Hansel W, Stock A, Battista P J
Department of Physiology, New York State College of Veterinary Medicine, Ithaca 14853.
J Reprod Fertil Suppl. 1989;37:11-7.
Peripheral plasma progesterone concentrations are higher (P less than 0.05) in pregnant than in inseminated non-pregnant or cyclic heifers between Days 10 and 18 after insemination. In several experiments, it has been demonstrated that bovine conceptuses produce a low molecular weight (Mr less than 10,000), lipid-soluble, heat-labile, dextran-coated charcoal-adsorbable luteotrophic substance(s) that has the ability to stimulate progesterone synthesis in dispersed bovine luteal cells. This substance does not appear to be PAF, since addition of PAF to dispersed luteal cells at several dose levels failed to affect either basal or LH-stimulated progesterone synthesis. However, results of in-vitro and in-vivo experiments suggest that platelet-derived products are luteotrophic. In in-vitro experiments it was shown that co-incubation of dispersed bovine luteal cells with bovine platelets augments basal progesterone synthesis. Serotonin and platelet-derived growth factor appear to be the major products of platelet activation responsible for the luteotrophic activity of platelets. Products of the arachidonic acid cascade do not appear to be important, since addition of the cyclo-oxygenase blocker indomethacin did not reduce the luteotrophic activity of platelets. In in-vivo experiments, it has been possible to demonstrate a significant thrombocytopenia in pregnant heifers between Days 7 and 16 after insemination. These results are compatible with the concept that release of platelet-derived products under the influence of factors produced by the early embryo play a role in stimulating progesterone synthesis by the corpus luteum during early pregnancy.
在授精后第10至18天，怀孕的小母牛外周血浆孕酮浓度高于（P<0.05）已授精但未怀孕或处于发情周期的小母牛。在一些实验中，已证明牛的孕体产生一种低分子量（Mr<10,000）、脂溶性、热不稳定、可被葡聚糖包被活性炭吸附的促黄体物质，该物质能够刺激分散的牛黄体细胞中的孕酮合成。这种物质似乎不是血小板活化因子，因为在几个剂量水平下将血小板活化因子添加到分散的黄体细胞中，未能影响基础或促黄体生成素刺激的孕酮合成。然而，体外和体内实验结果表明，血小板衍生产物具有促黄体作用。体外实验表明，将分散的牛黄体细胞与牛血小板共同孵育可增强基础孕酮合成。血清素和血小板衍生生长因子似乎是血小板活化的主要产物，负责血小板的促黄体活性。花生四烯酸级联反应的产物似乎并不重要，因为添加环氧化酶阻滞剂吲哚美辛并没有降低血小板的促黄体活性。在体内实验中，已证实在授精后第7至16天怀孕的小母牛出现明显的血小板减少。这些结果与以下概念相符，即在早期胚胎产生的因子影响下，血小板衍生产物的释放对怀孕早期黄体刺激孕酮合成起作用。
