The effect of estrogen on blood pressure regulation during psychological stress and its mechanism

关于雌激素对应激诱导的压力反应的影响及其机制，我们得到了以下结果。(1)雌激素通过内皮型一氧化氮合酶（endothelial nitric oxide synthase, eNOS）的过表达减轻大鼠心理应激诱导的压力反应。遥测系统下自由活动大鼠中，雌性(F)组与雄性(M)组相比，压力反应倾向于被抑制。此外，与安慰剂治疗(P)组相比，卵巢切除雌激素治疗(E)组对笼子切换和约束压力的反应明显减弱。然而，预处理NOS抑制剂可减少应激诱导的压力反应在P组和E组之间的差异。与M、P组相比，E组肠系膜中eNOS的表达明显增强。提示雌激素可减轻心理应激诱导的应激反应，其作用机制可能与肠系膜eNOS过表达有关。(2)女性在月经周期中对精神压力的压力反应随血浆雌二醇水平的变化而变化。年轻女性月经期(M)和排卵前(O)期（YW）的静息血压（BP）无显著差异。颜色词试验（CWT）诱导的收缩压（SBP）和舒张压（DBF）在0期较m期略有降低，但不显著。静息血浆去甲肾上腺素（NE）在o期升高，cwt诱导的NE升高在o期有减弱的趋势。此外，绝经后妇女（PM）的静息DBF高于YW。在CWT期间，PM比YW的DBP显著且立即升高，并持续到恢复期的约15分钟。这些发现提示雌激素可以减轻女性精神压力引起的舒张压升高。

We obtained the following results on the effect of estrogen on stress-induced pressor responses and its mechanism.(1)Estrogen attenuates pressor responses induced by psychological stresses through endothelial nitric oxide synthase(eNOS) overexpression in rats.Pressor response to the cage-switch stress tended to be suppressed in the female (F) group compared with the male (M) group in free moving rats using the telemetry system. Furthermore, these responses to the cage-switch and restraint stresses were attenuated significantly in the ovariectomized estrogen-treated (E) group compared with the placebo-treated (P) group. However, pretreatment of NOS inhibitor diminished the difference of the stress-induced pressor response between the P and E groups. Moreover, the expression of eNOS in the mesentery enhanced significantly in the E group compared with the M and P groups. These results suggest that estrogen attenuates psychological stress-induced pressor responses and the mesenteric eNOS overexpression could explain the mechanism for its effect in rats.(2)Pressor response to mental stress varies during menstrual cycle depending on plasma estradiol levels in women.The resting blood pressure(BP) was not different between the menstrual (M) and the pre-ovulatory (O) phases of menstrual cycle in young women(YW). The elevations of systolic BP(SBP) and diastolic BP(DBF) induced by the Color Word Test(CWT) were slightly, but not significantly attenuated in O-phase compared with M-phase. In addition, the resting plasma norepinephrine(NE) was higher in O-phase, and its CWT-induced elevation tended to be attenuated in O-phase. Furthermore, the resting DBF was higher in postmenopausal women(PM) than YW. The significant and immediate elevation of DBP during the CWT was greater in PM than in YW and continued until about 15 min of the recovery period. These findings suggest that estrogen may attenuate the DBP elevations induced by the mental stress in women.