Sex Differences in Blood Pressure Regulation During Ischemic Isometric Exercise: The Role of the β‐Adrenergic Receptors
Bibliographic record
Abstract
Sex differences have been reported in the respective contribution of cardiac output (Q̇) and vascular constriction to the pressor response to isometric handgrip exercise (IHE). Differently from men, the majority of the blood pressure (BP) response to IHE in young women is due to elevated Q̇ rather than elevations in total peripheral resistance (TPR). The underlying mechanisms for these differences are unknown, but previous data suggest that the β‐adrenergic receptors offset α‐adrenergic vasoconstriction in young women under resting condition. Whether this could be extended to an exercise condition remains to be determined. Given this, the aim of the present study was to investigate whether the β‐adrenergic receptors play a pivotal role in sex‐related differences in the BP regulation during ischemic IHE. Ten men (21 ± 0.6 years) and 9 women (23 ± 1.3 years) healthy and physically active volunteers were recruited. All women were non‐oral contraceptives users and performed experiments in the early follicular phase of the menstrual cycle. To make the forearm ischemic prior to exercise, a 3 min period of circulatory arrest was achieved by inflating an upper arm cuff to supra systolic pressure. This cuff remained inflated for 2 min of isometric exercise at 30% of maximal voluntary contraction force, and 2 min of post‐exercise circulatory occlusion (PECO). Beat‐to‐beat heart rate (HR) (electrocardiography) and arterial BP (finger photopletysmography) were continuously measured. Beat‐to‐beat changes in stroke volume (SV) was obtained with Modelflow method and matched with the responses of heart rate (HR) to estimate Q̇ (Q̇=SV x HR) and TPR (TPR=Mean BP/Q). The exercise and PECO responses were analyzed using the peak change. Two trials were randomly conducted in different days either placebo or non‐selective β‐adrenergic blockade (40mg propranolol). During ischemic IHE under placebo condition, mean BP increased from rest in both men and women, however the magnitude of these responses was greater in men. During PECO, the mean BP remained elevated and the sex differences persisted. The β‐adrenergic blockade attenuated the mean BP response during ischemic IHE from rest in men (Δ 51 ± 6 mmHg vs Δ 39 ± 6 mmHg, P<0.01) but not in women (Δ 28 ± 5 mmHg vs Δ 32 ± 5mmHg, P=0.17). This attenuated mean BP response observed in men under β‐blockade could be explained by a reduction in Q̇ (Δ 3.0 ± 0.4l/min vs Δ 1.2 ± 0.2 l/min, P<0.01). This was less pronounced in women (Δ 2.0 ± 0.4 l/min vs Δ 1.0 ± 0.2 l/min, P=0.05). In addition, vascular constriction was increased during ischemic IHE and PECO in men and these responses were not affected by β‐blockade. In contrast, increases in TPR were greater in women under β‐adrenergic blockade during both ischemic IHE (Δ 1.2 ± 0.7 mmHg.L‐1.min vs Δ 3.3 ± 0.9 mmHg.L‐1.min, P=0.03) and PECO (Δ 4.5 ± 0.9 mmHg.L‐1.min vs Δ 6.8 ± 1.1 mmHg.L‐1.min, P=0.04). These findings demonstrate for the first time that the sex differences in arterial BP regulation during ischemic IHE are mediated by β‐adrenergic receptors. Support or Funding Information Funding: CNPq, FAPDF, CAPES and an American Physiological Society Arthur C. Guyton Awards for Excellence in Integrative Physiology (to L.C. Vianna). This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .
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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) | 0.002 | 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".