Estrogen replacement in postmenopausal women activates the renin-angiotensin system at rest and during simulated orthostatic stress but lowers blood pressure
Bibliographic record
Abstract
Menopause is associated with activation of the tissue renin-angiotensin system (RAS) through upregulation of both angiotensin converting enzyme (ACE) activity and angiotensin II (Ang II) type 1 receptor expression. Estrogen replacement therapy (ERT) is known to increase circulating angiotensinogen and Ang II in resting conditions but end-organ responsiveness to this humoral activation is not well characterized. The aim of this study in postmenopausal women (PMP) was to determine the blood pressure (BP) and RAS responses to 1 month of ERT both at rest and during stimulation of the RAS by graded lower body negative pressure (LBNP). In 13 normotensive (BP≤140/90) PMP women (54±2yrs)(mean±SE) supine BP, heart rate (HR), renin, angiotensinogen, plasma renin activity (PRA), Ang II and aldosterone were measured at rest, during incremental LBNP (-10, -20 and -40 mmHg) and 15 mins afterwards. All measurements were repeated after 4 weeks of estradiol 2 mg daily. Baseline values for PRA (P<0.05), Ang II (P<0.01) and angiotensinogen (P<0.001) were significantly higher but aldosterone and renin were unchanged post-ERT. The increase in these components of the RAS induced by LBNP was significantly greater post-ERT and was further augmented during recovery from LBNP. Despite this increase in Ang II, mean arterial BP was significantly lower at both rest (P<0.05) and during LBNP (P<0.01) when compared to pre-ERT. ERT did not influence rest HR or reflex HR during LBNP. Pre-syncope during -40 mmHg LBNP was twice as common post-ERT (4vs2). Despite an increase in circulating RAS following oral ERT there is no increase in aldosterone, a reduction in resting BP and diminished capacity to defend BP during simulated orthostatic stress. These results suggest that ERT may protect against activation of the RAS by down-regulating tissue responsiveness to Ang II either directly at the receptor level or alternatively by modifying counterregulatory hypotensive mechanisms. In pathological states such as hypertension and congestive cardiac failure, this attenuation by ERT may protect this high risk population against the potentially deleterious effects of Ang II.
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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".