The putative role of HCN channels in acid-base compensatory mechanisms of lobster
Bibliographic record
Abstract
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are highly conserved proteins that have gained recent attention as ammonium transporters involved in acid-base regulation of mammalian kidneys. The specific inhibition of these channels by ZD7288 in perfused gills of the European green shore crab, Carcinus maenas, supports a similar acid-secretory function in crustaceans by enhancing ammonium excretion rates and alleviating hypercapnic stress. The present work investigated whether HCN channels present within the trichobranchiate gills and epipodites of the American lobster, Homarus americanus, hold a similar functional role. Investigation of mRNA transcript abundances of an identified HCN channel across the pluero-, arthro-, and podobranch gills as well as epipodites of the lobster revealed no statistical differences. The capacity of isolated and perfused lobster gills to alkalize an artificial hemolymph-like saline was significantly reduced when HCN channel activity was inhibited by adding ZD7288 to the basolateral perfusion saline. This impairment coincided with a significant 0.3-fold impairment of transbranchial ammonium excretion rates as well as significant 0.28-fold reductions in the transbranchial transport of inorganic carbon as assessed by CO2 excretion rates and HCO3 - accumulation rates. Hemi-epipodites mounted in an Ussing chamber yielded similar results, except that ZD7288 evokes a 17.8-fold increase in transepithelial HCO3 - excretion rates. Functional expression of the lobster HCN channel reduced the rate that the ammonium ion proxy methylamine accumulated within Xenopus laevis oocytes. Methylamine uptake was confirmed to be blocked upon exposing the oocytes to ZD7288 as well as low pH environments, suggesting that the HCN channel function is acid sensitive.
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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".