Sequential transformation of 4-androstenedione into dihydrotestosterone in prostate carcinoma (DU-145) cells indicates that 4-androstenedione and not testosterone is the substrate of 5α-reductase
Bibliographic record
Abstract
BACKGROUND: Although it is well recognized that 5α-reductases possess higher affinity for 4-androstenedione than testosterone, and the affinity of 4-androstenedione is higher for 5α-reductases than 17β-hydroxysteroid dehydrogenases, it is generally believed that dihydrotestosterone is necessarily produced by the transformation of testosterone into dihydrotestosterone, suggesting that the step catalyzed by 17β-hydroxysteroid dehydrogenase precedes the step catalyzed by 5α-reductase. This interpretation is in contradiction with the enzymatic kinetic law that suggests that the 5α-reduction step that catalyzes the transformation of 4-dione into 5α-androstane-3,17-dione precedes the 17keto-reduction step. MATERIALS AND METHODS: To verify which of these two pathways is operative, we quantified mRNA expression levels of steroidogenic enzymes in prostate carcinoma DU-145 cells by real-time PCR and determined the metabolites produced after incubation with [14C]4-dione in the presence and absence of a 5α-reductase inhibitor and analyzed the metabolites produced by thin layer chromatography and HPLC. RESULTS: Real-time PCR analysis strongly suggests that the new type 3 5α-reductase is responsible for 5α-reductase activity in DU-145 cells. Steroid profile analysis shows that in the absence of inhibitor 5α-androstanedione is first produced, followed by the production of androsterone and dihydrotestosterone. The concentration of testosterone was not detectable. In the presence of Finasteride, an inhibitor of 5α-reductase, there was no transformation of 4-androstenedione and also there was no production of testosterone. The present data clearly indicate that the biosynthesis of dihydrotestosterone in DU-145 cells does not require testosterone as intermediate, and the step catalyzed by 5α-reductase precedes the step catalyzed by 17β-hydroxysteroid dehydrogenase.
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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) | 0.001 | 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".