Kanyicska B, Nguyen D N, Arey B J, Freeman M E
Department of Biological Science, Florida State University, Tallahasse 32306.
Endocrinology. 1990 Apr;126(4):2021-6. doi: 10.1210/endo-126-4-2021.
The contribution of the uterus to the regulation of PRL secretion in lactating dams and cycling female rats was investigated. Lactating animals were hysterectomized or sham operated 2 days after parturition, and the number of pups was adjusted to eight. Blood samples for PRL RIA were obtained through intra-atrial cannulae implanted 2 days before experimentation. In order to study the PRL secretory profile in undisturbed freely lactating rats, blood samples were taken every 2 h for 24 h starting at 1400 h. During early lactation (days 7-8), hysterectomy did not alter the PRL secretory profile compared to that of sham-operated controls. On days 14-15 post partum, PRL secretion followed a characteristic bimodal pattern showing two PRL surges at 1800 h and 0600 h. After hysterectomy, the early morning PRL surge disappeared and PRL secretion showed an unimodal daily rhythm reaching its peak at 1800 h. The possible effect of the absence of the uterus on suckling-induced PRL release at various stages of lactation was studied. On days 7-8, suckling stimuli after 4 h of pup deprivation induced robust PRL release. Hysterectomy did not significantly alter PRL release at this earlier stage of lactation. In control groups, the suckling-induced PRL secretory response markedly declined as the postpartum period advanced. On the other hand, the hysterectomized animals retained significantly greater responsiveness to suckling during the second half of lactation. These data indicate an inhibitory influence of the uterus on PRL secretion. The onset of this uterine effect is considerably delayed, and its influence became prominent only at a later phase of lactation. The effect of length of pup deprivation preceding the suckling stimulus, in combination with hysterectomy, was also investigated. Hysterectomy significantly increased suckling-induced PRL release after 4 and 24 h separation compared to the sham-hysterectomized animals. When the separation was longer than 48 h, the inducibility of PRL release by suckling declined and was not influenced by hysterectomy. In order to study the possible influence of the uterus on PRL secretion during the estrous cycle, regularly cycling female rats were hysterectomized at diestrus 1. Twelve days later the animals were cannulated, and serial blood samples were taken during the subsequent proestrus. Hysterectomy did not alter the PRL surge which occurred on the afternoon of proestrus indicating that the uterus does not have a major function in regulating PRL secretion on proestrus. In conclusion, hysterectomy significantly delayed the extinction of suckling-induced PRL release revealing the active role of the uterus in the regulation of this neuroendocrine reflex.
研究了子宫对泌乳母鼠和性周期正常的雌性大鼠催乳素（PRL）分泌调节的作用。泌乳动物在产后2天进行子宫切除术或假手术，并将幼崽数量调整为8只。在实验前2天通过植入心房套管采集用于PRL放射免疫分析（RIA）的血样。为了研究未受干扰的自由泌乳大鼠的PRL分泌模式，从14:00开始，每2小时采集一次血样，共采集24小时。在泌乳早期（第7 - 8天），与假手术对照组相比，子宫切除术并未改变PRL分泌模式。在产后第14 - 15天，PRL分泌呈现出特征性的双峰模式，在18:00和06:00出现两个PRL分泌高峰。子宫切除术后，清晨的PRL分泌高峰消失，PRL分泌呈现单峰日节律，在18:00达到峰值。研究了子宫缺失对泌乳不同阶段哺乳诱导的PRL释放的可能影响。在第7 - 8天，幼崽剥夺4小时后的哺乳刺激诱导了强烈的PRL释放。在泌乳早期，子宫切除术并未显著改变PRL释放。在对照组中，随着产后时间的推移，哺乳诱导的PRL分泌反应明显下降。另一方面，子宫切除的动物在泌乳后期对哺乳的反应性显著更高。这些数据表明子宫对PRL分泌有抑制作用。这种子宫效应的开始明显延迟，其影响仅在泌乳后期才变得显著。还研究了哺乳刺激前幼崽剥夺时间长短与子宫切除术相结合的影响。与假子宫切除的动物相比，子宫切除术后，在分离4小时和24小时后，哺乳诱导的PRL释放显著增加。当分离时间超过48小时时，哺乳诱导PRL释放的诱导性下降，且不受子宫切除术的影响。为了研究子宫对发情周期中PRL分泌的可能影响，在动情间期1对性周期正常的雌性大鼠进行子宫切除术。12天后对动物进行插管，并在随后的动情前期采集系列血样。子宫切除术并未改变动情前期下午出现的PRL分泌高峰，表明子宫在调节动情前期PRL分泌方面没有主要作用。总之，子宫切除术显著延迟了哺乳诱导的PRL释放的消退，揭示了子宫在调节这种神经内分泌反射中的积极作用。
