Institute of Physiology, Center of Physiological Medicine, Medical University of Graz, Graz, Austria.
PLoS One. 2013 Aug 2;8(8):e71655. doi: 10.1371/journal.pone.0071655. eCollection 2013.
As the vascular endothelium has multiple functions, including regulation of vascular tone, it may play a role in the pathophysiology of orthostatic intolerance. We investigated the effect of orthostasis on endothelial function using EndoPAT®, a non-invasive and user-independent method, and across gender. As sex steroid hormones are known to affect endothelial function, this study examined the potential effect of these hormones on the endothelial response to orthostasis by including females at different phases of the menstrual cycle (follicular and luteal-where the hormone balance differs), and females taking an oral contraceptive. A total of 31 subjects took part in this study (11 males, 11 females having normal menstrual cycles and 9 females taking oral contraceptive). Each subject made two visits for testing; in the case of females having normal menstrual cycles the first session was conducted either 1-7 (follicular) or 14-21 days (luteal) after the start of menstruation, and the second session two weeks later, i.e., during the other phase, respectively. Endothelial function was assessed at baseline and following a 20-min orthostatic challenge (active standing). The EndoPAT® index increased from 1.71 ± 0.09 (mean ± SEM) at baseline to 2.07 ± 0.09 following orthostasis in females (p<0.001). In males, the index increased from 1.60 ± 0.08 to 1.94 ± 0.13 following orthostasis (p<0.001). There were no significant differences, however, in the endothelial response to orthostasis between females and males, menstrual cycle phases and the usage of oral contraceptive. Our results suggest an increased vasodilatatory endothelial response following orthostasis in both females and males. The effect of gender and sex hormones on the endothelial response to orthostasis appears limited. Further studies are needed to determine the potential role of this post orthostasis endothelial response in the pathophysiology of orthostatic intolerance.
由于血管内皮具有多种功能，包括调节血管张力，因此它可能在直立不耐受的病理生理学中发挥作用。我们使用非侵入性且独立于用户的 EndoPAT® 方法研究了体位对内皮功能的影响，并对两性进行了研究。由于已知性激素会影响内皮功能，因此这项研究通过纳入处于不同月经周期（激素平衡不同的卵泡期和黄体期）的女性以及服用口服避孕药的女性，检查了这些激素对直立后内皮反应的潜在影响。共有 31 名受试者参加了这项研究（11 名男性，11 名月经周期正常的女性和 9 名服用口服避孕药的女性）。每位受试者进行了两次测试；对于月经周期正常的女性，第一次测试在月经开始后第 1-7 天（卵泡期）或第 14-21 天（黄体期）进行，第二次测试在两周后，即分别处于另一个周期。在基线和 20 分钟的直立挑战（主动站立）后评估内皮功能。EndoPAT®指数从基线时的 1.71±0.09（平均值±SEM）增加到女性直立后的 2.07±0.09（p<0.001）。在男性中，指数从基线时的 1.60±0.08 增加到直立后的 1.94±0.13（p<0.001）。然而，女性与男性、月经周期阶段和口服避孕药的使用之间，直立后内皮反应没有显著差异。我们的结果表明，女性和男性在直立后均出现血管扩张性内皮反应增加。性别和性激素对直立后内皮反应的影响似乎有限。需要进一步的研究来确定这种直立后内皮反应在直立不耐受病理生理学中的潜在作用。
