Expression of purinergic P2X<sub>2</sub> receptor-channels and their role in calcium signaling in pituitary cells
Bibliographic record
Abstract
Pituitary cells express purinergic receptor-channels (P2XR), the activation of which by ATP is associated with the facilitation of Ca2+ influx. Pharmacological, RT-PCR, and nucleotide sequence analyses confirm the presence of a wild type P2X2aR and a spliced isoform P2X2bR, which lacks a portion of carboxyl terminal amino acids. Wild type and spliced isoform receptors have a similar EC50 for ATP and time-course for activation, but the spliced isoform exhibits rapid and complete desensitization, whereas the wild type channel desensitizes slowly and incompletely. Deletion and insertion studies have revealed that a 6 residue sequence located in carboxyl tail (Arg371-Pro376) is required for sustained Ca2+ influx through wild type receptors. When co-expressed, the wild type and spliced channels form functional heteropolymeric channels. The patterns of Ca2+ signaling in the majority of pituitary cells expressing ATP-gated receptor-channels are highly comparable to those observed in cells co-transfected with P2X2aR and P2X2bR. ATP-induced [Ca2+]i response in pituitary cells is partially inhibited by nifedipine, a blocker of voltage-gated L-type Ca2+ channels, suggesting that P2X2R not only drive Ca2+ into the cell, but also activate voltage-gated Ca2+ entry. Our results indicate that ATP represents a paracrine and (or) autocrine factor in the regulation of Ca2+ signaling, and that its actions are mediated in part by heteropolymeric P2X2R.
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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".