Sex differences in mechanisms of cardiac excitation-contraction coupling in rat ventricular myocytes
Bibliographic record
Abstract
Components of excitation-contraction (E-C) coupling were compared in ventricular myocytes isolated from 3-mo-old male and female rats. Ca(2+) concentrations (fura-2) and cell shortening (edge detector) were measured simultaneously (37 degrees C). Membrane potential and ionic currents were measured with microelectrodes. Action potentials were similar in male and female myocytes, but contractions were smaller and slower in females. In voltage-clamped cells, peak contractions were smaller in females than in males (5.1 +/- 0.7% vs. 7.7 +/- 0.8% diastolic length, P < 0.05). Similarly, Ca(2+) transients were smaller in females than in males and the rate of rise of the Ca(2+) transient was slower in females. Despite smaller contractions and Ca(2+) transients in females, Ca(2+) current density was similar in both groups. Sarcoplasmic reticulum Ca(2+) content, assessed with caffeine, did not differ between the sexes. However, E-C coupling gain (rate of Ca(2+) release/Ca(2+) current) was smaller in females than in males (157.0 +/- 15.6 vs. 338.4 +/- 54.3 (nM/s)/(pA/pF), P < 0.05). To determine whether the reduced gain in female cells was due to changes in unitary Ca(2+) release, spontaneous Ca(2+) sparks were evaluated (fluo-4, 37 degrees C). Spark frequencies and widths were similar in both groups, but spark amplitudes were smaller in females than in males (0.56 +/- 0.01 vs. 0.64 +/- 0.01 DeltaF/F(0), P < 0.05). Spark durations also were shorter in females than in males (full duration at half-maximum = 14.86 +/- 0.17 vs. 16.25 +/- 0.27 ms, P < 0.05). These observations suggest that decreases in the size and duration of Ca(2+) sparks contributes to the decrease in E-C coupling gain in female myocytes. Thus, differences in cardiac contractile function arise, in part, from differences in unitary Ca(2+) release between the sexes.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".