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Wednesday, Apr 14th

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Lung Tumorigenesis

Black tea Constituents, Theaflavins, Inhibit 4–(methylnitrosamino) –1– (3– pyridyl)–1–butanone (NNK)–induced lung Tumorigenesis in A/J mice

The present study investigated the inhibitory activity against lung tumorigenesis by a group of characteristic black tea polyphenols, theaflavins. In a short–term study, female A/J mice were treated with a single dose of 4–(methylnitrosamino) –1–(3–pyridyl)–1–butanone (NNK; 103 mg/kg b.w., i.p.) on day 0, and 0.1 and 0.3% theaflavins were administered as the sole source of drinking fluid starting 24 h after NNK treatment. The proliferation index of the lung tissues was measured by the incorporation of bromodeoxyuridine (BrdU) immunohistochemically. The highest NNK–induced proliferation rate of bronchiolar cells, observed on day 5, was significantly decreased by 0.3% theaflavins (proliferation index, 1.51 +/– 0.08 versus 2.35 +/– 0.16). In a long– term lung tumorigenesis study, pulmonary adenomas were observed in 100% (30/30) of the mice at week 16 after NNK treatment. Administration of theaflavins (0.1%) as the sole source of drinking fluid, starting 2 days after the NNK treatment until the termination of the experiment, significantly reduced the tumor multiplicity and volume by 23% (8.5 +/– 0.6 versus 6.5 +/– 0.6 tumors/mouse) and 34% (0.08 versus 0.05 mm3 per tumor), respectively. The proliferation index in lung adenomas was also significantly inhibited by theaflavins. The present work demonstrates the inhibitory action of theaflavins against NNK–induced pulmonary


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