Short-term administration of progesterone and estradiol independently alter carotid-vasomotor, but not carotid-cardiac, baroreflex function in young women

Abstract

Brunt VE, Miner JA, Kaplan PF, Halliwill JR, Strycker LA, Minson CT. Short-term administration of progesterone and estradiol independently alter carotid-vasomotor, but not carotid-cardiac, baroreflex function in young women. Am J Physiol Heart Circ Physiol 305: H1041-H1049, 2013. First published July 19, 2013 doi:10.1152/ajpheart.00194.2013.-The individual effects of estrogen and progesterone on baroreflex function remain poorly understood. We sought to determine how estradiol (E 2) and progesterone (P 4) independently alter the carotid-cardiac and carotid-vasomotor baroreflexes in young women by using a hormone suppression and exogenous add-back design. Thirty-two young women were divided into two groups and studied under three conditions: 1) after 4 days of endogenous hormone suppression with a gonadotropin releasing hormone antagonist (control condition), 2) after continued suppression and 3 to 4 days of supplementation with either 200 mg/day oral progesterone (N ϭ 16) or 0.1 to 0.2 mg/day transdermal 17␤-estradiol (N ϭ 16), and 3) after continued suppression and 3 to 4 days of supplementation with both hormones. Changes in heart rate (HR), mean arterial pressure (MAP), and femoral vascular conductance (FVC) were measured in response to 5 s of ϩ50 mmHg external neck pressure to unload the carotid baroreceptors. Significant hormone effects on the change in HR, MAP, and FVC from baseline at the onset of neck pressure were determined using mixed model covariate analyses accounting for P 4 and E2 plasma concentrations. Neither P4 (P ϭ 0.95) nor E2 (P ϭ 0.95) affected the HR response to neck pressure. Higher P 4 concentrations were associated with an attenuated fall in FVC (P ϭ 0.01), whereas higher E 2 concentrations were associated with an augmented fall in FVC (P ϭ 0.02). Higher E 2 was also associated with an augmented rise in MAP (P ϭ 0.01). We conclude that progesterone blunts whereas estradiol enhances carotidvasomotor baroreflex sensitivity, perhaps explaining why no differences in sympathetic baroreflex sensitivity are commonly reported between low and high combined hormone phases of the menstrual cycle. menstrual cycle; hormones; estrogen; arterial baroreceptors; blood pressure BOTH THE CARDIOVAGAL AND SYMPATHETIC branches of the baroreflex are important for the short-term control of blood pressure. Clear differences in cardiovagal and sympathetic baroreflex sensitivity have been documented between men and women (1,2,26,42,43), and women experience higher rates of orthostatic hypotension compared with men (7, 32, 39). Furthermore, the incidence of hypertension and cardiovascular disease is greatly increased in woman after menopause (23). These data provide evidence that the female sex hormones, estrogen and progesterone, influence the cardiovascular system; however, these influences are still poorly understood.In young women, the cardiovascular effects of the female sex hormones have predominantly been studied across the natural menstrual cycle. The majority of studies have found no differences in both ...

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