Green Tea Extract Increases the Expression of Genes Responsible for Regulation of Calcium Balance in Rat Slow-Twitch Muscles under Conditions of Exhausting Exercise.

We studied the role of calcium-regulating structures of slow- (m. soleus, SOL) and fast-twitch (m. extensor digitorum longus, EDL) skeletal muscles of rats during adaptation to exhausting physical activity and the possibility of modulating this adaptation with decaffeinated green tea extract. It was established that EDL adaptation is mainly aimed at Са2+ elimination from the sarcoplasm by Са-ATPase and its retention in the reticulum by calsequestrin. Administration of green tea extract increased endurance due to involvement of slow-twitch muscles whose adaptation is associated with enhanced expression of all the studied genes responsible for the regulation of Ca2+ balance.

Efficacy of green tea extract in two exercise models.

Oral administration of green tea extract in a dose of 6 mg/kg twice a day (before and after exercise) over 2 weeks significantly increased swimming times on week 1 and 2 in comparison with control animals receiving water. The 7-day and final exhaustive running in rats was accompanied by a significant decrease in spleen weight and iron serum levels associated with developed reticulocytosis. Administration of green tea extract in a dose of 12 mg/kg once a day (before exercise) for 2 weeks did not affect the duration of the running, but prevented the decrease in serum iron and spleen weight, that, along with a significantly increased concentration of reduced glutathione in erythrocytes, can indicate a normalizing effect of green tea extract on hemopoiesis and stimulating effect on the antioxidant system of erythrocytes.

Hematological parameters and redox balance of rat blood in the dynamics of immobilization.

Hematological and biochemical parameters were studied in rat blood in the dynamics of immobilization (0.5, 1, and 3 h). Immobilization was followed by a release of old erythrocytes in the circulation and the development of reticulocytosis. The neutrophil count significantly increased by the third hour of immobilization. Restraint stress induced changes in activities of antioxidant enzymes (SOD and catalase) in erythrocytes and plasma level of MDA. The correlation between each enzyme (SOD, glutathione peroxidase, and catalase) and MDA concentration was the highest 1 h after the beginning of immobilization. These data can reflect the tension of antioxidant systems in red blood cells. The biochemical parameters returned to the basal level by the third hour of immobilization. Correlation coefficients between the activities of antioxidant enzymes and MDA amount decreased after 3 h of stress and the correlation between glutathione peroxidase and reduced glutathione significantly increased. The redox status of the blood returned to the initial values after 3 h.

[The effect of antioxidants on erythrocytes in rats during an exhaustive run].

The run of trained rats until exhaustion affected changes of red-ox balance in red blood cells (RBC) and deteriorated the acid stability of RBC. The oral administration of quercetin, 20 mg/kg, caused expansion of oxidative stress in RBC and a significant decrease in RBC acid stability. Pro-oxidant activity of quercetin could contribute accelerated intravascular hemolysis. It was accompanied by a significant reticulocytosis compared with a control group of rats no fed on antioxidant but exposed to run. Green tea extract (GTE) oral administration, 12 mg/kg, resulted in preventing oxidative stress in RBC, increasing in acid stability of RBC and reducing reticulocytosis. Thus, prooxidant activity of quercetin and the high antioxidant efficacy of GTE are indicative of the advantages of the complex preparations containing several antioxidant compounds. Such complex preparations may counteract an oxidative stress and save mechanical stability of erythrocytes under exhausted run.