The phosphoinositide 3-kinase inhibitor LY294002 enhances cardiac myocyte contractility via a direct inhibition of Ik,slow currents
Bibliographic record
Abstract
OBJECTIVE: Phosphoinositide 3-kinase (PI3K) is a key component in regulating myocardial growth, survival and contractility. LY294002 and wortmannin are two PI3K inhibitors used widely to establish the role of PI3K. The goal of this study was to examine the effects of acute application of LY294002 and wortmannin on cardiac myocyte contractility and underlying mechanisms. METHODS: Patch-clamp, indo-1 epifluorescence and video-edge detection techniques were used to measure outward K(+) currents, action potentials (AP), Ca(2+) transients and shortening of myocytes isolated from mouse left ventricular free wall. RESULTS: In field-stimulated myocytes, LY294002 (10 micromol/l) increased Ca(2+) transient amplitude by 23%, and cell shortening amplitude by 60% in the absence or presence of wortmannin, while wortmannin alone had no effect. LY294002 (but not wortmannin) prolonged AP duration by specifically inhibiting slowly inactivating K(+) currents (i.e., the 4-aminopyrydine-sensitive I(k,slow1) and the tetraethylammonium-sensitive I(k,slow2)), leading to an increase in sarcoplasmic reticular Ca(2+) levels. It appeared that the AP prolongation was responsible for elevated contractility since AP-clamp of myocytes with prolonged APs (recorded in LY294002-treated myocytes) induced a 29% increase in cell shortening compared with control APs, while LY294002 application did not increase contractility in voltage-clamp studies using either step or AP depolarizations. CONCLUSIONS: The putative PI3K inhibitor LY294002 increases Ca(2+) release and myocyte contractility via direct inhibition of cardiac I(k,slow) and AP prolongation, thus limiting the usefulness of this agent in the analyses of the role of PI3K in heart function.
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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 | 0.004 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.002 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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".