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PubMed1998

[Chemoprotection by green tea against the formation of food-borne carcinogen 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP)-DNA adducts in rats].

OBJECTIVE: The food-borne mutagen 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP) induces colon and mammary gland tumors in rats and has been implicated in the etiology of human cancer, particularly colorectal cancer. This study was conducted to examine the potential chemopreventive effect of Chinese green tea against PhIP-DNA adduct formation in rats and its possible mechanisms. METHODS: Sprague-Dawley rats were maintained on freshly prepared aqueous extract of Chinese green tea (3%) or tap water as the sole source of drinking fluid for 10 days prior to administration with a single dose of PhIP (10 mg/kg body wt) by oral gavage. Rats were sacrificed at 20 h after PhIP treatment and PhIP-DNA adducts in the colon, heart, lung, and liver were analyzed using 32P-postlabeling technique. The activity of cytosolic glutathione S-transferases (GSTs) in the liver, lung and colon mucosa was also determined using CDNB as substrate. RESULTS: The levels of PhIP-DNA adducts in the four tissues of rats treated with PhIP alone were highest in the colon (53 +/- 9 adducts/10(8) nucleotides), followed by heart (41 +/- 14 adducts/10(8) nucleotides) and lung (22 +/- 5 adducts/10(8) nucleotides), but much lower in the liver (5 +/- 3 adducts/10(8) nucleotides). Rats pre-treated with green tea had significantly reduced levels of PhIP-DNA adducts, with the inhibition rates being 59%-80%, respectively. While the organ distribution profile of the adducts was not altered by tea treatment as compared with controls given PhIP alone. The GST activity towards CDNB in hepatic, colonic and lung cytosols appear not to be modified by drinking green tea. CONCLUSION: These results support a protective role for green tea against PhIP-initiated carcinogenesis in rats and suggest that consumption of green tea may have significant impact in chemoprevontion against human cancer presumably related to PhIP and other heterocyclie amines.

Animals↗
PubMed1995

Chemopreventive effect of green tea (Camellia sinensis) among cigarette smokers.

Chemopreventive effects of green tea and coffee among cigarette smokers were examined in 52 clinically healthy male subjects between 20 and 52 years of age. Blood specimens were obtained from nonsmokers (group I), smokers (group II), smokers consuming green tea (group III), and smokers drinking coffee (group IV). The mean number of cigarette smoking years (> 10 cigarettes/day) in groups II-IV ranged from 13.4 to 14.7 years. Daily intake of green tea and coffee was 2-3 cups/day for 6 months (groups III and IV). The frequencies of sisterchromatid exchange (SCE) in mitogen-stimulated peripheral lymphocytes from each experimental group were determined and analyzed statistically. SCE rates were elevated significantly in smokers (9.46 +/- 0.46) versus nonsmokers (7.03 +/- 0.33); however, the frequency of SCE in smokers who consumed green tea (7.94 +/- 0.31) was comparable to that of nonsmokers, implying that green tea can block the cigarette-induced increase in SCE frequency. Coffee, in contrast, did not exhibit a significant inhibitory effect on smoking-induced SCE.

Adult↗
PubMed1992

A multi-institute case-control study on the risk factors of developing pancreatic cancer.

A multi-institute, hospital-based, case-control study on pancreatic cancer was carried out to examine its association with preceding diseases, cigarette smoking, alcohol drinking and dietary factors. Analyses were based on 124 newly diagnosed exocrine pancreatic cancer cases and sex-, age- and institute-matched hospital controls in seven hospitals in Japan. Cigarette smoking showed a positive association with the risk of developing pancreatic cancer. Especially among smokers, a risk enhancing effect of involuntary/passive smoking prior to twenty years of age was observed (P < 0.05). No consistent associations were found with coffee, black tea or alcohol consumption. Among dietary factors, favoring food of a salty taste and drinking green tea five cups per day or more were positively associated with the risk. Drinking milk and eating fish everyday were inversely associated with the risk.

Adult↗
PubMed1989

[The role of tea consumption in dental fluorosis in Jordan].

2,516 children of both sexes, six to fourteen years old, were examined in Jordan in the course of an epidemiological study. 81.11% of girls and 76.43% of boys presented severe forms of dental fluorosis according to DEAN's index. Drinking water analysis revealed fluoride concentrations ranging from 0.27 to 1.4 mg F/l. These concentrations are neighbouring optimum tolerated fluoride supplementation in drinking water. However high annual temperature mean and ten hours daily sunshine must also be taken in consideration. For social and climatic reasons, Jordanian children drink daily high quantities of tea. Analysis of tea prepared on jordanian way revealed a concentration of 1.2 mg F/l. This continuous intake of fluoride might explain the high severity of dental fluorosis in Jordan.

Adolescent↗
PubMed1994

Inhibitory effects of black tea, green tea, decaffeinated black tea, and decaffeinated green tea on ultraviolet B light-induced skin carcinogenesis in 7,12-dimethylbenz[a]anthracene-initiated SKH-1 mice.

In a previous study (Z. Y. Wang et al., Cancer Res., 52: 1162-1170, 1992), we found that administration of a water extract of green tea leaves as the sole source of drinking fluid inhibited ultraviolet B light (UVB)-induced carcinogenesis in SKH-1 mice previously initiated with 7,12-dimethylbenz[a]anthracene (DMBA). In the present study, we compared the effects of black tea, green tea, decaffeinated black tea, and decaffeinated green tea on UVB-induced skin carcinogenesis in DMBA-initiated SKH-1 mice. A 1.25% water extract of each kind of tea leaf (1.25 g tea leaf/100 ml water) was prepared by passing 4 liters of hot water through 50 g of tea leaves in a Bunn tea brewing machine. The mean concentrations of solids in multiple samples of 1.25% black tea, green tea, decaffeinated black tea, and decaffeinated green tea analyzed during the course of this study were 4.23, 3.94, 3.66, and 3.53 mg/ml, respectively. These concentrations of tea solids are similar to those present in tea brews ingested by humans. Female SKH-1 mice were treated topically with 200 nmol of DMBA, followed 3 weeks later by irradiation with 30 mJ/cm2 of UVB twice weekly for 31 weeks. UVB-induced formation of skin tumors was markedly inhibited by oral administration of 0.63 or 1.25% black tea, green tea, decaffeinated black tea, or decaffeinated green tea as the sole source of drinking fluid 2 weeks prior to and during 31 weeks of UVB treatment. Administration of each of the eight tea preparations not only inhibited the number of tumors, but tumor size was also markedly decreased. Histopathological examination of each tumor showed that oral administration of the eight tea preparations had a marked inhibitory effect on the formation of UVB-induced keratoacanthomas and carcinomas. Administration of 1.25% black tea, green tea, decaffeinated black tea, or decaffeinated green tea inhibited the number of keratoacanthomas per mouse by 79, 78, 73, or 70%, respectively, and the number of carcinomas per mouse was inhibited by 93, 88, 77, or 72%, respectively. In summary, administration of black tea was comparable to green tea as an inhibitor of UVB-induced skin carcinogenesis in DMBA-initiated SKH-1 mice. Oral administration of decaffeinated black tea or decaffeinated green tea also had a marked inhibitory effect on UVB-induced skin carcinogenesis in DMBA-initiated SKH-1 mice, but these tea preparations were slightly less effective than the regular teas at the high dose level.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2000

Plasma and tissue levels of tea catechins in rats and mice during chronic consumption of green tea polyphenols.

To understand the relationship between tea consumption and its biological effects, plasma and tissue levels of (-)-epigallocatechin-3-gallate (EGCG), (-)-epigallocatechin (EGC), and (-)-epicatechin (EC) were measured after rats and mice were given a 0.6% green tea polyphenol preparation as the drinking fluid for different periods of time. EGC and EC levels in rat plasma increased over time and reached peak values (3 times the Day 1 values) on Day 14. Then the plasma levels of tea catechins decreased, to Day 1 values on Day 28. The plasma concentrations of EGCG were much lower than those of EGC or EC. High levels of EGC and EC were found in urine, whereas high levels of EGCG were found in feces. The changes in the urinary and fecal excretions of tea catechins could not account for the above-described changes in the plasma levels. The amounts of catechins in different tissues reflected the ingestion, absorption, and excretion pattern. When the green tea polyphenol preparation was given to mice, the "increase-and-then-decrease" pattern of catechin levels was also observed in the plasma, lung, and liver; the EGCG levels were much higher than in the rats. The results suggest that consumption of tea by rodents could induce adaptive responses affecting blood and tissue levels of tea catechins with time and that investigation of a similar phenomenon in humans is warranted.

Adaptation, Biological↗
PubMed1997

Toxicology of mono-, di-, and triethanolamine.

The chemistry, biochemistry, toxicity, and industrial use of monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA) are reviewed. The dual function groups, amino and hydroxyl, make them useful in cutting fluids and as intermediates in the production of surfactants, soaps, salts, corrosion control inhibitors, and in pharmaceutical and miscellaneous applications. In 1995, the annual U.S. production capacity for ethanolamines was 447,727 metric tons. The principal route of exposure is through skin, with some exposure occurring by inhalation of vapor and aerosols. MEA, DEA, and TEA in water penetrate rat skin at the rate of 2.9 x 10(-3), 4.36 x 10(-3) and 18 x 10(-3) cm/hr, respectively. MEA, DEA, and TEA are water-soluble ammonia derivatives, with pHs of 9-11 in water and pHa values of 9.3, 8.8, and 7.7, respectively. They are irritating to the skin, eyes, and respiratory tract, with MEA being the worst irritant, followed by DEA and TEA. The acute oral LD50s are 2.74 g/kg for MEA, 1.82 g/kg for DEA, and 2.34 g/kg for TEA (of bw), with most deaths occurring within 4 d of administration. MEA is present in nature as a nitrogenous base in phospholipids. These lipids, composed of glycerol, two fatty acid esters, phosphoric acid, and MEA, are the building blocks of biomembranes in animals. MEA is methylated to form choline, another important nitrogenous base in phospholipids and an essential vitamin. The rat dietary choline requirement is 10 mg kg-1 d-1; 30-d oral administration of MEA (160-2670 mg kg-1 d-1) to rats produced "altered" liver and kidney weights in animals ingesting 640 mg kg-1 d-1 or greater. Death occurred at dosages of 1280 mg kg-1 d-1. No treatment-related effects were noted in dogs administered as much as 22 mg kg-1 d-1 for 2 yr. DEA is not metabolized or readily eliminated from the liver or kidneys. At high tissue concentrations, DEA substitutes for MEA in phospholipids and is methylated to form phospholipids composed of N-methyl and N, N-dimethyl DEA. Dietary intake of DEA by rats for 13 wk at levels greater than 90 mg kg-1 d-1 resulted in degenerative changes in renal tubular epithelial cells and fatty degeneration of the liver. Similar effects were noted in drinking water studies. The findings are believed to be due to alterations in the structure and function of biomembranes brought about by the incorporation of DEA and methylated DEA in headgroups. TEA is not metabolized in the liver or incorporated into phospholipids. TEA, however, is readily eliminated in urine. Repeated oral administration to rats (7 d/wk, 24 wk) at dose levels up to and including 1600 mg kg-1 d-1 produced histopathological changes restricted to kidney and liver. Lesions in the liver consisted of cloudy swelling and occasional fatty changes, while cloudy swelling of the convoluted tubules and loop of Henle were observed in kidneys. Chronic administration (2 yr) of TEA in drinking water (0, 1%, or 2% w/v; 525 and 1100 mg kg-1 d-1 in males and 910 and 1970 mg kg-1 d-1 in females) depressed body and kidney weights in F-344 rats. Histopathological findings consisted of an "acceleration of so-called chronic nephropathy" commonly found in the kidneys of aging F-344 rats. In B6C3F1 mice, chronic administration of TEA in drinking water (0, 1%, or 2%) produced no significant change in terminal body weights between treated and control animals or gross pathological changes. TEA was not considered to be carcinogenic. Systemic effects in rats chronically administered TEA dermally (0, 32, 64, or 125 mg kg-1 d-1 in males; 0, 63, 125, or 250 mg kg-1 d-1 in females) 5 d/wk for 2 yr were primarily limited to hyperplasia of renal tubular epithelium and small microscopic adenomas. In a companion mouse dermal study, the most significant change was associated with nonneoplastic changes in livers of male mice consistent with chronic bacterial hepatitis.

Animals↗
PubMed2003

Effects of green tea and high-fat diet on arachidonic acid metabolism and aberrant crypt foci formation in an azoxymethane-induced colon carcinogenesis mouse model.

Excessive fat consumption is a risk factor for colon carcinogenesis, and green tea consumption may reduce the risk of colon and other cancers. The current study was designed to investigate the effects of green tea and a high-fat diet on arachidonic acid metabolism and aberrant crypt foci formation in an azoxymethane (AOM)-induced colon carcinogenesis mouse model. We also determined whether green tea consumption altered the size of regional fat pads. CF-1 female mice were maintained on either a high-fat (20% corn oil) or a low-fat (5% corn oil) diet. AOM was given subcutaneous at a dose of 7.5 mg/kg body weight at 6 wk and then a dose of 10 mg/kg at 7 wk of age. Two weeks after the second AOM injection, 0.6% green tea (6 mg tea solids/ml) was given as the drinking fluid and continued for 10 wk until the experiment was terminated. In the AOM-treated mice not receiving green tea, the high-fat diet significantly enhanced colonic levels of 5-lipoxygenase, leukotriene A4 hydrolase, and leukotriene B4, but it did not significantly alter prostaglandin E2 levels and aberrant crypt foci formation. In AOM-treated mice on the high-fat diet, green tea significantly decreased colonic levels of cytosolic phospholipase A2, 5-lipoxygenase, and leukotriene B4; green tea treatment also decreased the number of aberrant crypt foci (P < 0.05). The weights of parametrial and retroperitoneal fat pads were increased by the high-fat diet and decreased by green tea treatment. The current results indicate that green tea consumption and dietary fat modulate 5-lipoxygenase-dependent pathway of arachidonic acid metabolism during AOM-induced colon carcinogenesis. Green tea inhibits ACF formation in mice on a high corn oil diet, suggesting its possible inhibitory effect on colon carcinogenesis in populations such as those in Western countries that consume high amounts of fat.

Adipose Tissue↗
PubMed2003

Tonic in a teapot.

Here's the latest evidence tea is good for you and, because you have to drink it to reap the benefits, our taste tests of 19 green teas.

Antioxidants↗
PubMed2006

Trace element level in infant hair and diet, and in the local environment of the Moroccan city of Marrakech.

A sample of 573 infants (aged 0 to 12 months) from the Moroccan city of Marrakech was studied in order to determine the level of Pb and Al contaminations. Mean values of Pb and Al in children's hair were 6.6 and 9.5 microg/l, respectively. Age, gender, and parents' occupation influenced significantly Pb content but not Al content. Larger mean values were measured for Al compared with Pb. This finding can be explained by a higher level of Al available in both the infant diet (complementary feeding) and the local environmental factors (soil and drinking water). During weaning, beverages like tea, widely used in Morocco, represent an important source of Pb and Al contamination. Al content in drinking water is above the international standard.

Aluminum↗
PubMed2000

Tea as a potential chemopreventive agent in PhIP carcinogenesis: effects of green tea and black tea on PhIP-DNA adduct formation in female F-344 rats.

The heterocyclic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is formed during the cooking of proteinaceous animal foods (meat, chicken, and fish). PhIP is a carcinogen in the Fischer 344 (F-344) rat; it induces mammary tumors in female rats and lymphomas and colon and prostate tumors in male rats. In F-344 rats, PhIP forms DNA adducts in various organs, including the target organs. Inhibition of PhIP-DNA adduct formation is likely to lead to inhibition of PhIP tumorigenicity. We have examined the chemopreventive properties of green tea and black tea in PhIP carcinogenesis by evaluating their effects on PhIP-DNA adduct formation in the female F-344 rat. Young adult animals were maintained on powdered AIN-76A diet while receiving regular drinking water or 2% (wt/vol) infusions of green tea or black tea for a total of six weeks. During Weeks 3, 4, and 5, all animals received PhIP by gavage (1 mg/kg/day). Three rats per group were euthanized on Days 1 and 8 after termination of PhIP exposure. DNA was isolated from a number of organs and analyzed for PhIP-DNA adducts by 32P-postlabeling assays. Compared with animals on regular drinking water, PhIP-DNA adduct formation was inhibited in small intestine, colon, liver, and mammary epithelial cells (MECs) of animals receiving green tea or black tea as the sole source of drinking fluid. Green tea inhibited adduct formation in colon, liver, and MECs (33.3-80.0%) on both days, but only on Day 8 (54.4%) in small intestine. Black tea inhibited adduct formation on both days in liver (71.4-80.0%), on Day 1 in colon (40.0%), and on Day 8 in small intestine (81.8%); it had no effect on MEC adducts. Neither green tea nor black tea had an effect on adduct levels in pancreas, lungs, white blood cells, heart, kidneys, spleen, cecum, or stomach. Similarly, these teas did not affect the rate of adduct removal (percent change from Day 1 to Day 8) in any organ. It is concluded that green tea and black tea are potential chemopreventive agents in PhIP-induced tumorigenesis in the F-344 rat.

Animals↗
PubMed1999

Protective effect of allium vegetables against both esophageal and stomach cancer: a simultaneous case-referent study of a high-epidemic area in Jiangsu Province, China.

To study the relation between allium vegetable intake and cancer of the esophagus (EC) and stomach (SC) in Yangzhong city, which is one of the highest-risk areas for these cancers in Jiangsu province, China, a simultaneous case-referent study was conducted using histopathologically confirmed cases (EC: n = 81, SC: n = 153) and population-based referents (n = 234). A questionnaire was used to collect information on the general status of subjects, their dietary habits, frequency intake of allium vegetables and other foods, tea consumption, smoking and alcohol drinking. The odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by a multiple logistic regression model. The results showed that frequent intake of allium vegetables (including garlic, onion, Welsh onion and Chinese chives), raw vegetables, tomatoes and snap beans, and tea consumption were inversely associated with the risk for EC and SC. In the highest consumption category (> or = 1 time/week) of garlic, onion, Welsh onion and Chinese chives, the adjusted ORs compared with the lowest category (< 1 time/month) were 0.30 (CI = 0.19-0.47), 0.25 (CI = 0.11-0.54), 0.15 (CI = 0.08-0.26), and 0.57 (CI = 0.23-1.42) for EC, and 0.31 (CI = 0.22-0.44), 0.17 (CI = 0.08-0.36), 0.22 (CI = 0.15-0.31) and 0.40 (CI = 0.17-0.94) for SC, respectively. The main results in the present study suggested that allium vegetables, like raw vegetables, may have an important protecting effect against not only stomach cancer, but also esophageal cancer.

Adult↗
PubMed2001

Antimutagenic effect of black tea extract using 'rodent dominant lethal mutation assay'.

The antimutagenic effect of black tea extract has been evaluated with the 'Dominant Lethal Assay' in Swiss albino mice using benzo[a]pyrene [BaP] as a mutagen. BaP was given through the intraperitoneal (i.p.) route at a single dose of 100 mg/kg b.w. to male mice once only. The animals were given 1, 2 and 4% aqueous solution of black tea as sole source of drinking solution prior to BaP. The pregnant females were analyzed for living implants, pre- and post-implantation losses. The results revealed that during mating weeks, BaP caused a reduction in implants and an increase in pre- and post-implantation losses. The protective effect of tea solution on BaP-induced mutagenicity was observed. The number of living implants increased and dead implants decreased significantly in the animals kept on 2 and 4% tea solution. The increase in dominant lethal mutation rate by BaP was inhibited by black tea extract. Four percent tea solution alone did not produce dominant lethality, and reveals that it is non-toxic/non-mutagenic to sperm. Hence the study suggests that tea has a protective effect against BaP-induced genetic damage to germ cells in Swiss albino mice.

Animals↗
PubMed2005

Acute effects of tea on fasting and postprandial vascular function and blood pressure in humans.

BACKGROUND: Effects of regular exposure to polyphenolic compounds found in tea, leading to improved endothelial function and blood pressure, may reduce cardiovascular disease risk. Controlled trials in humans have found that ingestion of tea can improve endothelial function, but also cause a rapid onset acute increase in blood pressure. OBJECTIVE: To examine the acute effects of tea consumption on fasting and postprandial vascular function and blood pressure. METHODS: Endothelium-dependent dilatation of the brachial artery, assessed using ultrasound and blood pressure were measured in 20 participants with a history of coronary artery disease. Measurements were performed at baseline and at 3.5 h (blood pressure) and 4 h (endothelial function) after drinking three cups of black tea or hot water (consumed at time = 0, 1.5 and 3 h) with and without a high-fat (50 g) meal: a total of four treatments administered in random order. RESULTS: The high-fat meal did not impair endothelial function. In comparison to water alone, endothelium-dependent dilatation was increased by the meal with tea (1.7 (0.4, 3.0)%, P = 0.02), but was not significantly altered by the tea alone (0.7 (-0.6, 2.0)%, P = 0.32). Systolic blood pressure was significantly increased by tea alone in comparison to each of the other three groups: water alone (9.3 (4.5, 14.1) mmHg, P = 0.0003), meal with water (9.8 (5.0, 14.6) mmHg, P = 0.0001) and meal with tea (7.2 (2.4,12.0) mmHg, P = 0.004). Consumption of a meal negated the acute increase in systolic blood pressure found with tea in the fasting state. CONCLUSION: Consumption of food may alter the acute effects of tea on vascular function and blood pressure.

Aged↗
PubMed2004

Ex vivo modulation of chemical-induced mutagenesis by subcellular liver fractions of rats treated with rooibos (Aspalathus linearis) tea, honeybush (Cyclopia intermedia) tea, as well as green and black (Camellia sinensis) teas.

Male Fischer rats were given unprocessed (not oxidized) and processed (oxidized) rooibos and honeybush teas as well as green and black teas as a sole source of drinking fluid for 10 weeks, and sub cellular liver fractions were prepared. Cytosolic fractions of rats consuming the unprocessed herbal teas, green and black teas significantly (P < 0.05) protected against 2-acetylaminofluorene (2-AAF)-induced mutagenesis in the Salmonella mutagenicity test with strain TA 98, using Aroclor 1254-induced microsomes. A marginal or no protection was obtained with the processed herbal teas. The mutagenic response of aflatoxin B1 (AFB1) against Salmonella strain TA 100 was significantly (P < 0.05) inhibited by cytosolic fractions from rats treated with processed and unprocessed herbal teas, while no effect was obtained with the green and black teas. Microsomal fractions prepared from livers of rats treated with both the processed and unprocessed rooibos teas and the unprocessed honeybush tea, significantly (P < 0.05) reduced the activation of AFB1 while no protection was observed against 2-AAF-induced mutagenesis. In contrast, microsomal fractions from rats treated with the green, black and unprocessed honeybush teas significantly (P < 0.05) enhanced the mutagenic response of 2-AAF. None of the tea treatments significantly affected the concentration of the microsomal liver cytochrome P450.

Animals↗
PubMed2003

Stimulatory effect of oral administration of green tea and caffeine on locomotor activity in SKH-1 mice.

Administration of green tea or caffeine was shown previously to inhibit ultraviolet B light-induced carcinogenesis in SKH-1 mice, and this effect was associated with a reduction in dermal fat. In the present study, oral administration of 0.6% green tea (6 mg tea solids/ml) or 0.04% caffeine (0.4 mg/ml; equivalent to the amount of caffeine in 0.6% green tea) as the sole source of drinking fluid to SKH-1 mice for 15 weeks increased total 24 hr locomotor activity by 47 and 24%, respectively (p<0.0001). Oral administration of 0.6% decaffeinated green tea (6 mg tea solids/ml) for 15 weeks increased locomotor activity by 9% (p<0.05). The small increase in locomotor activity observed in mice treated with decaffeinated green tea may have resulted from the small amounts of caffeine still remaining in decaffeinated green tea solutions (0.047 mg/ml). The stimulatory effects of orally administered green tea and caffeine on locomotor activity were paralleled by a 38 and 23% increase, respectively, in the dermal muscle layer thickness. In addition, treatment of the mice with 0.6% green tea or 0.04% caffeine for 15 weeks decreased the weight of the parametrial fat pad by 29 and 43%, respectively, and the thickness of the dermal fat layer was decreased by 51 and 47%, respectively. These results indicate that oral administration of green tea or caffeine to SKH-1 mice increases locomotor activity and muscle mass and decreases fat stores. The stimulatory effect of green tea and caffeine administration on locomotor activity described here may contribute to the effects of green tea and caffeine to decrease fat stores and to inhibit carcinogenesis induced by UVB in SKH-1 mice.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1996

Black tea, green tea, and tea polyphenols. Effects on trace element status in weanling rats.

Previous studies have shown that tea consumption can impair trace element metabolism, particularly iron status, and increase the risk of anemia in humans and animals. More recently, however, evidence has been accumulating to show that, in animals, consumption of green tea or its polyphenols is associated with a reduction of the incidence and severity of a variety of experimentally induced cancers. In this study we have monitored the growth, trace element status, including hematological parameters of weanling rats given either (1) water, (2) 1% black tea, (3) 1% green tea, or (4) 0.2% crude green tea extract as their sole drinking fluid while consuming diets containing either adequate or low amounts of iron. With the exception of manganese, none of the trace elements studied (iron, copper, zinc, and manganese) or the hematological indices measured were affected by the type of beverage supplied, even though the polyphenol extract was shown to chelate metals in vitro and all the animals fed the low iron diet were shown to be anemic. There appeared to be an effect of black and green teas on manganese balance in both the first and last weeks of the study. A lower level of brain manganese was associated with green tea consumption, and a higher level of this element in the kidneys of animals fed black tea. The results demonstrate that both black and green teas and a green tea polyphenol extract do not represent a risk to animals consuming the beverages as their sole fluid intake with respect to iron availability, although the interactions with manganese deserve further study.

Animals↗
PubMed2004

Green tea catechins inhibit neointimal hyperplasia in a rat carotid arterial injury model by TIMP-2 overexpression.

OBJECTIVE: Although it has been demonstrated that the antioxidant properties of tea catechins reduce atherosclerotic lesions in various animal models of hyperlipidemia, it is not yet clear whether these catechins prevent hyperlipidemia-independent arterial remodeling induced by balloon angioplasty. We evaluated the influence of the administration of the tea extract on vascular remodeling in a rat carotid artery balloon-injury model. METHODS AND RESULTS: Male Wistar rats were supplied drinking water with or without green tea extract (1 mg/ml) supplement. Administration of the tea extract reduced the area of the intima (30%) and the ratio of the intimal area to the medial area (36.2%) in injured arteries compared with those of control rats at 14 days after the injury. Real-time RT-PCR, Western blot, and gelatin zymography revealed a significant increase in tissue inhibitor of matrix metalloproteinase (MMP)-2 (TIMP-2) expression as well as a significant reduction of gelatinolytic net activity and activated MMP-2 levels in the injured arteries as a result of the administration of the tea extract compared with those of control group. Similarly, epigallocatechin-3-gallate, a major constituent of green tea catechins, significantly upregulated TIMP-2 expression in cultured smooth muscle cells. Immunohistochemical analysis showed that the increase of TIMP-2 protein occurred preferentially in the developing neointima. CONCLUSION: These results indicate that catechins inhibit intimal hyperplasia in a rat balloon-injury model through the upregulation of TIMP-2 expression to modulate MMP activity.

Angioplasty, Balloon↗