H <sup>+</sup> Induces Arteriolar Vasodilation but Does Not Initiate a Conducted Response in Skeletal Muscle Microvasculature
Bibliographic record
Abstract
Active hyperemia is the process where blood flow is recruited to a tissue to meet increased metabolic demand. Conducted responses are important to this process in order to direct blood flow to capillaries to feed active skeletal muscle fibres. A conducted response is a coordinated vasodilatory signal that travels from low to high branch order arterioles resulting in an increase in capillary perfusion. Conducted responses are hypothesized to be initiated by metabolic vasodilators ‐ byproducts of skeletal muscle metabolism‐ however, exactly which metabolites are involved remains unclear. Two vasodilatory metabolites of skeletal muscle metabolism are hydrogen ion (H + ) and carbon dioxide (CO 2 ). Both H + and CO 2 are interrelated through the bicarbonate (HCO 3 − ) buffer (HCO 3 − + H + <‐‐> H 2 CO 3 <‐‐> CO 2 + H 2 O) whereby H + reacts with HCO 3 − to produce CO 2 and CO 2 reacts in reverse to produce H + . Thus, it is difficult to study the individual effects of these metabolites. In order to separate them we used a Tris (amine) buffer to superfuse the preparation, to allow us to apply H + without changing CO 2 , thus allowing us to investigate the vasodilatory actions of H + independently. Using an in situ, intact hamster cremaster muscle model, H + was applied to the whole preparation through the superfusate or to a small region of a 2A arteriole (max. diameter approx. 40μm) via micropipette. Arteriolar diameter was recorded and analyzed offline. A range of H + concentrations (63.1 – 251.2 nMol; pH 7.2 – 6.6) applied to the entire preparation induced arteriolar vasodilation. The maximum change in diameter was 9.9±2.1μm, which was not a maximal dilation in the arteriole (only 71.1% of maximal diameter). Micropipette application of 251.2 nMol H + (pH 6.6), induced a local arteriolar vasodilation of 3.5±0.4μm however it did not elicit a significant vasodilation 1000μm upstream of the micropipette application site. These novel data demonstrate that H + is a local arteriolar vasodilator with a limited capacity to cause vasodilation and does not cause a conducted response, which is important in directing blood flow to active skeletal muscle cells during active hyperaemia. These data bring into question the importance of H + and changes in pH in the active hyperaemic response. Support or Funding Information NSERC, Canada
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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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.006 | 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".