McNeill Anne Marie, Zhang Chunying, Stanczyk Frank Z, Duckles Sue P, Krause Diana N
Department of Pharmacology, College of Medicine, University of California at Irvine, CA 92697-4625, USA.
Stroke. 2002 Jun;33(6):1685-91. doi: 10.1161/01.str.0000016325.54374.93.
In vivo and in vitro rat models of hormone therapy were used to test the following hypotheses: (1) estrogen acts directly on cerebrovascular estrogen receptors to increase endothelial nitric oxide synthase (eNOS); (2) increased protein correlates with higher NOS activity; and (3) effects of estrogen on eNOS are altered by concurrent treatment with either medroxyprogesterone acetate (MPA) or progesterone.
Blood vessels were isolated from brains of ovariectomized female rats; some were treated for 1 month with estrogen, estrogen and progesterone, or estrogen and MPA. Isolated cerebral vessels were also treated in vitro with estrogen in the absence and presence of progesterone, MPA, tamoxifen, and the estrogen receptor antagonist ICI 182 780. Levels of eNOS were measured by Western blot, and NOS activity was measured by [14C]arginine-[14C]citrulline conversion.
Chronic hormone treatment in vivo resulted in plasma levels of 17beta-estradiol, progesterone, and MPA in the range of values found in humans. Estrogen treatment resulted in higher levels of cerebrovascular NOS activity that paralleled increases in eNOS protein. In vitro estrogen treatment for 18 hours also resulted in a concentration-dependent increase in eNOS protein (EC50 approximately 300 pmol/L) that was completely prevented by estrogen receptor antagonists tamoxifen or ICI 182 780. However, cotreatment with progesterone or MPA, either in vivo or in vitro, did not alter the effect of estrogen on eNOS protein.
Estrogen receptor activation in cerebrovascular tissue results in increased eNOS activity and protein levels. The latter effect persists in the presence of either progesterone or MPA. Thus, increased NO production by eNOS may contribute to the neuroprotective effects of estrogen.
利用体内和体外大鼠激素治疗模型来检验以下假设：（1）雌激素直接作用于脑血管雌激素受体以增加内皮型一氧化氮合酶（eNOS）；（2）蛋白质增加与较高的一氧化氮合酶（NOS）活性相关；（3）同时使用醋酸甲羟孕酮（MPA）或孕酮会改变雌激素对eNOS的作用。
从去卵巢雌性大鼠的大脑中分离血管；部分血管用雌激素、雌激素与孕酮或雌激素与MPA处理1个月。在体外，分离的脑血管在有或无孕酮、MPA、他莫昔芬和雌激素受体拮抗剂ICI 182 780的情况下用雌激素处理。通过蛋白质印迹法测量eNOS水平，通过[14C]精氨酸-[14C]瓜氨酸转化测量NOS活性。
体内慢性激素治疗导致血浆中17β-雌二醇、孕酮和MPA水平处于人类体内发现的值范围内。雌激素治疗导致脑血管NOS活性水平升高，这与eNOS蛋白增加平行。体外雌激素处理18小时也导致eNOS蛋白浓度依赖性增加（半数有效浓度约为300 pmol/L），这被雌激素受体拮抗剂他莫昔芬或ICI 182 780完全阻断。然而，无论在体内还是体外，同时使用孕酮或MPA均未改变雌激素对eNOS蛋白的作用。
脑血管组织中雌激素受体激活导致eNOS活性和蛋白水平增加。在存在孕酮或MPA的情况下，后一种作用持续存在。因此，eNOS产生的一氧化氮增加可能有助于雌激素的神经保护作用。
