G.B.N. Chainy

Modulation of rat liver mitochondrial antioxidant defence system by thyroid hormone

In the present study the effect of thyroid hormone (T(3)) on oxidative stress parameters of mitochondria of rat liver is reported. Hypothyroidism is induced in male adult rats by giving 0.05% propylthiouracil (PTU) in drinking water for 30 days and in order to know the effect of thyroid hormone, PTU-treated rats were injected with 20 microg T(3)/100 g body weight/day for 3 days. The results of the present study indicate that administration of T(3) to hypothyroid (PTU-treated) rats resulted in significant augmentation of oxidative stress parameters such as thiobarbituric acid reactive substances and protein carbonyl content of mitochondria in comparison to its control and euthyroid rats. The hydrogen peroxide content of the mitochondria of liver increased in hypothyroid rats and was brought to a normal level by T(3) treatment. Induction of hypothyroidism by PTU treatment to rats also resulted in the augmentation of total and CN-sensitive superoxide dismutase (SOD) activities of the mitochondria, which was reduced when hypothyroid rats were challenged with T(3). Although CN-resistant SOD activity of the mitochondria remained unaltered in response to hypothyroidism induced by PTU treatment, its activity decreased when hypothyroid rats were injected with T(3). The catalase activity of the mitochondria decreased significantly by PTU treatment and was restored to normal when PTU-treated rats were given T(3). Total, Se-independent and Se-dependent glutathione peroxidase activities of the mitochondria were increased following PTU treatment and reduced when T(3) was administered to PTU-treated rats. The reduced and oxidised glutathione contents of the mitochondria of liver increased significantly in hypothyroid rats and their level was restored to normal when hypothyroid rats were injected with T(3). The results of the present study suggest that the mitochondrial antioxidant defence system is considerably influenced by the thyroid states of the body.

Testosterone‐induced changes in testicular antioxidant system

Summary. In order to investigate the role of testosterone propionate (TP) on the antioxidant system of the rat testis, lipid peroxidation (LPX) and activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) of the testis of testosterone‐treated and control rats were compared. The results indicate that TP administration to intact adult rats resulted in a significant decline in protein content of various subcellular fractions. This is accompanied with significant elevation in LPX levels of various sub‐cellular fractions suggesting induction of oxidative stress. Activities of three enzymes related to the metabolism of superoxide radical (SOD) and hydrogen peroxide (CAT and GPx) of testis, were found to be significantly decreased in response to TP treatment. The role of testosterone in regulating testicular spermatogenesis through oxidative stress is discussed.

Modulation of antioxidant defences in digestive gland of Perna viridis (L.), on mercury exposures

Sub-lethal effects of mercury exposure (110th of LC(50), i.e. 0.045 mg l(-1)) for 5, 10 and 15 d was investigated on oxidative stress parameters and antioxidant defences in digestive gland of Perna viridis. In addition to this an in vitro effect of mercury single and supplemented with reduced glutathione on lipid peroxidation was studied. Increased lipid peroxidation (during first 10 days and also during in vitro exposures), protein carbonyl and hydrogen peroxides (from 5th till last day of exposure) indicate the resultant oxidative stress in the mercury exposed specimen. DNA damage (F-value) response although less distinct on 5th and 15th d, its low values on 10th d and significant correlation with hydrogen peroxide suggests the toxic role of free radicals towards DNA integrity. Superoxide dismutase, which remains low initially (5th d) and increases later suggests its immediate response against superoxide radical. Higher activities of catalase, glutathione peroxidase and glutathione reductase on 15th d and glutathione-S-tranferase from 10th d onwards suggests the adaptive behaviour of the tissue against oxyradicals. Increasing levels of non-enzymatic antioxidant molecules, such as reduced glutathione and ascorbic acid indicated its involvement in counteracting oxidative damage. Further role of reduced glutathione in reducing Hg toxicity is evident in in vitro experiments where lipid peroxidation remains low in mercury concentrations supplemented with reduced glutathione. The elevated levels of metallothionein from 5th to 10th d suggest involvement of this protein in detoxification of reactive oxygen species and toxic metal. The above results suggest that both enzymatic and non-enzymatic antioxidants play an important role in protecting cell against Hg toxicity, which can be used as a biomarker of metal contamination in aquatic environment.

Antioxidant defenses and oxidative stress parameters in tissues of mud crab (Scylla serrata) with reference to changing salinity

The effects of salinity (10, 17 and 35 ppt) on O(2) consumption, CO(2) release and NH(3) excretion by crabs and oxidative stress parameters and antioxidant defenses of its tissues were reported. An increase in salinity caused a decrease in O(2) consumption and CO(2) release and an increase in ammonia excretion by crabs. Lipid peroxidation, protein carbonyl, H(2)O(2) levels and total antioxidant capacity of the tissues elevated significantly at 35 ppt salinity except in abdominal muscle where H(2)O(2) content was low. Ascorbic acid content of tissues was higher at 17 ppt salinity than at 10 and 35 ppt salinities. With increasing salinity, a gradual decrease in SOD, an increase in catalase, no change in GPx and a decrease followed by an increase in GR activities were recorded for abdominal muscle. While for hepatopancreas, an increase followed by a decrease in SOD and catalase, decrease in GPx and GR activities were noticed with increasing salinity. In the case of gills, a decrease followed by an increase in SOD, a decrease in catalase and GPx and an increase in GR activities were noted when the salinity increased from 10 ppt to 35 ppt. These results suggest that salinity modulation of oxidative stress and antioxidant defenses in Scylla serrata is tissue specific.

Thyroid hormone influences antioxidant defense system in adult rat brain

The objective of the current study was to find out whether thyroid hormone influences antioxidant defense parameters of rat brain. Several oxidative stress and antioxidant defense parameters of mitochondrial (MF) and post-mitochondrial (PMF) fractions of cerebral cortex (CC) of adult rats were compared among euthyroid (control), hypothyroid [6-n-propylthiouracil (PTU)-challenged], and hyperthyroid (T3-treatment to PTU-challenged rats) states. Oxidative stress parameters, such as thiobarbituric acid-reactive substances (TBA-RS) and protein carbonyl content (PC), in MF declined following PTU challenge in comparison to euthyroid rats. On the other hand, when PTU-challenged rats were treated with T3, a significant increase in the level of oxidative stress parameters in MF was recorded. Hydrogen peroxide content of MF as well as PMF of CC was elevated by PTU-challenge and brought to normal level by subsequent treatment of T3. Although mitochondrial glutathione (reduced or oxidized) status did not change following PTU challenge, a significant reduction in oxidized glutathione (GSSG) level was noticed in PMF following the treatment. T3 administration to PTU-challenged rats had no effect on mitochondrial glutathione status. Total and CN-resistant superoxide dismutase (SOD) activities in MF of CC augmented following PTU challenge. CN-resistant SOD activity did not change when PTU-challenged rats were treated with T3. Although CN-sensitive SOD activity of PMF remained unaltered in response to PTU challenge, its activity increased when PTU-challenged rats were treated with T3. Catalase activity in PMF of CC of PTU-challenged rats increased, whereas the activity was decreased when hypothyroid rats were treated with T3. Similarly, total and Se-dependent glutathione peroxidase (GPx) activities of MF increased following PTU challenge and reduced following administration of T3. Se-independent GPx activity of MF and PMF and glutathione reductase activity of PMF decreased following PTU challenge and did not change further when rats were treated with T3. On the other hand, glutathione S-transferase activity of MF and PMF of CC did not change following PTU challenge but decreased below detectable level following T3 treatment. Results of the current investigation suggest that antioxidant defense parameters of adult rat brain are considerably influenced by thyroid states of the body.

Experimentally induced hypo- and hyper-thyroidism influence on the antioxidant defence system in adult rat testis.

The objective of the present experiment was to study the effect of thyroid hormone on the antioxidant defence system of rat testis. Hypothyroidism induced in rats by 6‐n propyl 2‐thiouracil (PTU) treatment resulted in a reduction in body weight, seminal vesicle and ventral prostate gland. A further decrease in the weight of seminal vesicle was recorded following administration of T3 to hypothyroid rats. The oxidative stress parameters such as hydrogen peroxide and protein carbonyl content increased in the crude homogenate of testis of hypothyroid rats. T3 administration to hypothyroid rats resulted in no further change in the hydrogen peroxide level but the protein carbonyl content further elevated in the crude homogenate of testis. No significant change was observed in the endogenous lipid peroxidation level of the crude homogenate of testis whereas the FeSO4/ascorbic acid induced lipid peroxidation level decreased in hypothyroid rats and did not change further by T3 administration. Although the reduced glutathione level in the crude homogenate of testis did not change following hypothyroidism, oxidized glutathione level increased. The reduced and oxidized glutathione level decreased and increased, respectively following T3 administration to hypothyroid rats in comparison with PTU‐treated rats. Activities of superoxide dismutase and catalase decreased in the post‐mitochondrial fraction (PMF) of testis of hypothyroid rats. T3 injection to PTU‐treated rats resulted in an elevation in the level of catalase activity only. The activity of glutathione peroxidase in the PMF of testis elevated in the hypothyroid rats and reduced following T3 treatment to hypothyroid rats. The results of the present study suggest that any alteration in the thyroid hormone level in the body affects the antioxidant defence system of testis of adult rats and, thereby, may affect the physiology of testis through oxidative stress.

Protective effects of vitamin E and curcumin on l-thyroxine-induced rat testicular oxidative stress

Present study examines effects of curcumin and vitamin E on oxidative stress parameters, antioxidant defence enzymes and oxidized (GSSG) and reduced glutathione (GSH) levels in testis of L-thyroxine (T4)-induced hyperthyroid rats. The oxidative stress in T4-treated rat testis was evident from elevation in oxidative stress parameters such as lipid peroxide and protein carbonyl contents, decrease in superoxide dismutase (SOD) and catalase (CAT) activities and increase in glutathione peroxidase (GPx) activity. This is accompanied with decrease in number and mortality of epididymal sperms. When the T4-treated rats were fed with vitamin E and/or curcumin, the lipid peroxide and protein carbonyl contents in crude homogenates of testes decreased to normal level. Treatment of curcumin and/or vitamin E to T4-treated rats resulted in elevation of SOD level in postmitochondrial fraction (PMF) and mitochondrial fraction (MF) and CAT in PMF, with decreased GPx activity in MF. However, curcumin or vitamin E was unable to change GPx activity alone but in together they elevated the GPx in PMF of T4-treated rat testis. Both the antioxidants are incapable of producing significant changes in GSH:GSSG ratio of PMF of T4-treated rats. In MF, GSH:GSSG ratio elevated and decreased respectively by curcumin and vitamin E treatments to T4-treated rats, however, in together these antioxidants caused an elevated GSH:GSSG ratio with a value less than when vitamin E given alone to T4-treated rats. Vitamin E not the curcumin elevates total sperm count and percentage of live sperm impaired by hyperthyroid state. In summary, both vitamin E and curcumin are efficient in protecting testis from oxidative stress generated by T4 mainly in restoring antioxidant enzymes to the level of euthyroid animals up to some extent but vitamin E is more efficient than curcumin.

Alleviation of enhanced oxidative stress and oxygen consumption of L-thyroxine induced hyperthyroid rat liver mitochondria by vitamin E and curcumin.

In the present study, the role of vitamin E and curcumin on hyperthyroidism induced mitochondrial oxygen consumption and oxidative damage to lipids and proteins of rat liver are reported. Adult male rats were rendered hyperthyroid by administration of 0.0012% l-thyroxine in their drinking water, while vitamin E (200 mg/kg body weight) and curcumin (30 mg/kg body weight) were supplemented orally for 30 days. Hyperthyroidism induced elevation in serum aspartate aminotransferase and alanine aminotransferase activities were reduced significantly in response to vitamin E and curcumin treatment. On the other hand, effects of vitamin E and curcumin on hyperthyroidism induced hepatic complexes I and II mediated respiration were found to be different. While curcumin administration ameliorates hyperthyroidism induced state 3 and state 4 respiration in complex I, vitamin E treatment was effective only in reducing state 4 respiration of complex I. On the contrary, curcumin administration was ineffective in modulating hyperthyroidism induced complex II respiration, but vitamin E treatment to hyperthyroid rats resulted in augmentation of complex II respiration both at state 3 and state 4 level. Moreover, vitamin E and curcumin treatment resulted in alleviation of hyperthyroidism induced lipid peroxidation. Enhanced protein carbonylation in hyperthyroid rats is decreased only in response to simultaneous supplementation of vitamin E and curcumin. Above findings suggest that both vitamin E and curcumin have differential regulation on complexes I and II mediated mitochondrial respiration and have a protective role against L-thyroxine induced hepatic dysfunction and oxidative stress.

Dietary vitamin-E modulates antioxidant defence system in giant freshwater prawn, Macrobrachium rosenbergii

The objectives of the present study were to determine the effect of supplementary vitamin-E (200, 400 and 600 mg/kg feed) on lipid peroxidation (LPX) and antioxidant defence system in gills and hepatopancreas of the freshwater prawn, Macrobrachium rosenbergii. Results indicated that vitamin-E inhibited LPX in the hepatopancreas in a comparatively lower dose than gills. Superoxide dismutase (SOD) activity was decreased significantly in gills in response to all the three supplemented diet, but in hepatopancreas decrease was observed only in response to higher doses of vitamin-E (400 and 600 mg/kg feed). Catalase (CAT) activity was reduced significantly only in gills but not in hepatopancreas. While glutathione peroxidase (GPX) activity was significantly elevated in the hepatopancreas by vitamin-E, its activity remains unaltered in gills. On the contrary, glutathione reductase (GR) activity was decreased in gills but that of hepatopancreas was constant. Glutathione (GSH) content of both gills and hepatopancreas was substantially elevated in the vitamin-E supplemented prawns. Although the ascorbic acid (ASA) content of gills was unchanged by vitamin-E, its level elevated significantly in hepatopancreas. Thus the findings of the present investigation suggest that dietary vitamin-E is capable of reducing LPX level and can modulate antioxidant defence system in gills and hepatopancreas, nevertheless, the response is highly tissue specific. It is further observed that highest dose of vitamin-E (600 mg/kg feed) could not render much additional protection in both the tissues.

Comparison of Hexachlorocyclohexane-Induced Oxidative Stress in the Testis of Immature and Adult Rats

1. The acute effect of hexachlorocyclohexane (HCH) administration (i.p.) on testicular antioxidant system and lipid peroxidation (LPX) in immature and mature rats (15- and 90-day-old, respectively) were compared. 2. In both the age groups, the level of LPX in crude homogenate of testis (endogenous, as well as FeSO4, and ascorbic acid-stimulated) was increased after 6 hr of HCH treatment and remained high till 24 hr. However, FeSO4 and ascorbic acid-stimulated LPX was higher in 90-day-old rats in comparison to 15-day-old rats. HCH treatment also resulted in elevation of LPX level in testicular subcellular (nuclear, mitochondrial and microsomal) fractions by 6 hr of treatment. However, the magnitude of increase was greater in case of 90-day-old rats. 3. Activities of testicular cytosolic superoxide dismutases (total and CN(-)-resistant) of rats of 15- and 90-day-old age groups decreased significantly after 6 hr of HCH treatment, and remained decreased till 24 hr of the pesticide treatment. The percentage of decrease was higher in 15-day-old rats than 90-day-old rats. CN(-)-sensitive SOD activity of testis was found to decrease by 12 and 24 hr after the pesticide treatment in 15- and 90-day-old rats, respectively. The activity of catalase decreased 6 hr after the pesticide treatment in both the age groups. However, the magnitude of decrease was similar for both age groups of rats. 4. Testicular glutathione content, as well as levels of glutathione metabolizing enzymes (glutathione peroxidase and glutathione reductase), did not change in response to HCH treatment, whereas ascorbic acid content decreased by 12 and 6 hr after HCH treatment in 15- and 90-day-old rats, respectively. The level of H2O2 was found to be elevated after 6 hr of the pesticide treatment in both age groups. 5. Total epididymal sperm number was comparable in all experimental groups. However, the percentage of dead and damaged spermatozoa was significantly enhanced in HCH treated rats. 6. Acute HCH administration to rats results in induction of oxidative stress in the testis which depends upon the age of the animal.