Individual corpora lutea (CL) of Göttinger miniature pigs were implanted with an in vivo microdialysis system. This system functions like an artificial capillary, allowing diffusion of intraluteally secreted substances into the lumen of the dialysis system and administration of hormones into individual CL and simultaneous measurement of the response. After surgery the sows are fully awake and unrestrained. In the present study the in vivo release rates and secretion dynamics of progesterone (P) and oxytocin (OXT) were investigated. The dialysis system was implanted at day 2-4 of the estrous cycle, and dialysis experiments were performed throughout the next 3 days. Fractions were collected at 30 min intervals, and the concentrations of P and OXT were measured by RIA. Three major observations were made: Spontaneous intraluteal secretion of P and OXT occurred in a pulsatile manner. OXT secretion episodes in individual CL often coincide, indicating a simultaneous release from many CL of one ovary but also from the CL located in the contralateral ovary. OXT episodes also often coincide with P pulses; statistical evaluation revealed a significant correlation between P and OXT secretion. Intraluteal application of OXT stimulated luteal P and estradiol (E2) release in a dose-dependent manner. E2 added to the perfusates was also stimulatory to P release. The stimulation of P release by OXT could be antagonized by prior treatment of the CL with tamoxifen. We demonstrate for the first time in vivo the secretion of OXT from porcine CL. The microdialysis system enabled us to collect samples at the site of steroid and peptide release, i.e. within the intact luteal tissue. Our results suggest a stimulatory effect of OXT on P release from young and middle-aged CL and are in marked contrast to the previously demonstrated inhibitory effect of OXT on P release when luteal cells were cultured in vitro. A possible explanation for this apparent discrepancy is that OXT stimulates intraluteal release of E2, which is a powerful P releasing hormone, overcoming the direct inhibitory effect of OXT. This suggestion is substantiated by the observation that E2, when added to the perfusion medium, indeed stimulated P release.

译文

将g ö ttinger小型猪的个体黄体 (CL) 植入体内微透析系统。该系统的功能类似于人工毛细管,可将内部分泌的物质扩散到透析系统的内腔中,并将激素施用到单个CL中,并同时测量响应。手术后,母猪完全清醒,奔放。在本研究中,研究了孕酮 (P) 和催产素 (OXT) 的体内释放速率和分泌动力学。在发情周期的第2-4天植入透析系统,并在接下来的3天内进行透析实验。每隔30分钟收集一次馏分,并通过RIA测量P和OXT的浓度。进行了三个主要观察: P和OXT的自发内分泌以脉动方式发生。单个CL中的OXT分泌发作通常重合,表明一个卵巢的许多CL同时释放,也同时释放位于对侧卵巢的CL。OXT发作通常也与P脉冲同时发生; 统计评估显示P和OXT分泌之间存在显着相关性。OXT的体内应用以剂量依赖性方式刺激黄体P和雌二醇 (E2) 释放。添加到灌注液中的E2也刺激了P的释放。通过事先用他莫昔芬处理CL可以拮抗OXT对P释放的刺激。我们首次在体内证明了猪CL分泌OXT。微透析系统使我们能够在类固醇和肽释放的部位,即完整的黄体组织内收集样品。我们的结果表明OXT对年轻和中年CL释放P的刺激作用,与先前证明的体外培养黄体细胞时OXT对P释放的抑制作用形成鲜明对比。这种明显差异的可能解释是,OXT刺激E2的体内释放,而E2是一种强大的P释放激素,克服了OXT的直接抑制作用。观察到E2添加到灌注介质中时确实会刺激P释放,从而证实了这一建议。

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