Borowiec Monika, Wasilewska-Dziubiñska Elzbieta, Chmielowska Magdalena, Woliñska-Witort Ewa, Baranowska Boguslawa
Neoruoendocrinology Department, Medical Centre of Postgraduate Education, Fieldorfa 40, 04-158 Warsaw, Poland.
Neuro Endocrinol Lett. 2002 Apr;23(2):149-54.
The aim of this study was to investigate the influence of NMMA on the mechanism of leptin and NPY action in in vivo and in vitro on pituitary hormone release by female rats in diestrus.
In vivo experiments based on four-day ip injections of: 1) murine recombinant leptin (mrLep); 2) human NPY; 3) saline; 4) NMMA (50 microg) was applied prior to administration of mrLep; 5) NMMA (50 microg) was applied prior to administration of NPY; 6) NMMA (50 microg); 7) NMMA (350 microg) was applied prior to administration of mrLep; 8) NMMA (350 microg). The blood samples for LH and FSH were collected after decapitation of animals on the fifth day of study. In vitro experiments studied the effects of these peptides on LH release from pituitary cell culture.
In vivo: Leptin+ NMMA (50 microg) stimulated LH. NPY+ NMMA (50 microg) increased LH. NMMA (350 microg) stimulated FSH release. In vitro: The stimulatory effect of leptin on LH release in vitro was observed after 120 min of incubation, but after 60 mins of incubation the inhibitory effect of leptin on LH release was increased by NMMA. Leptin +NMMA (vs NMMA) decreased LH release with highest statistical significance. NPY 10 nM 60 min after incubation decreased LH release. There was no effect of NMMA on LH release.
In vivo results show, that NO probably mediates in leptin action on LH release. Moreover, effects of leptin on LH release from cultured pituitary cells are dependent on time of incubation. NPY decreased LH release in vitro.
本研究旨在探讨N-甲基-D-天冬氨酸（NMMA）对处于动情间期的雌性大鼠体内和体外瘦素及神经肽Y（NPY）作用机制的影响，以及对垂体激素释放的影响。
进行体内实验，连续四天腹腔注射：1）小鼠重组瘦素（mrLep）；2）人NPY；3）生理盐水；4）在注射mrLep之前应用NMMA（50微克）；5）在注射NPY之前应用NMMA（50微克）；6）NMMA（50微克）；7）在注射mrLep之前应用NMMA（350微克）；8）NMMA（350微克）。在研究的第五天，动物断头后采集血液样本用于检测促黄体生成素（LH）和促卵泡生成素（FSH）。体外实验研究这些肽对垂体细胞培养物中LH释放的影响。
体内实验：瘦素+NMMA（50微克）刺激LH分泌。NPY+NMMA（50微克）使LH增加。NMMA（350微克）刺激FSH释放。体外实验：孵育120分钟后观察到瘦素对体外LH释放有刺激作用，但孵育60分钟后，NMMA增强了瘦素对LH释放的抑制作用。瘦素+NMMA（与NMMA相比）使LH释放减少，具有最高的统计学意义。孵育60分钟后，10纳摩尔NPY使LH释放减少。NMMA对LH释放没有影响。
体内实验结果表明，一氧化氮（NO）可能介导了瘦素对LH释放的作用。此外，瘦素对培养的垂体细胞LH释放的影响取决于孵育时间。NPY在体外使LH释放减少。
