Estrogen replacement therapy improves baroreflex regulation of vascular sympathetic outflow in postmenopausal women.
BACKGROUND
Menopausal estrogen loss has been associated with increased cardiovascular disease in postmenopausal women. However, the link between estrogen and cardiovascular disease remains unclear. Some data suggest estrogen mediates its effect through changes in arterial pressure and its regulation. However, the data available in older women are equivocal regarding estrogen's ability to reduce resting arterial pressure or to improve its regulation.


RESULTS
We studied 11 healthy, postmenopausal women before and after 6 months of estrogen administration. Arterial pressure was measured by brachial auscultation and finger photoplethysmography. Vascular sympathetic nerve activity was measured in the peroneal nerve by microneurography, and the slope of the relations between changes in heart period, sympathetic activity, and arterial pressure caused by bolus infusions of nitroprusside and phenylephrine were used as an index of baroreflex gain. Estrogen therapy did not change systolic pressure (128+/-2 versus 123+/-2 mm Hg) or cardiac-vagal baroreflex gain (6.6+/-0.9 versus 6.7+/-0.7 ms/mm Hg). However, vascular sympathetic baroreflex gain was increased (-4.6+/-0.6 versus -7.4+/-1.0 arbitrary integrated units/mm Hg; P=0.02).


CONCLUSIONS
These findings suggest long-term estrogen replacement therapy has effects on cardiovascular regulation that may not be reflected in resting arterial pressures.
Hunt
B E
BE
Laboratory for Cardiovascular Research, Research and Training Institute, Hebrew Rehabilitation Center for Aged, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA. hunt@mail.hrca.harvard.edu
Taylor
J A
JA
Hamner
J W
JW
Gagnon
M
M
Lipsitz
L A
LA
D000284:Administration, Oral; D017704:Baroreflex / Q000187:drug effects* / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects; D004334:Drug Administration Schedule; D015914:Estrogen Replacement Therapy; D004967:Estrogens / Q000008:administration & dosage; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007262:Infusions, Intravenous; D008875:Middle Aged; D009599:Nitroprusside / Q000008:administration & dosage; D010543:Peroneal Nerve / Q000187:drug effects / Q000502:physiology; D017698:Postmenopause; D011374:Progesterone / Q000008:administration & dosage; D016683:Supine Position / Q000502:physiology; D014630:Vagus Nerve / Q000187:drug effects / Q000502:physiology; D014666:Vasomotor System / Q000187:drug effects* / Q000502:physiology
D004967:Estrogens; D009599:Nitroprusside; D011374:Progesterone