Heteroactivation of cytochrome P450 1A1 by teas and tea polyphenols
Bibliographic record
Abstract
We studied 7-ethoxyresorufin deethylase as an index of cytochrome P4501A1 (CYP1A1) activity in liver microsomes from rats pretreated with 3-methylcholanthrene. The enzyme had complex kinetics compatible with a multisite model. At 1 microM substrate, brewed black, green and white teas had complex effects on enzyme activity consisting of activation at low concentrations and inhibition at higher concentrations. Data fit well to a two-site model that allowed us to determine maximal activation (% increase above control), pEC(50) for activation (g ml(-1)) and pIC(50) for inhibition (g ml(-1)). These parameters were 190+/-40, 5.9+/-0.1 and 4.51+/-0.09 for green tea, 350+/-40, 5.43+/-0.05 and 5.43+/-0.05 for black tea and 230+/-80, 5.3+/-0.3 and 4.7+/-0.2 for white tea, respectively. The effects of the brewed teas were mimicked to different degrees by the green tea polyphenols. Maximal activation, pEC(50) (M) and pIC(50) (M) were: (-)-epicatechin, 55+/-9, 5.4+/-0.3, 2+/-1; (-)-epicatechin gallate, 160+/-60, 6.2+/-0.3, 5.28+/-0.06; (-)-epigallocatechin 30+/-10, 6.5+/-0.5, 3.37+/-0.08; and (-)-epigallocatechin gallate 130+/-40, 6.7+/-0.3, 5.0+/-0.1. A crude extract of black tea polyphenols inhibited 7-ethoxyresorufin deethylase, but did not cause enzyme activation consistently. Enzyme activation was dependent upon substrate concentration. Heteroactivation of CYP1A1 may partially explain the lack of agreement between biological and epidemiological evidence of a role for tea in cancer prevention.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".