Impact of estradiol blood concentrations on skin capillary Laser Doppler flow in premenopausal women

Abstract

Objective and method: Estradiols are known to prevent cardiovascular diseases, but the underlying mechanisms remain unclear. We assessed the finger skin capillary blood flow in 20 premenopausal women with oral contraception noninvasively by Laser Doppler flowmetry (LDF). Blood flow was registered both under basal conditions and after 2 min of arterial occlusion. Furthermore, the combination with a beat-to-beat online finger blood pressure monitor allowed the calculation of the regional peripheral resistance (RPR). All measurements were performed in the menstrual phase. LDF and RPR were correlated to the estradiol whole blood levels. Results: Both baseline ( r 2=0.826; P<0.01) and vasodilation ( r 2=0.747; P<0.01) blood flux were significantly correlated to the corresponding estradiol concentrations. A multiple stepwise regression analysis (with age, height, weight, duration of oral contraception, nicotine pack years and estradiol levels in the equation) showed positive correlations between estradiol levels and (a) baseline ( P<0.05) or (b) vasodilation ( P<0.05) Laser Doppler flux or (c) time to reach the peak flux ( r 2=0.31; P<0.05). Furthermore, the minimal local vascular resistance was negatively correlated to the estradiol levels ( r 2=0.45; P<0.05). Conclusion: The study provides evidence that both the baseline and the vasodilation capillary blood flux in women in the menstrual phase depend on the estradiol whole blood levels. Furthermore, the local vascular resistance shows a negative correlation to the hormonal state. Functional or structural alterations of the microvasculature may therefore contribute to the estradiol-associated cardiovascular protection.