resistance might be related to CB2 receptor activation which was independent from central nesfatin-1 immunoreactivity.

The Effects of Irisin on Nω-Nitro-L-arginine Methyl Ester Hydrochloride-Induced Hypertension in Rats

Background: The cause of about 95% of hypertension, an important public health problem, is unknown. Intensive studies are underway to understand the physiopathology of hypertension. Irisin, a newly discovered hormone, has been reported to dilate vascular smooth muscle and lower blood pressure acutely. Aims: To investigate the effects of chronic irisin treatment on blood pressure and renal functions in a hypertension model established by nitric oxide synthase inhibition by treatment with Nω-nitro-L-arginine methyl ester hydrochloride. Study Design: Animal experimentation. Methods: Male Sprague−Dawley rats were divided into four groups (n=8). Control and irisin groups received an intravenous saline injection, hypertension and hypertension + irisin (hypertension + irisin) groups received 1.5 mg/100 g Nω-nitro-L-arginine methyl ester hydrochloride. Nω-nitro-L-arginine methyl ester hydrochloride (150 mg/L) was added to the drinking water of rats in groups hypertension and hypertension + irisin for three weeks. In the second week of the experiment, irisin (50 nmol/day) was given to rats in groups irisin and hypertension + irisin, and saline was administered to rats in groups control and hypertension for two weeks through subcutaneously placed osmotic minipumps. Blood pressure was measured by the tail-cuff plethysmography method. On the twenty-first day of the experiment, 24-hour urine, blood, and both kidneys of the rats were collected. Results: The hypertension group had elevated systolic, diastolic, and mean arterial blood pressure values compared with the control group, with decreased glutathione levels in tissue and serum, but an increase in serum oxidized glutathione level (p<0.05). Histopathologically, increased tubular injury, cast formation, glomerular sclerosis, and peritubular fibrosis levels were observed (p<0.05). Irisin treatment did not cause any significant change in blood pressure, renal functions, and injury scores. However, renal nitric oxide levels significantly increased, and endothelial nitric oxide synthase immunoreactivity was determined to be reduced (p<0.05). Conclusion: Treatment with chronic irisin at a physiological dose does not reduce blood pressure in an experimental model of hypertension. In different models of experimental hypertension, the effects of irisin administration at different doses and at different periods should be thoroughly investigated.

The effect of platelet-rich plasma in inactive form on the burn zone of stasis in rats.

The protection of the burn stasis zone tissues (BSZT) reduces the width and depth of the burn injury. In this study, it is aimed to show the effect of platelet-rich plasma (PRP) on the burn zone of stasis. Seventy-two Wistar rats were used in the study. PRP was obtained from the blood taken from eight rats. The remaining 64 rats were divided into four groups. In Group 1, only the burn procedure was performed. In Group 2, 0.3 cc of physiological saline solution, in Group 3, 0.3 cc of platelet-poor plasma and in Group 4, 0.3 cc of PRP were intradermally injected into BSZT after burn procedure. 21.5% of the tissues in Group 1, 20.8% in Group 2, 27.0% in Group 3, and 69.6% in Group 4 were found to be alive. The autophagic cell number average was calculated as 340 in Group 1, 340 in Group 2, 335 in Group 3 and 450 in Group 4, while the average number of cells stained with Nrf2 was calculated as 225 in Group 1, 245 in Group 2, 250 in Group 3 and 370 in Group 4. When the groups were compared in terms of the living tissue ratio, autophagy and number of cells stained with Nrf2, the values in Group 4 were found to be statistically significantly higher compared to Group 1, Group 2 and Group 3, while there was no difference between Groups 1, 2 and 3. This study has shown that PRP has a protective effect on BSZT.

Transferring the protective effect of remote ischemic preconditioning on skin flap among rats by blood serum.

The aim of this study was to show whether the protective effect of remote ischemic preconditioning (RIPC) on flaps can be transferred among different individuals with the transfusion of blood serum. Blood serum was taken from rats without any procedure (Group x), rats 1 hour (Group y) and 24 hours (Group z) after performing RIPC and the remaining rats were divided into six groups. While the random pattern skin flap was performed only in the back region in Group 1, and it was performed 1 hour (Group 2) and 24 hours (Group 3) after induction RIPC. Flap surgery was performed after the intravenous injection of serum obtained from Group x in Group 4, from Group y in Group 5, and from Group z in Group 6. After 7 days, the ratios of viable areas in the flaps of the remaining rats were calculated. When the viable area ratios in the flaps to the whole flap area were calculated, it was found out that the viable area ratios in Group 2 (61.6%), Group 3 (75.6%) and Group 6 (74.2%) were statistically significantly higher compared to Group 1 (51.5%), Group 4 (52.6%) and Group 5 (58.7%), that viable area ratios in Groups 3 and 6 were statistically significantly higher compared to Group 2, and that there was no difference between Groups 3 and 6. This study showed that RIPC forms a protective effect on the flaps and that this effect could be transferred among individuals with blood serum.

Effect of a four-week exercise program on the secretion of IFN-γ, TNF-α, IL-2 and IL-6 cytokines in elite Taekwondo athletes.

The aim of the present study was to examine how a 4-week exercise program affects the serum levels of certain cytokines in Taekwondo athletes. The study involved 10 elite male Taekwondo athletes (mean age, 20.67±0.24 years; mean weight, 65.45±1.69 kg) who were studying at the Physical Education and Sports High School of Selçuk University (Konya, Turkey) in June 2014. The subjects were involved in a Taekwondo exercise program on every weekday for 4 weeks. The subjects were also engaged in an exercise to exhaustion session twice; once before starting the 4-week exercise program and once upon completion of the program. Blood samples were collected from the subjects in four rounds: During rest, upon fatigue, and before and after the 4-week exercise program. These samples were analyzed to establish the serum levels of interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), interleukin (IL)-2 and IL-6 using enzyme-linked immunosorbent assay test kits. Pre- and post-exercise program, the IFN-γ and TNF-α levels did not show any significant difference. When compared with the pre-exercise levels, serum IL-2 levels of the subjects were found to be elevated after the 4-week exercise program. The highest serum IL-6 values were established after the subjects were exercised to fatigue before the exercise program was initiated (P<0.05). The 4-week exercise program resulted in a decrease in IL-6 levels (P<0.05). The findings of the study indicate that a 4-week exercise program did not result in significant changes in IFN-γ and TNF-α levels, but led to an increase in IL-2 levels. The notable finding of the present study is that a 4-week exercise program reduces cellular immune functions and, thus, the levels of IL-6, which negatively influences performance.

A new biflavonoid from Solanum dulcamara L. and investigation of anti-hyperglycaemic activity of its fruit extract.

A new biflavone, 6,2',3″,5″,4‴-pentahydroxy-3,7″-biflavone, has been isolated from the fruits of Solanum dulcamara L., in addition to two known compounds, ß-sitosterol and stigmasterol. Their structures were established on the basis of UV, IR, 1D, 2D NMR and HR-ESI-MS spectroscopic methods. The anti-hyperglycaemic effect of S. dulcamara was investigated using diabetic rats. The anti-hyperglycaemic activity of the fruit extract of S. dulcamara was presented for the first time in this study.

The alteration of asymmetric dimetilarginine (ADMA) levels in cardiac and gastrocnemius muscles following radioactive iodine application in guinea pigs and the effect of L-carnitine on this alteration.

PURPOSE: Tissue levels of asymmetric dimetilarginine (ADMA) and symmetric dimetilarginine (SDMA) were investigated in cardiac ventricle and gastrocnemius muscles of guinea pigs treated with radioactive iodine (RAI) alone or in combination with L-carnitine (LC). MATERIAL AND METHODS: Group 1 received no treatment (control group). Group 2 received a total dose of 30 mCi⁻¹kg⁻¹ body weight iodine-131 alone. Group 3 received 200 mg⁻¹kg⁻¹ of LC for 10 days alone. Group 4 received 200 mg⁻¹kg⁻¹ of LC plus RAI therapy. Free thyroid hormones, ADMA and SDMA concentrations were measured. RESULTS: Serum free thyroid hormone concentrations were found decreased in the RAI and LC-RAI groups after RAI application. A significant decrease in ADMA and SDMA concentration was observed in ventricle muscle following RAI application. The LC-RAI group had significantly decreased ADMA levels in ventricle muscle compared with those of the control group. Similarly, SDMA concentrations in ventricle and gastrocnemius muscles of the LC-RAI groups were significantly lower than those of the control groups. CONCLUSIONS: Our results indicated that RAI appears to exert an inhibitory effect on ADMA and SDMA levels of ventricular muscle. LC administration when given adjuvant to RAI therapy may cause a marked decrease in ADMA concentrations of both ventricular and gastrocnemius muscles.

Effect of melatonin supplementation on plasma glucose and liver glycogen levels in rats subjected to acute swimming exercise.

The aim of the present study is to examine how melatonin supplementation affects plasma glucose and liver glycogen levels in rats subjected to acute swimming exercise. Sprague-Dawley species thirty adult male rats were allocated to 3 groups with equal number of animals: general control group which was not subjected to any procedure (Group 1), the group subjected to a 30-minute acute swimming exercise (Group 2), and the group subjected to a 30-minute acute swimming exercise after intraperitoneal (i.p.) melatonin supplementation (3 mg/kg/day) for 4 weeks (Group 3). Blood samples collected from the experimental animals by decapitation method were analyzed in terms of plasma glucose, and glycogen levels were determined in liver tissue samples by histological method. The highest plasma glucose levels were obtained in group 2 (p < 0.05). Plasma glucose levels in groups 1 and 3 were not different. Mean liver glycogen level in group 3 was significantly higher than those in the other groups (p < 0.01), while there was no significant difference between group 1 and group 2 in terms of this parameter. Results of the study demonstrate that melatonin supplementation can have a protective effect on liver glycogen reserves in rats subjected to acute swimming exercise.

Effect of acute swimming exercise on lactate levels and its relation with zinc in pinealectomized rats.

It is argued that melatonin secreted from the pineal gland regulates the levels of zinc, which is an important trace element. Decreases in zinc levels of pinealectomized rats supports this relationship. There is an increasing amount of evidence suggesting that the pineal gland can have important effects on physical activity. The objective of the present study was to explore the changes in serum lactate levels in pinealectomized rats subjected to acute swimming exercise and its relation with zinc. Forty adult male rats of Spraque Dawley strain were equally allocated to four groups. Group 1: General Control Group. Group 2: Pinealectomized Control Group. Group 3: Swimming Control Group. Group 4: Pinealectomized Swimming Group. Serum zinc, melatonin and lactate levels were determined in the blood samples collected from the animals by a decapitation method. Zinc and melatonin levels were higher in Group 1 than in Groups 2, 3 and 4 (p < 0.01), higher in Group 3 than in Groups 2 and 4 (p < 0.01) and higher in Group 2 than in Group 4 (p < 0.01). The highest lactate levels were found in Group 4 (p < 0.01). Lactate levels in Group 3 were higher than those in Groups 1 and 2 (p < 0.01), while the levels in Groups 1 and 2 did not differ. Pinealectomy results in a significant increase in lactate levels in rats subjected to an acute swimming exercise. This increase in lactate levels may be associated with the decrease observed in zinc levels after pinealectomy.

The relationship between body composition and anaerobic performance of elite young wrestlers.

UNLABELLED: The purpose of the present study was to investigate the relationship between body composition and anaerobic performance in young elite wrestlers. METHOD: Eight female (age = 16.2 ± 1.1 yrs) and 8 male (age = 17.3 ± 0.9 yrs) wrestlers from the Turkish cadet and junior national team participated in this study. Fat free mass (FFM) and percent fat mass (%FM) were carried out through electric bioimpedance. Anaerobic performance was assessed by the Wingate test (load was calculated as 0.090 kg x.kg(-1) body mass). FFM was greater in male wrestlers [65.4 ± 12.3 (kg)] than female wrestlers (45.1 ± 4.6 (kg) p < 0.01). %FM was lower in male wrestlers (9.7 ± 6.3) than female wrestlers (18.5 ± 2.8; p < 0.01). Peak power was significantly higher in male wrestlers than female wrestlers (8.5 ± 1.0 W·kg(-1) vs. 6.8 ± 0.6 W·kg(-1); p < 0.01). Mean power was significantly correlated with FFM in both genders (r = 0.73 p < 0.05 in female; r= 0.90 p < 0.05 in male). No relationship was obtained between anaerobic parameters and %FM. In conclusion, our result demonstrated no association between anaerobic parameters and %FM. Wrestlers and their coaches should take into account FFM rather than %FM for higher anaerobic performance. Key pointsMean power and fat free mass association was obtained from both genders.Anaerobic performance parameters obtained from Wingate Test were positively associated with fat free mass but not % fat mass in elite young wrestlers.% FM values were 18.5 in young female wrestlers, and it was 9.7 in male wrestlers.

Zinc supplementation in rats subjected to acute swimming exercise: Its effect on testosterone levels and relation with lactate.

OBJECTIVE: There is fairly scarce information about the effects of zinc, an essential trace element, on performance. Studies concerned with the relation between zinc and exercise mostly concentrate on the distribution of this element in the body in response to exercise. The objective of the present study is to explore how zinc supplementation affects testosterone levels and its relation with lactate in rats subjected to acute swimming exercise. MATERIALS AND METHODS: Thirty adult male rats of Sprague-Dawley species were equally allocated to 3 groups. Group 1: Control. Group 2: Group subjected to 30-minute acute swimming exercise. Group 3: Group supplemented with intraperitoneal (i.p.) zinc (3 mg/kg day) for 4 weeks and subjected to 30-minute swimming exercise. Blood samples collected from all experimental animals by decapitation method were analyzed to determine free and total testosterone and lactate levels in the plasma. RESULTS: Group 3 had the highest free and total testosterone levels, followed by Group 1 and Group 2. The highest lactate levels were found in Group 2 and the levels in Group 3 were higher than those in Group 1. CONCLUSION: Results of the study demonstrate that zinc supplementation leads to a significant increase in testosterone levels and a significant decrease in lactate levels. In conclusion, physiological doses of zinc supplementation can be useful for performance.

Melatonin supplementation to rats subjected to acute swimming exercise: Its effect on plasma lactate levels and relation with zinc.

OBJECTIVE: The objective of the present study is to examine the effect on melatonin supplementation on plasma lactate levels and its relation with zinc in rats subjected to acute swimming exercise. METHODS: Thirty adult male rats of Spraque-Dawley species were allocated to 3 groups, each containing an equal number of rats: general control group which was not subjected to any procedure (Group 1), the group which was subjected to 30 minutes acute swimming exercise (Group 2), and the group which was subjected to 30 minutes acute swimming exercise after 4-week intraperitoneal (i.p.) melatonin (3 mg/kg/day) supplementation. Lactate and zinc levels in the plasma were studied in the blood samples taken from the experimental animals by decapitation method. RESULTS: The animals in the control group, which was not subjected to any procedure (group 1), had higher lactate levels than those in groups 2 and 3 (p<0,05). Lactate levels in the swimming group supplemented with melatonin (group 3) were lower than those in group 2 (swimming group) (p<0,05). The highest plasma zinc levels were obtained in the melatonin-supplemented swimming group (group 3) (p<0,05). Group 2 (swimming control) had the lowest plasma zinc levels (p<0,05). CONCLUSION: Results of the study demonstrate that melatonin supplementation to rats subjected to acute swimming exercise reduces lactate levels, thereby delaying exhaustion. Increased zinc levels may be mediating this melatonin effect.