Section-specific H+ fluxes in renal tubules of fasted and fed goldfish
Bibliographic record
Abstract
A recent study demonstrated that in response to a feeding-induced metabolic acidosis, goldfish Carassius auratus adjust epithelial protein and/or mRNA expression in their kidney tubules for multiple transporters known to be relevant for acid-base regulation. These include Na+/H+-exchanger, V-H+-ATPase, cytoplasmic carbonic anhydrase, HCO3−-transporters, and Rhesus proteins. Consequently, renal acid output in the form of protons and NH4+ increases. Little, however, is known about mechanistic details of renal acid-base regulation in C. auratus and teleost fishes in general. The present study applied the Scanning Ion-selective Electrode Technique (SIET) to measure proton flux in proximal, distal and connecting tubules of goldfish. We detected increased H+ efflux into the extracellular fluid from the tubule in fed animals, resulting from paracellular back-flux of H+ through the tight junction. By applying inhibitors for selected acid-base regulatory epithelial transporters, we found that cytosolic carbonic anhydrase and HCO3− transporters were important in mediating H+ flux in all three tubule segments of fed goldfish. Contrastingly, V-H+-ATPase seemed to play a role for H+ flux only in proximal and distal tubule, and Na+/H+-exchanger in proximal and connecting tubule. We develop working models for transport of acid-base relevant equivalents (H+, HCO3−, NH3/NH4+) for each tubule segment in C. auratus kidney. While the proximal tubule appears to play a major role in both H+ secretion and HCO3− reabsorption, the distal and connecting tubules seem to mainly serve for HCO3− reabsorption and NH3/NH4+ secretion.
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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".