Novaro V, González E, Jawerbaum A, Rettori V, Canteros G, Gimeno M F
Centro de Estudios Farmacológicos y Botánicos, CONICET, Buenos Aires, Argentina.
Reprod Fertil Dev. 1997;9(5):557-64. doi: 10.1071/r97005.
It has previously been demonstrated that uterine nitric oxide synthase (NOS) activity increases before embryonic implantation in rats. The aim of the present work was to investigate the regulation and the physiological relevance of the nitric oxide (NO) system in ovoimplantation. The increase in NOS activity in early pregnancy was found to be independent of the presence of embryos in the uterus. Whereas the Ca2+-dependent isoform of NOS increased gradually in the preimplantation days, the Ca2+-independent isoform increased just at the beginning of implantation (Day 5, 1800 hours); then the activity of both isoforms declined. Oestradiol, whose concentration peaks before implantation, might be regulating NOS activity in the uterus, since treatment of rats with tamoxifen, a receptor antagonist, reduces the activity of both isoforms to preimplantation levels. Intraluminal injections of L-NAME (0.5 mg kg[-1]), a competitive inhibitor of NOS, reduced by 50% the number of implanted embryos; this suggests that the NO system plays a role during implantation. The data suggest that oestradiol might be a modulator of NOS activity during nidation and that NO production is necessary to achieve a successful embryo implantation.
先前已经证明，大鼠胚胎着床前子宫一氧化氮合酶（NOS）活性会增加。本研究的目的是探讨一氧化氮（NO）系统在卵着床过程中的调节作用及其生理相关性。研究发现，妊娠早期NOS活性的增加与子宫内胚胎的存在无关。在着床前的几天里，依赖钙的NOS同工型逐渐增加，而不依赖钙的同工型在着床开始时（第5天，18:00）才增加；然后两种同工型的活性均下降。在着床前浓度达到峰值的雌二醇可能在调节子宫中的NOS活性，因为用受体拮抗剂他莫昔芬处理大鼠会使两种同工型的活性降低到着床前水平。向子宫腔内注射NOS的竞争性抑制剂L-NAME（0.5 mg kg[-1]）可使着床胚胎数量减少50%；这表明NO系统在着床过程中发挥作用。数据表明，雌二醇可能是着床期间NOS活性的调节剂，并且产生NO是成功实现胚胎着床所必需的。
