Estupina C, Pinter A, Belmar J, Astier H, Arancibia S
Laboratory of Neuroendocrinological Neurobiology, University of Montpellier, France.
Neuroendocrinology. 1996 Feb;63(2):181-7. doi: 10.1159/000126955.
To investigate the secretory pattern of somatostatin (SS) from the median eminence (ME) in the female rat, as well as estrogenic influence on this secretion, we measured both SS release and hypothalamic content in cycling, 10-day ovariectomized, and ovariectomized rats treated with estradiol for 3 days before. Animals were stereotaxically implanted with a push-pull cannula into the ME, and 10 days later the hypothalamic structure was perfused with artificial cerebrospinal fluid for 120-150 min at a regular flow rate of 17 mu l/min. Secretion peaks were observed in the pattern of SS release, whatever the stage of the estrous cycle. The mean amplitude of SS peaks was similar throughout the cycle: 11.7 +/- 4.0, 8.6 +/- 1.5 and 10.5 +/- 1.3 pg at proestrus, estrus and diestrus, respectively, and it was affected neither by ovariectomy (7.4 +/- 1.3 pg) nor by estrogen replacement (5.5 +/- 1.0 pg). By contrast, mean SS release levels in the proestrus phase were significantly higher than those measured in the other phases: 21.6 +/- 2.1 vs. 17.7 +/- 1.2 pg/15 min in diestrus (p < 0.05) and vs. 12.0 +/- 0.7 pg/15 min in estrus (p < 0.001). Hypothalamic SS content showed variations quite similar to those observed during its release, i.e. with the highest values corresponding to the proestrus phase (1,170.5 +/- 224.9 pg/mg of tissue) and to the diestrus (1,156.5 +/- 332.1 pg/mg of tissue) and the lowest values in the estrus (511.5 +/- 52.9 pg/mg of tissue; p < 0.05 vs. proestrus and diestrus). In addition, the lowest SS content and secretion values were found in ovariectomized animals: 95.5 +/- 5.1 pg/mg of tissue (p < 0.001 compared to the values obtained for each stage of the estrous cycle) and 10.0 +/- 0.9 pg/15 min (p < 0.001 vs. proestrus and diestrus), respectively. Patterns of SS release and SS hypothalamic content were not modified by estradiol treatment in ovariectomized animals. Our results suggest that (1) whatever the stage of the estrous cycle, SS release from the ME is not uniform and exhibits irregular peaks; (2) mean SS release levels were subjected to gonadal influence; (3) the occurrence of SS peaks seems to be estrogen-independent, and (4) variations in hypothalamic SS content were generally in good agreement with those of neurohormone release.
为研究雌性大鼠正中隆起（ME）中生长抑素（SS）的分泌模式以及雌激素对该分泌的影响，我们测定了处于发情周期的大鼠、卵巢切除10天的大鼠以及术前3天接受雌二醇治疗的卵巢切除大鼠的SS释放量和下丘脑含量。将动物通过立体定位法在ME处植入推挽式套管，10天后以17μl/分钟的恒定流速用人工脑脊液灌注下丘脑结构120 - 150分钟。无论发情周期处于哪个阶段，在SS释放模式中均观察到分泌峰值。整个周期中SS峰值的平均幅度相似：在发情前期、发情期和动情间期分别为11.7±4.0、8.6±1.5和10.5±1.3 pg，其既不受卵巢切除（7.4±1.3 pg）影响，也不受雌激素替代（5.5±1.0 pg）影响。相比之下，发情前期的平均SS释放水平显著高于其他阶段：动情间期为21.6±2.1 pg/15分钟，而发情期为17.7±1.2 pg/15分钟（p < 0.05），发情期为12.0±0.7 pg/15分钟（p < 0.001）。下丘脑SS含量的变化与释放过程中观察到的变化非常相似，即最高值对应发情前期（1,170.5±224.9 pg/mg组织）和动情间期（1,156.5±332.1 pg/mg组织），发情期最低（511.5±52.9 pg/mg组织；与发情前期和动情间期相比，p < 0.05）。此外，在卵巢切除的动物中发现SS含量和分泌值最低：分别为95.5±5.1 pg/mg组织（与发情周期各阶段获得的值相比，p < 0.001）和10.0±0.9 pg/15分钟（与发情前期和动情间期相比，p < 0.001）。在卵巢切除的动物中，雌二醇处理并未改变SS释放模式和下丘脑SS含量。我们的结果表明：（1）无论发情周期处于哪个阶段，ME中SS的释放都不均匀且呈现不规则峰值；（2）SS平均释放水平受性腺影响；（3）SS峰值的出现似乎与雌激素无关；（4）下丘脑SS含量的变化通常与神经激素释放的变化高度一致。
