Gliemann J, Moestrup S, Henning Jensen P, Sottrup-Jensen L, Busk Andersen H, Munck Petersen C, Sonne O
Biochim Biophys Acta. 1986 Oct 1;883(3):400-6. doi: 10.1016/0304-4165(86)90276-x.
125I-labelled human pregnancy zone protein complexed with chymotrypsin was removed from the circulation with a half-time of 2.3 min after intravenous injection in rats. After 6 min about 67% of the label was present in the liver and about 3% was in the spleen, both in male and in female pregnant rats. The half-time of removal was more than 30 min for native pregnancy zone protein. Uptake into other organs, including placentae and feti, was negligible. 30 pM labelled pregnancy zone protein X chymotrypsin was specifically bound to rat hepatocytes and adipocytes and to human fibroblasts and monocyte-derived macrophages at 4 degrees C. Binding was almost completely abolished by a saturating concentration of unlabelled alpha 2-macroglobulin X trypsin. Binding of 15 pM labelled macroglobulin complex was completely abolished by a saturating concentration of pregnancy zone protein X chymotrypsin. In rat hepatocytes, binding of pregnancy zone protein complex was lower than that of alpha 2-macroglobulin complex at low ligand concentrations. Half-maximal receptor occupancy was obtained with about 300 pM pregnancy zone protein complex. Unlabelled alpha 2-macroglobulin or pregnancy zone protein complex failed to accelerate dissociation of the labelled pregnancy zone protein complex under conditions where dissociation of alpha 2-macroglobulin was markedly enhanced. It is concluded that pregnancy zone protein and alpha 2-macroglobulin complexes bind to the same receptors. The quantitative differences may be related to the fact that alpha 2-macroglobulin is a tetramer whereas the functional unit of pregnancy zone protein is probably a dimer.
静脉注射给大鼠后，125I标记的与胰凝乳蛋白酶结合的人妊娠区带蛋白从循环中清除的半衰期为2.3分钟。6分钟后，无论是雄性还是雌性妊娠大鼠，约67%的标记物存在于肝脏中，约3%存在于脾脏中。天然妊娠区带蛋白的清除半衰期超过30分钟。其在包括胎盘和胎儿在内的其他器官中的摄取量可忽略不计。30 pM标记的妊娠区带蛋白X胰凝乳蛋白酶在4℃时特异性结合大鼠肝细胞、脂肪细胞、人成纤维细胞和单核细胞衍生的巨噬细胞。未标记的α2-巨球蛋白X胰蛋白酶饱和浓度几乎完全消除了这种结合。15 pM标记的巨球蛋白复合物的结合被妊娠区带蛋白X胰凝乳蛋白酶饱和浓度完全消除。在大鼠肝细胞中，在低配体浓度下，妊娠区带蛋白复合物的结合低于α2-巨球蛋白复合物。约300 pM妊娠区带蛋白复合物可达到半数最大受体占有率。在α2-巨球蛋白解离明显增强的条件下，未标记的α2-巨球蛋白或妊娠区带蛋白复合物未能加速标记的妊娠区带蛋白复合物的解离。结论是妊娠区带蛋白和α2-巨球蛋白复合物结合到相同的受体上。定量差异可能与α2-巨球蛋白是四聚体而妊娠区带蛋白的功能单位可能是二聚体这一事实有关。
