Orwig K E, Bertrand J E, Ou B R, Forsberg N E, Stormshak F
Department of Biochemistry and Biophysics, Oregon State University, Corvallis 97331-6702.
Endocrinology. 1994 Jan;134(1):78-83. doi: 10.1210/endo.134.1.8275972.
An experiment was conducted to determine whether prostaglandin F2 alpha (PGF2 alpha)-induced secretion of oxytocin (OT) by the bovine corpus luteum (CL) was associated with changes in the activities of protein kinase-C (PKC), calpains, and calpastatin. On day 8 of the estrous cycle (estrus = day 0), beef heifers were restrained and given a 500-micrograms iv injection of cloprostenol, a PGF2 alpha analog. Corpora lutea were surgically removed from beef heifers 0, 2, 7.5, or 30 min (n = 4 animals/time period) after cloprostenol injection. Blood samples were collected before injection and at frequent intervals after injection. Distribution of PKC activity in cytosol and membrane fractions and activities of microcalpain, millicalpain, and calpastatin were determined for all CL. OT was measured in plasma and tissue by RIA. Relative to mean plasma levels of OT at time zero (85 +/- 7 pg/ml), peak plasma levels occurred between 1.5-10 min (270 +/- 36 pg/ml) for all animals. The mean luteal concentration of OT was greater at 0, 2, and 7.5 min (145 +/- 27, 232 +/- 82 and 269 +/- 115 ng/g, respectively) than at 30 min (93 +/- 33), but differences in tissue OT over time were not significant (P > 0.05). PKC activities (percentage over nonactivated control values) in the membrane or cytosolic fractions did not differ significantly among the times of CL removal; however, membrane PKC activity was positively correlated with the plasma OT level at the time of CL removal (r = 0.82; P < 0.0025). Luteal millicalpain activity was approximately twice that of microcalpain at each time point (P < 0.001), although the activities of the individual calpains over time after PGF2 alpha injection did not change. Calpastatin activity was significantly higher at 30 min (515 +/- 28 U/g tissue) than at 0, 2, or 7.5 min (373 +/- 26, 423 +/- 26, and 426 +/- 24 U/g tissue, respectively). PKC activity in the membrane appears to be positively correlated with OT secretion from the bovine CL, and increased calpastatin activity after PGF2 alpha injection may inhibit calpains present in the CL, thereby maintaining an active pool of PKC.
进行了一项实验，以确定前列腺素F2α（PGF2α）诱导牛黄体（CL）分泌催产素（OT）是否与蛋白激酶C（PKC）、钙蛋白酶和钙蛋白酶抑制蛋白活性的变化有关。在发情周期的第8天（发情期=第0天），对肉用小母牛进行保定，并静脉注射500微克氯前列醇（一种PGF2α类似物）。在注射氯前列醇后0、2、7.5或30分钟（每个时间段n = 4头动物），从肉用小母牛身上手术摘除黄体。在注射前和注射后频繁采集血样。测定所有黄体中PKC活性在胞质和膜组分中的分布以及微钙蛋白酶、毫钙蛋白酶和钙蛋白酶抑制蛋白的活性。通过放射免疫分析法测定血浆和组织中的OT。相对于零时的平均血浆OT水平（85±7皮克/毫升），所有动物的血浆OT峰值水平出现在1.5 - 10分钟之间（270±36皮克/毫升）。在0、2和7.5分钟时，黄体中OT的平均浓度（分别为145±27、232±82和269±115纳克/克）高于30分钟时（93±33），但组织中OT随时间的差异不显著（P>0.05）。在摘除黄体的不同时间，膜或胞质组分中的PKC活性（相对于未激活对照值的百分比）没有显著差异；然而，膜PKC活性与摘除黄体时的血浆OT水平呈正相关（r = 0.82；P<0.0025）。在每个时间点，黄体中的毫钙蛋白酶活性约为微钙蛋白酶活性的两倍（P<小于0.001），尽管在PGF2α注射后，各个钙蛋白酶的活性随时间没有变化。钙蛋白酶抑制蛋白活性在30分钟时（515±28单位/克组织）显著高于0、2或7.5分钟时（分别为373±26、423±26和426±24单位/克组织）。膜中的PKC活性似乎与牛黄体分泌OT呈正相关，并且在PGF2α注射后钙蛋白酶抑制蛋白活性增加可能会抑制黄体中存在的钙蛋白酶，从而维持PKC的活性池。
