Garcia M R, Amstalden M, Keisler D H, Raver N, Gertler A, Williams G L
Animal Reproduction Laboratory, Texas A&M University Agricultural Research Station, Hwy 59E, Beeville, TX 78102-9410, USA.
Domest Anim Endocrinol. 2004 Apr;26(3):189-200. doi: 10.1016/j.domaniend.2003.10.003.
We tested the hypothesis that recombinant ovine leptin would attenuate the acute effects of neuropeptide Y (NPY) on secretion of GH and gonadotropins (LH and FSH) in cows. Ovariectomized cows (n=6) fitted with third ventricle guide cannulas were assigned randomly to each of three groups in a Latin square arrangement: (1) control; saline treatment only, (2) NPY; saline followed by NPY, and (3) L-NPY; leptin pretreatment followed by NPY. Treatments were: s.c. injection of saline or leptin (30 microg/kg BW) at time 0, i.v. injection of saline or leptin (30 microg/kg BW) at 70 min, and intracerebroventricular (i.c.v.) injection of saline or NPY (500 microg) at 90 min. Plasma leptin was elevated (P<0.01) at least four-fold throughout the experiment in the L-NPY group. Mean plasma concentrations of LH declined within 1 h and were lower (P<0.03) than controls in both the NPY and L-NPY groups beginning 2 h after NPY injection. An acute increase in plasma concentrations of GH was observed within 1 h after NPY in the NPY group and mean values were greater (P<0.01) than controls. However, in the L-NPY group, leptin pretreatment attenuated the NPY effect on GH. Treatments had no effect on FSH secretion. Results confirm suppressive and stimulatory effects of NPY on LH and GH secretion, respectively, and indicate that leptin can attenuate the acute effects of NPY on GH secretion in cattle.
重组羊瘦素会减弱神经肽Y（NPY）对奶牛生长激素（GH）和促性腺激素（促黄体激素LH和促卵泡激素FSH）分泌的急性影响。将安装有第三脑室引导套管的去卵巢奶牛（n = 6）按照拉丁方设计随机分为三组：（1）对照组，仅进行生理盐水处理；（2）NPY组，先注射生理盐水再注射NPY；（3）L-NPY组，先进行瘦素预处理再注射NPY。处理方式如下：在0时刻皮下注射生理盐水或瘦素（30微克/千克体重），70分钟时静脉注射生理盐水或瘦素（30微克/千克体重），90分钟时脑室内注射生理盐水或NPY（500微克）。在整个实验过程中，L-NPY组的血浆瘦素水平升高了至少四倍（P<0.01）。在注射NPY后2小时开始，NPY组和L-NPY组的LH平均血浆浓度在1小时内下降，且低于对照组（P<0.03）。在NPY组中，注射NPY后1小时内观察到GH血浆浓度急性升高，平均值高于对照组（P<0.01）。然而，在L-NPY组中，瘦素预处理减弱了NPY对GH的影响。处理对FSH分泌没有影响。结果证实了NPY分别对LH和GH分泌具有抑制和刺激作用，并表明瘦素可以减弱NPY对奶牛GH分泌的急性影响。
