Yallampalli C, Dong Y L
Departments of Obstetrics and Gynecology and Anatomy and Neurosciences, The University of Texas Medical Branch, Galveston, Texas 77555, USA.
Biol Reprod. 2000 Jul;63(1):34-41. doi: 10.1095/biolreprod63.1.34.
Nitric oxide (NO) is synthesized by NO synthases (NOS) from L-arginine in a variety of tissues, including rat uterus. Progesterone was shown to be required for maintaining elevated NOS II expression in pregnant rat uterus. However, effects of estrogens on uterine NOS II expression remains unclear. In the present study, we examined whether 17beta-estradiol regulates NO production and NOS II expression in the rat uterus during pregnancy and in nonpregnant rats treated with lipopolysaccharide (LPS). Rats on Day 18 of pregnancy received 17beta-estradiol (0.5 or 5 microgram/rat). Groups of ovariectomized (ovx) rats received 17beta-estradiol (5 microgram/rat) or LPS (1 mg/rat) or a combination of the two or received vehicle only. All rats were sacrificed 24 h after treatments. Nitrite concentrations in uterine cultures were measured by Greiss reaction. Uterine NOS II and NOS III proteins and mRNA levels were determined by Western blotting and reverse transcription polymerase chain reaction, respectively. In the pregnant rat, estradiol administration caused inhibition in total NO production, suppression of both mRNA and protein levels of NOS II enzyme, and increase in NOS III mRNA and protein levels in the uterus in a dose-dependent manner. The data indicate that estradiol inhibits NOS II and total NO generation and stimulates NOS III expression. In ovx rats, LPS stimulated NOS II mRNA and NO production by the uterus. Coadministration of 5 microgram estradiol profoundly suppressed NOS II mRNA and NO generation but elevated NOS III mRNA. Thus, estradiol inhibited LPS-induced increases in NOS II mRNA. Estradiol inhibits NO production by NOS II through the inhibition of NOS II expression in the rat uterus. This inhibition of NOS II expression occurs whether NOS II expression is constitutive (pregnancy) or induced (LPS-treated nonpregnant). Estradiol inhibition of NOS II expression occurs in the presence (pregnancy) or absence (ovx) of progesterone. Estradiol may play a role in regulating NOS II expression and NO production and uterine contractility during pregnancy and labor.
一氧化氮（NO）由一氧化氮合酶（NOS）在包括大鼠子宫在内的多种组织中，以L-精氨酸为原料合成。已表明孕酮是维持妊娠大鼠子宫中一氧化氮合酶II（NOS II）高表达所必需的。然而，雌激素对子宫NOS II表达的影响仍不清楚。在本研究中，我们检测了17β-雌二醇是否在妊娠期间以及在用脂多糖（LPS）处理的未孕大鼠中调节大鼠子宫中的NO生成和NOS II表达。妊娠第18天的大鼠接受17β-雌二醇（0.5或5微克/只大鼠）。去卵巢（ovx）大鼠组接受17β-雌二醇（5微克/只大鼠）或LPS（1毫克/只大鼠）或两者的组合，或仅接受溶剂。处理后24小时处死所有大鼠。通过格里斯反应测量子宫培养物中的亚硝酸盐浓度。分别通过蛋白质印迹法和逆转录聚合酶链反应测定子宫NOS II和NOS III蛋白及mRNA水平。在妊娠大鼠中，给予雌二醇导致子宫中总NO生成受到抑制，NOS II酶的mRNA和蛋白水平均受到抑制，且子宫中NOS III的mRNA和蛋白水平呈剂量依赖性增加。数据表明，雌二醇抑制NOS II和总NO生成，并刺激NOS III表达。在去卵巢大鼠中，LPS刺激子宫的NOS II mRNA和NO生成。同时给予5微克雌二醇可显著抑制NOS II mRNA和NO生成，但提高NOS III mRNA水平。因此，雌二醇抑制LPS诱导的NOS II mRNA增加。雌二醇通过抑制大鼠子宫中NOS II的表达来抑制NOS II产生的NO。无论NOS II表达是组成性的（妊娠）还是诱导性的（LPS处理的未孕大鼠），这种对NOS II表达的抑制都会发生。雌二醇对NOS II表达的抑制在有（妊娠）或无（去卵巢）孕酮的情况下都会发生。雌二醇可能在调节妊娠和分娩期间的NOS II表达、NO生成及子宫收缩中发挥作用。
