Murai I, Reichlin S, Ben-Jonathan N
Department of Physiology and Biophysics, Indiana University School of Medicine, Indianapolis 46223.
Endocrinology. 1989 Feb;124(2):1050-5. doi: 10.1210/endo-124-2-1050.
The proestrous surge of PRL could result from a decrease in dopamine, an increase in PRL-releasing factor (PRF) or both. The objectives were to determine whether PRF from the posterior pituitary regulates the proestrous PRL surge, and to examine if there are interactions between PRF and vasoactive intestinal peptide (VIP). Posterior pituitary lobectomy (LOBEX) and passive immunization against VIP were employed. Adult cycling rats were subjected at 0900 h on proestrus to LOBEX or sham surgery (SHAM) under short term anesthesia, and were injected iv at 1330 h with 0.75 ml anti-VIP serum or normal rabbit serum. Jugular blood was collected hourly from 1400-2300 h and analyzed for PRL and LH by RIA. Oviductal ova were examined on estrus. The rise in plasma PRL in normal rabbit serum-treated SHAM rats was biphasic, with an early peak between 1500-1700 h and a lower plateau between 1900-2100 h. This rise was similar in profile and magnitude to that seen in intact rats. In contrast, LOBEX significantly attenuated the early peak, but did not alter the plateau. Passive immunization against VIP of either SHAM or LOBEX rats mimicked the effect of LOBEX alone on PRL release. Neither surgery nor anti-VIP serum affected the profile of the LH surge which was sharp and symmetrical, and all rats ovulated with 15-16 ova per rat. To determine whether VIP is the posterior pituitary PRF, selected tissues removed on proestrus or diestrus-1 were analyzed for VIP by RIA. VIP was undetectable (less than 20 pg/organ) in the posterior pituitary on either day examined. The contents of VIP in the anterior pituitary, medial basal hypothalamus, and paraventricular nuclei were unchanged between diestrus-1 and proestrus.
The proestrous surge of PRL consists of two components: an early peak and a late plateau. The peak phase appears to be dependent on PRF input from the posterior pituitary. This input might be regulated by VIP, and interactions between the two could occur at the level of the hypothalamus, anterior pituitary, or both. The plateau phase of the PRL surge is independent of the posterior pituitary and VIP, and might involve hypothalamic dopamine.
促卵泡期催乳素（PRL）高峰可能是由于多巴胺减少、催乳素释放因子（PRF）增加或两者共同作用所致。目的是确定来自垂体后叶的PRF是否调节促卵泡期PRL高峰，并研究PRF与血管活性肠肽（VIP）之间是否存在相互作用。采用了垂体后叶切除术（LOBEX）和针对VIP的被动免疫。成年发情周期的大鼠在促卵泡期09:00接受短期麻醉下的LOBEX或假手术（SHAM），并于13:30静脉注射0.75 ml抗VIP血清或正常兔血清。从14:00至23:00每小时采集颈静脉血，通过放射免疫分析（RIA）检测PRL和促黄体生成素（LH）。在发情期检查输卵管卵子。正常兔血清处理的SHAM大鼠血浆PRL升高呈双相性，在15:00 - 17:00有一个早期高峰，在19:00 - 21:00有一个较低的平台期。这种升高在曲线和幅度上与完整大鼠相似。相比之下，LOBEX显著减弱了早期高峰，但未改变平台期。对SHAM或LOBEX大鼠进行针对VIP的被动免疫模拟了单独LOBEX对PRL释放的影响。手术和抗VIP血清均未影响LH高峰的曲线，LH高峰尖锐且对称，所有大鼠排卵，每只大鼠有15 - 16个卵子。为了确定VIP是否为垂体后叶PRF，对促卵泡期或动情间期 - 1切除的选定组织通过RIA分析VIP。在所检查的任何一天，垂体后叶中均未检测到VIP（低于20 pg/器官）。在动情间期 - 1和促卵泡期之间，垂体前叶、内侧基底部下丘脑和室旁核中的VIP含量未发生变化。
促卵泡期PRL高峰由两个部分组成：一个早期高峰和一个晚期平台期。高峰阶段似乎依赖于来自垂体后叶的PRF输入。这种输入可能受VIP调节，两者之间的相互作用可能发生在下丘脑、垂体前叶或两者水平。PRL高峰的平台期独立于垂体后叶和VIP，可能涉及下丘脑多巴胺。
