Influence of a Melatonin Implant on the Free Radical Load In Avian Thydroid and Its Relation With Thyroid Hormonogenesis (original) (raw)
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Biological Rhythm Research, 2016
The aim of this work was to study the variations in the interference of neuroendocrine pineal gland and metabolically active thyroid gland in a tropical bird, Perdicula asiatica. Maximum pineal gland activity (pineal weight and melatonin level), minimum thyroid gland activity (weight, T3/T4 and thymidine kinase activity) along with less oxidative load (MDA level, SOD, CAT and ABTS activity) were observed during reproductively inactive phase (RIP) was observed. Further, a robust and significant rhythmicity was noted in melatonin levels during RIP and RAP, but no significant rhythmicity was noted in T4/T3 level by cosinor analysis. Overall, melatonin and thyroid circadian profile suggested that melatonin might be acting as an antioxidant molecule with time of the day effect in rescuing thyroid gland from free radical load in birds.
Effect of Melatonin on the Response of the Thyroid to Thyrotropin Stimulationin Vitro
General and Comparative Endocrinology, 1997
Thyroidal-melatonin interactions are of particular importance to amphibian development since the thyroid controls the progress of metamorphosis while melatonin may coordinate its rate with prevailing environmental conditions. Melatonin antagonized thyroxine (T 4 ) action at the tissue level and directly inhibited baseline T 4 secretion in culture, so the present work sought to determine if it antagonized the response of the thyroid to thyroid stimulating hormone (TSH) as well. A preliminary experiment showed that, in Rana pipiens, the concentration of TSH (0.2 g/ml) used in the culture of tadpole thyroids stimulated T 4 secretion as much as frog pituitaries, but more than late premetamorphic tadpole pituitaries. There was no significant effect of 1 to 15 g/ml melatonin in TSH-containing thyroid cultures of various Rana species of tadpoles and frogs in experiments with media collected once every 24 or 48 hr, although 15 g/ml melatonin tended to depress T 4 secretion. In a final experiment, a higher melatonin concentration was used as well as more frequent media collections. Thyroids from prometamorphic Rana catesbeiana tadpoles were cultured in L-15 media with periodic stimulation by 0.2 g/ml TSH, or TSH and 10 or 100 g/ml melatonin. Media were collected at the end of two 3-hr TSH pulses, and every 8 hr thereafter for the next 3 days. Melatonin was administered until the end of Day 2 while TSH was given only on Day 2 in addition to the original 3-hr pulses. The secretion of T 4 was inhibited significantly by 10 g/ml melatonin at only two of the early media collections. In contrast, 100 g/ml melatonin significantly depressed T 4 secretion in response to
Melatonin prevents oxidant damage in various tissues of rats with hyperthyroidism
Life Sciences, 2006
Impairment of thyroid functions brings about pathological changes in different organs of body. Findings of in vivo and in vitro studies indicate that thyroid hormones have a considerable impact on oxidative stress. Melatonin reduces oxidative damage through its free radical eliminating and direct anti-oxidant effects. The present study was undertaken to determine how a 3-week period of intraperitoneal melatonin administration affected oxidative damage caused in experimental hyperthyroidism in rat. The experimental animals were divided into 3 groups (control, hyperthyroidism, hyperthyroidism + melatonin). Malondialdehyde (MDA) and glutathione (GSH) levels were determined in different tissues. MDA levels in cerebral, liver and cardiac tissues in hyperthyroidism group were significantly higher than those in control and hyperthyroidism + melatonin supplemented groups (p b 0.001). The highest GSH levels were observed in the group that was administered melatonin in addition to having hyperthyroidism (p b 0.001). These results show that hyperthyroidism increased oxidative damage in cerebral, hepatic and cardiac tissues of rat. Melatonin supplementation may also suppress oxidative damage.
Japanese Journal of Physiology, 2000
Melatonin (N-acetyl-methoxy-tryptamine) was purchased from Sigma and dissolved in absolute ethanol, and later in phosphate-buffered saline (PBS) with a final ethanol concentration of less than 1%. Animals. A total of 24 male Sprague-Dawley rats, age 2 months, were divided into control and melatonin-treated groups. Animals were maintained at 20Ϯ2°C and under 12:12-h light : dark cycle (light from 6:00 a.m. to 6:00 p.m.). After 1 week of acclimation, animals were randomly divided into four groups of six rats each and fed standard pellet food and tap
Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology, 2018
Oxidative damage is a potential physiological cost of thermoregulation during seasonal adjustments to air temperature (T a) in small mammals. Here, we hypothesized that T a affects serum thyroid hormone levels and these hormones can mediate the changes in metabolic rate and oxidative damage. Mongolian gerbils (Meriones unguiculatus) were acclimated at different T a s (5°C, 23°C and 37°C) for 3 weeks. Serum tri-iodothyronine (T3) levels increased at 5°C but decreased at 37°C compared to the control (23°C). Protein carbonyls increased in liver at 37°C compared with control, however, lipid damage (malonaldehyde, MDA) in both serum and liver was unrelated to T a. After the effects of different T a s on thyroid hormone levels and oxidative damage markers were determined, we further investigate whether thyroid hormones mediated metabolic rate and oxidative damage. Another set of gerbils received 0.0036% L-thyroxin (hyperthyroid), 0.04% Methylimazol (hypothyroid) or water (control). Hypothyroid group showed a 34% reduction in resting metabolic rate (RMR) also 42% and 26% increases in MDA and liver protein carbonyl respectively, whereas hyperthyroid group had higher RMR, liver mass and superoxide dismutase (SOD) compared to control. Serum T3 or T3/T4 levels were correlated positively with RMR, liver mass, and SOD, but negatively with MDA and uncoupling protein 2 (UCP2). We concluded that high T a induced hypothyroidism, decreased RMR and increased oxidative damage, whereas low T a induced hyperthyroidism, increased RMR and unchanged oxidative damage. These data supported our hypothesis that thyroid hormones can be a cue to mediate metabolic rate and different aspects of oxidative and antioxidant activities at different T a s.
IOSR Journal of Dental and Medical Sciences, 2014
Antioxidant vitamins neutralize free radicals and may prevent unwanted free radical cellular damage in the body. Free radicals damage other molecules by removing electrons and destroying deoxyribonucleic acid, or DNA.The thyroid gland is an organ of "oxidative nature" as huge amount of ROS, especially of H 2 O 2 , are produced in the thyroid under physiological conditions. Aims-To evaluate the effect of antioxidants on thyroid hormones in rats, fourty wistar were used in this study and with antioxidants namely Vit. C, Vit. E and Turmeric. Methods-The present research work has been undertaken to investigate the free radical scavenging activity and antioxidant status in both hyperthyroid and hypothyroid patients.Adult male Wister rats, weighing around 150-200 gms were used in this research work and under maintained animal care facilities and veterinary supervision. All rats were fed with normal diet (20% protein) and have been administered with known amount of Vitamin C, Vitamin E and turmeric.Results-Samples has been analysed after 15 & 30 days of feeding. Results showed increased levels of thyroxin in rats after 15 days (Vit C-5.2 ± 1.2 NS,Vit E-5.3 ± 0.5 NS and Turmeric-5.3 ± 0.87 NS).Conclusion-It was observed that the circulating levels of T3 were significantly increased in Vit. C, Vit. E and Turmeric extract treated rats (Table-2 and 3). The thyroid hormones responded to antioxydants indicating the significance of antioxydants for the prevention of occurrence of certain diseases in thyroid gland by protecting biological system against potentially harmful effects of processes or reactions that can cause excessive oxidations.
2005
OBJECTIVE: The present study aimed at determining how 3-weeks intraperitoneal melatonin administration affected oxidative stress caused by experimental hyper- thyroidism. MATERIALS AND METHODS: The study was conducted on 30 male rats of Spraque-Dawley species. The experimental animals were divided to 3 groups (control, hyperthyroidism and hyperthyroidism+melatonin). The supplementa- tion was continued for 3 weeks after which the animals were sacrified and tissue malondyaldehyde (MDA) and glutathione (GSH) levels were determined. RESULTS: MDA levels in kidney and testis tissues in hyperthyroidism group were higher than those in control and hyperthyroidism+melatonin administered groups (p<0.001) and levels in hyperthyroidism + melatonin administered group were higher than those in the control group (p<0.001). The highest GSH levels were obtained in hyperthyroidism + melatonin-administered group (p<0.001) and GSH levels in hyperthyroidism group were higher than those in the co...