ATP increases [Ca<sup>2+</sup>]<sub>i</sub>and activates a Ca<sup>2+</sup>‐dependent Cl<sup>−</sup>current in rat ventricular fibroblasts
Bibliographic record
Abstract
New Findings What is the central question of this study? Although electrophysiological and biophysical characteristics of heart fibroblasts have been studied in detail, their responses to prominent paracrine agents in the myocardium have not been addressed adequately. Our experiments characterize changes in cellular electrophysiology and intracellular calcium in response to ATP. What is the main finding and its importance? In rat ventricular fibroblasts maintained in cell culture, we find that ATP activates a specific subset of Ca2+‐activated Cl−channels as a consequence of binding to P2Y purinoceptors and then activating phospholipase C. This response is not dependent on [Ca2+]obut requires an increase in [Ca2+]iand is modulated by the type of nucleotide that is the purinergic agonist. Abstract Effects of ATP on enzymatically isolated rat ventricular fibroblasts maintained in short‐term (36–72 h) cell culture were examined. Immunocytochemical staining of these cells revealed that a fibroblast, as opposed to a myofibroblast, phenotype was predominant. ATP, ADP or uridine 5′‐triphosphate (UTP) all produced large increases in [Ca2+]i. Voltage‐clamp studies (amphotericin‐perforated patch) showed that ATP (1–100 μm) activated an outwardly rectifying current, with a reversal potential very close to the Nernst potential for Cl−. In contrast, ADP was much less effective, and UTP produced no detectable current. The non‐selective Cl−channel blockers niflumic acid, DIDS and NPPB (each at 100 μm), blocked the responses to 100 μmATP. An agonist for P2Y purinoceptors, 2‐MTATP, activated a very similar outwardly rectifying C1−current. The P2Y receptor antagonists, suramin and PPADS (100 μmeach), significantly inhibited the Cl−current produced by 100 μmATP. ATP was able to activate this Cl−current when [Ca2+]owas removed, but not when [Ca2+]iwas buffered with BAPTA‐AM. In the presence of the phospholipase C inhibitor U73122, this Cl−current could not be activated. PCR analysis revealed strong signals for a number of P2Y purinoceptors and for the Ca2+‐activated Cl−channel, TMEM16F (also denoted ANO6). In summary, these results demonstrate that activation of P2Y receptors by ATP causes a phospholipase C‐dependent increase in [Ca2+]i, followed by activation of a Ca2+‐dependent Cl−current in rat ventricular fibroblasts.
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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 | 0.000 |
| 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) | 0.001 | 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 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".