Hypothalamic and pituitary sites of action of oxytocin to alter prolactin secretion in the rat.
Hypothalamic and pituitary sites of action of oxytocin to alter prolactin secretion in the rat.
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DOI：
10.1210/endo-112-5-1711
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发表时间：
1983-05
期刊：
影响因子：
4.8
通讯作者：
M. Lumpkin;W. Samson;S. Mccann
中科院分区：
文献类型：
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作者：
M. Lumpkin;W. Samson;S. Mccann
为了确定催产素(OT)是否能改变垂体前叶催乳素(PRL)等激素的释放，在两个体外和两个体内实验系统上观察了催产素的作用。在两个实验中，将正常成年雄性大鼠垂体前叶分散的细胞培养在含有10(-8)、10(-7)、10(-6)和10(-5)M的OT的培养液中。在10(-8)和10(-7)M剂量下，催乳素的释放分别是对照组的1.5倍(P<0.01)和2~3倍(P<0.001)，表现出剂量依赖关系。更高的剂量不会产生高于10(-7)M OT的进一步升高。精氨酸加压素(AVP)引起分散细胞PRL释放的轻微减少，而TRH引起PRL释放的少量(25%)显著增加，但与剂量无关。成年雄性大鼠的半身腺与10(-6)和10(-5)M催乳素孵育后，分泌的催乳素是对照组的两倍(P<0.01)，但10(-7)M催产素的作用不明显。清醒雄性大鼠静脉注射1或10微克催乳素后，血浆催乳素水平仅在5min时较基础值升高50%(P<0.001)或500%(P<0.05)。赋形剂或0.1微克OT无效。清醒雄性大鼠第三脑室(3V)注射0.1微克催乳素后，血浆催乳素水平在30min时下降40%(P<0.001)，而1微克催产素在5~60min时显著降低，30min时下降幅度最大(60%，P<0.001)。这些发现可能表明存在一种超短环反馈机制，即外源性OT减少下丘脑OT的分泌，从而减少OT对PRL释放的刺激。OT对PRL影响的特异性通过OT未能显著改变每个系统中的FSH、LH和TSH来证明。GH无明显变化，但注射OT(仅1微克)可使血浆GH在15-30分钟升高(P<0.001)。这些结果支持这样的观点，即OT在低剂量到高剂量时直接作用于垂体前叶细胞，以剂量相关的方式特异性地释放催乳素。相反，3V注射OT减少了PRL的分泌，从而提示OT可能通过超短环反馈减少自身的神经分泌，从而减少OT对PRL释放的刺激。
To determine whether oxytocin (OT) could alter the release of PRL and other hormones from the anterior pituitary gland, the effects of OT were examined in two in vitro and two in vivo test systems. Cells dispersed from anterior pituitary glands of intact adult male rats were incubated in medium containing OT at doses of 10(-8), 10(-7), 10(-6), and 10(-5) M in two trials. OT stimulated PRL release 1.5-fold (P less than 0.01) and 2- to 3-fold (P less than 0.001) above control levels at 10(-8) and 10(-7) M doses, respectively, thus indicating a dose-dependent relationship. Higher doses did not produce a further elevation above that obtained with 10(-7) M OT. Arginine vasopressin (AVP) caused a slight decrease in PRL release from dispersed cells while TRH produced a small (25%), significant, but nondose-related increase in PRL release. Hemipituitary glands from adult male rats, incubated with 10(-6) and 10(-5) M OT, released twice as much PRL (P less than 0.01) into the medium as paired controls, but 10(-7) M OT was ineffective. The iv injection of 1 or 10 micrograms OT into conscious male rats elevated plasma PRL by 50% (P less than 0.05) or 500% (P less than 0.001), respectively, above basal values at 5 min only. Vehicle or 0.1 microgram OT were without effect. When 0.1 microgram OT was microinjected into the third ventricle (3V) of conscious male rats, it paradoxically reduced plasma PRL by 40% at 30 min (P less than 0.05), whereas 1 microgram OT significantly lowered PRL at 5-60 min, with the maximum suppression (60%, P less than 0.001) occurring at 30 min. These latter findings may indicate that an ultrashort loop feedback mechanism exists whereby exogenous OT decreases hypothalamic OT secretion, thereby reducing the OT stimulus for PRL release. The specificity of the OT effect on PRL was attested to by the failure of OT to alter significantly FSH, LH, and TSH in each system. GH was unchanged except that 3V-injected OT (1 microgram only) elevated (P less than 0.001) plasma GH at 15-30 min. These results support the view that OT acts directly on the cells of the anterior pituitary gland at low to high doses to release PRL specifically and in a dose-related fashion. In contrast, 3V injection of OT reduces PRL secretion, thereby suggesting that OT may decrease its own neurosecretion by ultrashort loop feedback and thus reduce an OT stimulus for PRL release.