Extracellular Ba<sup>2+</sup>blocks the cardiac transient outward K<sup>+</sup>current
Bibliographic record
Abstract
Ba(2+) is widely used as a tool in patch-clamp studies because of its ability to block a variety of K(+) channels and to pass Ca(2+) channels. Its potential ability to block the cardiac transient outward K(+) current (I(to)) has not been clearly documented. We performed whole cell patch-clamp studies in canine ventricular and atrial myocytes. Extracellular application of Ba(2+) produced potent inhibition of I(to) with an IC(50) of approximately 40 microM. The effects were voltage independent, and the inactivation kinetics were not altered by Ba(2+). The potency of Ba(2+) was approximately 10 times higher than that of 4-aminopyridine (a selective I(to) blocker with an IC(50) of 430 microM) under identical conditions. By comparison, Ba(2+) blockade of the inward rectifier K(+) current was voltage dependent; the IC(50) was approximately 20 times lower (2.5 microM) than that for I(to) when determined at -100 mV and was comparable to I(to) as determined at -60 mV (IC(50) = 26 microM). Ba(2+) concentrations of </=1 mM or higher failed to block ultrarapid delayed rectifier K(+) current. Our data suggest that Ba(2+) can be considered a potent blocker of I(to).
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".