Abstract
Background: β-adrenergic receptors play an important role in mitigating the pressor effects of sympathetic nervous system activity in young women. Based on recent data showing oral contraceptive use in women abolishes the relationship between muscle sympathetic nervous system activity and blood pressure, we hypothesized forearm blood flow responses to a β-adrenergic receptor agonist would be greater in young women currently using oral contraceptives (OC+, n = 13) when compared to those not using oral contraceptives (OC–, n = 10).Methods: Women (18–35 years) were studied during the early follicular phase of the menstrual cycle (days 1–5) or placebo phase of oral contraceptive use. Forearm blood flow (FBF, Doppler ultrasound) and mean arterial blood pressure (MAP, brachial arterial catheter) were measured at baseline and during graded brachial artery infusion of the β-adrenergic receptor agonist, Isoproterenol (ISO), as well as Acetylcholine (ACH, endothelium-dependent vasodilation) and Nitroprusside (NTP, endothelium-independent vasodilation). Forearm vascular conductance was calculated (FVC = FBF/MAP, ml/min/100 mmHg) and the rise in FVC from baseline during infusion quantified vasodilation (ΔFVC = FVCinfusion − FVCbaseline).Results: ISO increased FVC in both groups (p < 0.01) and ISO-mediated ΔFVC was greater in OC+ compared to OC– (Main effect of group, p = 0.02). Expressing data as FVC and FBF resulted in similar conclusions. FVC responses to both ACH and NTP were also greater in OC+ compared to OC–.Conclusions: These data are the first to demonstrate greater β-adrenergic receptor-mediated vasodilation in the forearm of women currently using oral contraceptives (placebo phase) when compared to those not using oral contraceptives (early follicular phase), and suggest oral contraceptive use influences neurovascular control.
Highlights
80% of American women will use oral contraceptives in their lifetimes (Shufelt and Bairey Merz, 2009; Boldo and White, 2011; Maguire and Westhoff, 2011)
Oral contraceptive use has been linked to improved vascular function, including increases in endothelial dependent vasodilation (Simoncini et al, 2007; Meendering et al, 2010), there are consistent reports that women using oral contraceptive pills exhibit higher systemic blood pressure (Narkiewicz et al, 1995; Cardoso et al, 1997; Boldo and White, 2011; Brito et al, 2011; Maguire and Westhoff, 2011)
Based on recent data showing oral contraceptive use in women abolishes the relationship between muscle sympathetic nervous system activity and blood pressure when assessed during the early follicular/placebo pill phase (Harvey et al, 2015), we hypothesized β-adrenergic receptor mediated vasodilation would be greater in young, healthy women using oral contraceptives when compared to those not currently using oral contraceptives
Summary
80% of American women will use oral contraceptives in their lifetimes (Shufelt and Bairey Merz, 2009; Boldo and White, 2011; Maguire and Westhoff, 2011). Oral contraceptive use has been linked to improved vascular function, including increases in endothelial dependent vasodilation (Simoncini et al, 2007; Meendering et al, 2010), there are consistent reports that women using oral contraceptive pills exhibit higher systemic blood pressure (Narkiewicz et al, 1995; Cardoso et al, 1997; Boldo and White, 2011; Brito et al, 2011; Maguire and Westhoff, 2011). Young men exhibit a positive relationship between sympathetic nervous system activity and total peripheral resistance (Hart et al, 2011). This relationship, is only observed in young women following β-adrenoceptor blockade (Hart et al, 2011). With this information in mind, we sought to examine the effect of current oral contraceptive use on β-adrenergic receptor mediated vasodilation using an isolated forearm model. Based on recent data showing oral contraceptive use in women abolishes the relationship between muscle sympathetic nervous system activity and blood pressure when assessed during the early follicular/placebo pill phase (Harvey et al, 2015), we hypothesized β-adrenergic receptor mediated vasodilation would be greater in young, healthy women using oral contraceptives (placebo phase) when compared to those not currently using oral contraceptives (early follicular phase)
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