Bicarbonate‐dependent chloride transport drives fluid secretion by the human airway epithelial cell line Calu‐3
Bibliographic record
Abstract
Anion transport by the airway is defective in cystic fibrosis (CF), but its mechanisms and roles in fluid secretion are not well understood. We studied Cl − and HCO 3 − fluxes across Calu‐3 cells, calculated the equivalent short‐circuit current (I eq ) under open circuit conditions, and measured fluid secretion by monolayers. Forskolin stimulated I eq , J HCO3− and fluid secretion. Bumetanide reduced secretion by ~20%, but had no effect on HCO 3 − transport. Although secretion was abolished in Na + ‐free or HCO 3 − ‐free solution, significant J HCO3− was maintained in Cl − ‐free solution. DIDS was inhibitory in normal and Cl − ‐free solutions. Using apical permeabilization we demonstrated an exchange of intracellular HCO 3 − for basolateral Cl − or NO 3 − , but not for gluconate. Adding basolateral NO 3 − to low‐Cl − medium restored fluid secretion. Acetazolamide greatly inhibited anion transport. Our data show that basolateral anion exchange plays an important role in Cl − loading and fluid secretion. NBC mediates HCO 3 − entry and carbonic anhydrase contributes significantly to the intracellular accumulation of HCO 3 − . Although HCO 3 − is essential for fluid secretion, most HCO 3 − is recycled to the basolateral side in exchange for Cl − , thus fluid transport depends mainly on J Cl− rather than J HCO3− . HCO 3 − secretion persists in Cl − ‐free solution and is sensitive to CFTR blockers, suggesting apical HCO 3 − exit is mediated by CFTR.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 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".