Role of glucocorticoid receptor and pregnane X receptor in dexamethasone induction of rat hepatic aryl hydrocarbon receptor nuclear translocator and NADPH‐cytochrome P450 oxidoreductase (LB597)
Bibliographic record
Abstract
The aryl hydrocarbon receptor (AHR) nuclear translocator (ARNT), as the AHR’s heterodimerization partner, and NADPH‐cytochrome P450 oxidoreductase (POR), as the key electron donor for all microsomal P450s, are important players in the adaptive and toxic responses to polycyclic and halogenated aromatic hydrocarbons. Expression of both ARNT and POR in rat liver is induced by dexamethasone (DEX), a synthetic glucocorticoid known to activate both the glucocorticoid receptor (GR) and the pregnane X receptor (PXR). To study the role of GR in ARNT and POR regulation, we treated male rats with a low DEX dose (0.5 mg/kg), shown to activate GR selectively, and a high DEX dose (50 mg/kg), shown to activate both GR and PXR, in the absence and presence of the GR antagonist RU486 (50 mg/kg). The role of PXR was assessed by comparing the responses to similar low (1 mg/kg) and high (50 mg/kg) DEX doses in wild‐type and PXR‐ knockout rats. In both studies, rats were euthanized at 6 and 24 h after DEX dosing. The induction of ARNT mRNA levels by low‐dose DEX and the increase in ARNT protein levels by high‐dose DEX were prevented by RU486, whereas the induced levels of ARNT mRNA and protein did not differ between wild‐type and PXR‐ knockout rats. RU486 did not inhibit the induction by DEX of POR expression at the mRNA, protein, and catalytic activity levels. The induction of POR mRNA levels by low‐ and high‐dose DEX was significantly attenuated in PXR‐ knockout rats and the increase in POR protein levels and catalytic activity by high‐dose DEX was completely absent in PXR‐ knockout rats. These results are consistent with important roles for GR in the DEX induction of rat hepatic ARNT and PXR in the DEX induction of rat hepatic POR . Grant Funding Source : Supported by the Canadian Institutes of Health Research
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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 source (direct Gemma or distilled Codex), 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".