Shaham-Albalancy A, Folman Y, Kaim M, Rosenberg M, Wolfenson D
Department of Animal Science, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
Reproduction. 2001 Oct;122(4):643-8. doi: 10.1530/rep.0.1220643.
Low progesterone concentrations during the bovine oestrous cycle induce enhanced responsiveness to oxytocin challenge late in the luteal phase of the same cycle. The delayed effect of low progesterone concentrations during one oestrous cycle on uterine PGF(2alpha) secretion after oxytocin challenge on day 15 or 16 of the subsequent cycle was studied by measuring the concentrations of the major PGF(2alpha) metabolite (13,14-dihydro-15-keto PGF(2alpha); PGFM) in plasma. Two experiments were conducted, differing in the type of progesterone treatment and in the shape of the low progesterone concentration curves. In Expt 1, progesterone supplementation with intravaginal progesterone inserts, with or without an active corpus luteum, was used to obtain high, or low and constant plasma progesterone concentrations, respectively. In Expt 2, untreated cows, representing high progesterone treatment, were compared with cows that had low but increasing plasma progesterone concentrations that were achieved by manipulating endogenous progesterone secretion of the corpus luteum. Neither experiment revealed any differences in plasma progesterone concentrations between the high and low progesterone groups in the subsequent oestrous cycle. In both experiments, both groups had similar basal concentrations of PGFM on day 15 (Expt 1) or 16 (Expt 2) of the subsequent oestrous cycle, 18 days after progesterone treatments had ended. In both experiments, the increases in PGFM concentrations in the low progesterone groups after an oxytocin challenge were markedly higher than in the high progesterone groups. These results indicate that low progesterone concentrations during an oestrous cycle have a delayed stimulatory effect on uterine responsiveness to oxytocin during the late luteal phase of the subsequent cycle. This resulting increase in PGF(2alpha) secretion may interfere with luteal maintenance during the early stages of pregnancy.
牛发情周期中孕酮浓度较低会导致在同一周期黄体期后期对催产素刺激的反应性增强。通过测量血浆中主要前列腺素F2α代谢物（13,14-二氢-15-酮前列腺素F2α；PGFM）的浓度，研究了一个发情周期中孕酮浓度较低对后续周期第15天或16天催产素刺激后子宫前列腺素F2α分泌的延迟影响。进行了两项实验，孕酮处理类型和低孕酮浓度曲线形状有所不同。在实验1中，使用阴道内孕酮植入物补充孕酮，无论有无活性黄体，分别获得高或低且恒定的血浆孕酮浓度。在实验2中，将未处理的奶牛（代表高孕酮处理）与通过操纵黄体的内源性孕酮分泌而使血浆孕酮浓度低但不断升高的奶牛进行比较。两项实验均未发现后续发情周期中高孕酮组和低孕酮组之间血浆孕酮浓度有任何差异。在两项实验中，在孕酮处理结束18天后，后续发情周期的第15天（实验1）或第16天（实验2），两组的PGFM基础浓度相似。在两项实验中，催产素刺激后低孕酮组的PGFM浓度升高明显高于高孕酮组。这些结果表明，发情周期中孕酮浓度较低对后续周期黄体期后期子宫对催产素的反应有延迟刺激作用。由此导致的前列腺素F2α分泌增加可能会在妊娠早期干扰黄体维持。
