Chao C C, Moss G E, Malven P V
Life Sci. 1986 Aug 11;39(6):527-34. doi: 10.1016/0024-3205(86)90509-6.
Although endogenous opioid peptides (EOP) are thought to alter pituitary release of luteinizing hormone (LH) by modifying the release of gonadotropin-releasing hormone (GnRH) from the brain, EOP may also directly affect the release of LH from pituitary cells. This hypothesis was tested using dispersed cells from the bovine anterior pituitary gland. Pituitaries were enzymatically dissociated, preincubated for 18 h and then cultured for either 2 or 24 h with GnRH, naloxone, methionine-enkephalin (Met-enk) or their combinations. Basal release of LH into media was 18.2 and 38.4 ng/100,000 cells after culture for 2 or 24 h, respectively. When cultured for 2 or 24 h with 10 nM GnRH, LH release was 296% and 131% of the basal release for each culture period. Cellular viability (75% vs 68%) and total (cells + medium) LH (128 vs 134 ng/100,000 cells) did not differ (P greater than .05) between cells cultured for 2 or 24 h. Naloxone (1 microM) increased (P less than .01) basal release of LH by 57% after 2 h of culture but not after 24 h of culture. Naloxone did not augment the amount of LH released in response to 10 nM GnRH. Addition of Met-enk (1 nM to 1 microM) suppressed (P less than .05) basal release of LH (23% to 62%) after 2 h of culture. Similar suppressive effects (8% to 49%) occurred in a dose-dependent manner (0.1 nM to 1 microM) after 24 h of culture. Met-enk (1 and 100 nM) antagonized (P less than .05) the stimulatory effect of naloxone and reduced (P less than .05) the amount of LH released in response to GnRH after 2 h of culture. In summary, the stimulatory effect of naloxone on the basal release of LH suggests that EOP may directly regulate pituitary cell function; the inhibitory effect of physiological concentrations of Met-enk on the basal in vitro release of LH suggests that EOP may directly affect the release of LH in vivo; the antagonism between the stimulatory effect of naloxone and the inhibitory effect of Met-enk is consistent with effects exerted through opioid receptors; and the stimulatory effect of GnRH may be partially reduced by Met-enk. These results are consistent with the hypothesis that opioids may directly modulate the release of LH at the pituitary level.
虽然内源性阿片肽（EOP）被认为通过改变促性腺激素释放激素（GnRH）从大脑的释放来改变垂体促黄体生成素（LH）的释放，但EOP也可能直接影响垂体细胞LH的释放。本研究使用牛垂体前叶分散细胞对该假说进行了验证。将垂体用酶解离，预孵育18小时，然后用GnRH、纳洛酮、甲硫氨酸脑啡肽（Met-enk）或它们的组合培养2或24小时。培养2或24小时后，LH向培养基中的基础释放量分别为18.2和38.4 ng/100,000个细胞。当用10 nM GnRH培养2或24小时时，每个培养期LH的释放量分别为基础释放量的296%和131%。培养2或24小时的细胞之间的细胞活力（75%对68%）和总LH（细胞+培养基，128对134 ng/100,000个细胞）没有差异（P大于0.05）。纳洛酮（1 microM）在培养2小时后增加（P小于0.01）LH的基础释放量57%，但在培养24小时后没有增加。纳洛酮没有增强对10 nM GnRH反应时LH的释放量。添加Met-enk（1 nM至1 microM）在培养2小时后抑制（P小于0.05）LH的基础释放量（23%至62%）。培养24小时后，类似的抑制作用（8%至49%）以剂量依赖性方式（0.1 nM至1 microM）出现。Met-enk（1和100 nM）在培养2小时后拮抗（P小于0.05）纳洛酮的刺激作用，并减少（P小于0.05）对GnRH反应时LH的释放量。总之，纳洛酮对LH基础释放的刺激作用表明EOP可能直接调节垂体细胞功能；生理浓度的Met-enk对体外LH基础释放的抑制作用表明EOP可能直接影响体内LH的释放；纳洛酮的刺激作用与Met-enk的抑制作用之间的拮抗作用与通过阿片受体发挥的作用一致；GnRH的刺激作用可能部分被Met-enk降低。这些结果与阿片类物质可能在垂体水平直接调节LH释放的假说一致。
