ESTROGEN REPLACEMENT, VASCULAR DISTENSIBILITY, AND BLOOD PRESSURES INPOSTMENOPAUSAL WOMEN

The pathogenesis of blood pressure (BP) rise in aging women remains un explained, and one of the many incriminating factors may include abnor malities in arteriolar resistance vessels. The aim of this study was t o determine the effects of unopposed estrogen on arteriolar distensibi lity, baroreceptor sensitivity (BRS), BP changes, and rate-pressure pr oduct (RPP). We tested the hypotheses that estrogen replacement therap y (ERT) enhances arteriolar distensibility and ameliorates BRS, which leads to decreases in BP and RPP. Postmenopausal women participated in a single-blind crossover study; the participants of this study, after baseline measurements, were randomly assigned to receive estrogen (ER T) or a drug-free treatment with a 6-wk washout period between treatme nts. The single-blind design was instituted because subjects become un blinded due to physiological changes (i.e., fluid shifts, weight gain, and secretory changes) associated with estrogen intake. However, inve stigators and technicians involved in data collection and analyses rem ained blind. After each treatment, subjects performed identical autono mic tests, during which electrocardiograms, beat-by-beat BPs, and resp iration were recorded. The area under the dicrotic notch of the BP wav e was used as an index of arteriolar distensibility The magnitude of t he reflex bradycardia after a precipitous rise in BP was used to deter mine BRS. Power spectral analysis of heart rate variability was used t o assess autonomic activity. BPs were recorded from resistance vessels in the finger using a beat-by-beat photoplethysmographic device. RPP, a noninvasive marker of myocardial oxygen consumption, was calculated . Repeated-measures analyses of variance revealed a significantly enha nced arteriolar distensibility and BRS after ERT (P < 0.05). A trend o f a lower sympathovagal balance at rest was observed after ERT; howeve r, this trend did not reach statistical significance (P = 0.061) compa red with the other treatments. The above autonomic changes produced si gnificantly lower systolic and diastolic BP changes and RPPs (P < 0.05 ) at rest and during isometric exercise. We conclude that short-term u nopposed ERT favorably enhances arteriolar distensibility, BRS, and he modynamic parameters in postmenopausal women. These findings have clin ical implications in the goals for treating cardiovascular risk factor s in aging women.