Gross T S, Thatcher W W, Hansen P J, Johnson J W, Helmer S D
Department of Dairy Science, University of Florida, Gainesville 32611.
Prostaglandins. 1988 Mar;35(3):359-78. doi: 10.1016/0090-6980(88)90128-1.
Previous studies have detected reduced endometrial secretion of prostaglandins during pregnancy in cattle. The present experiment tested the hypothesis that reduced secretion of prostaglandins is caused by induction of an intracellular endometrial inhibitor of prostaglandin synthesis. The microsomal fraction of parturient bovine cotyledons was utilized as a source of enzymes for prostaglandin synthesis. Endometrial tissues collected at Day 17 of the estrous cycle (n = 12) and pregnancy (n = 12) were homogenized and subjected to differential centrifugation for preparation of microsomes and a high-speed (100,000 x g) cytosolic supernatant. Endometrial intracellular preparations were then examined for the ability to modulate prostaglandin synthesis by cotyledonary microsomes from parturient cows. Endometrial intracellular preparations from cyclic cows decreased (P less than 0.05) PGF synthesis by cotyledonary microsomes to a slight extent (supernatant, 21% reduction; microsomes, 11% reduction), while preparations from pregnant cows markedly decreased (P less than 0.01) PGF synthesis (supernatant, 63% reduction; microsomes, 28% reduction; supernatants vs microsomes, P less than 0.01). Regardless of the amount of arachidonic acid available as substrate (25-400 micrograms) endometrial supernatant from pregnant cows (pooled sample) caused a 50% inhibition (IC50) of prostaglandin synthesis at a tissue equivalent of 270 +/- 9.1 mg. The mechanism of inhibition by endometrial high-speed supernatant from pregnant cows appears to be non-competitive with respect to arachidonic acid. The inhibitor(s) may be proteinaceous (70-75 kDa and 25-35 kDa) and can be precipitated by 20% saturated ammonium sulfate. In conclusion, early pregnancy in cattle appears to be associated with increased amounts of an intracellular endometrial inhibitor of prostaglandin synthesis.
以往研究已检测到牛在怀孕期间子宫内膜前列腺素分泌减少。本实验检验了以下假说：前列腺素分泌减少是由诱导子宫内膜细胞内前列腺素合成抑制剂所致。分娩期牛胎盘小叶的微粒体部分被用作前列腺素合成酶的来源。收集发情周期第17天（n = 12）和怀孕期（n = 12）的子宫内膜组织，进行匀浆并经差速离心制备微粒体和高速（100,000×g）胞质上清液。然后检测子宫内膜细胞内制剂对分娩期母牛胎盘小叶微粒体前列腺素合成的调节能力。发情周期母牛的子宫内膜细胞内制剂使胎盘小叶微粒体的PGF合成略有减少（P < 0.05）（上清液减少21%；微粒体减少11%），而怀孕母牛的制剂则显著减少（P < 0.01）PGF合成（上清液减少63%；微粒体减少28%；上清液与微粒体相比，P < 0.01）。无论作为底物的花生四烯酸量如何（25 - 400微克），怀孕母牛的子宫内膜上清液（混合样本）在组织当量为270±9.1毫克时可导致前列腺素合成50%的抑制（IC50）。怀孕母牛子宫内膜高速上清液的抑制机制似乎对花生四烯酸是非竞争性的。该抑制剂可能是蛋白质类（70 - 75 kDa和25 - 35 kDa），可被20%饱和硫酸铵沉淀。总之，牛的早期妊娠似乎与子宫内膜细胞内前列腺素合成抑制剂的量增加有关。
