Scott J, Maze M, Peters T J
Biochim Biophys Acta. 1982 Dec 17;719(3):464-73. doi: 10.1016/0304-4165(82)90234-3.
In adult male rats, fed prednisolone (0.75 mg/kg/day) for 7 days, brush border aminopeptidase activity was increased (P less than 0.001) by 106% compared to pair-fed controls. [14C]Tyrosine was injected intraperitoneally 16 h and [3H]tyrosine 6 h before death. The 3H/14C ratio was 1.79 +/- 0.21 (S.D.) in purified microvillus membranes from treated rats compared to 1.30 +/- 0.16 (P less than 0.01) in controls. Polyacrylamide gel electrophoresis of brush border membranes under denaturing conditions showed that the increased double-isotope ratio in membranes from treated rats was mainly in the high molecular weight protein subunits (greater than 80 kDa). Detergent-solubilized aminopeptidase was purified after in vivo labeling by protein A-Sepharose-antiaminopeptidase affinity chromatography. The 3H/14C ratio in aminopeptidase was 2.42 +/- 0.15 (P less than 0.05) in treated rats compared to 1.63 +/- 0.13 in controls. Over the experimental period steady-state isotope reutilization and protein labeling was demonstrated and there was no isotope metabolism. Total microvillus membrane lipid content was unaffected by prednisolone. We conclude that prednisolone increases brush border aminopeptidase activity by increasing enzyme turnover. Other high molecular weight brush border proteins were similarly affected.
在成年雄性大鼠中，给予泼尼松龙（0.75毫克/千克/天）7天，与配对喂食的对照组相比，刷状缘氨肽酶活性增加（P<0.001），增幅为106%。在处死前16小时腹腔注射[14C]酪氨酸，6小时前注射[3H]酪氨酸。与对照组的1.30±0.16（P<0.01）相比，处理组大鼠纯化微绒毛膜中的3H/14C比值为1.79±0.21（标准差）。在变性条件下对刷状缘膜进行聚丙烯酰胺凝胶电泳显示，处理组大鼠膜中增加的双同位素比值主要存在于高分子量蛋白质亚基（大于80 kDa）中。通过蛋白A-琼脂糖-抗氨肽酶亲和色谱对体内标记后的去污剂溶解的氨肽酶进行纯化。与对照组的1.63±0.13相比，处理组大鼠氨肽酶中的3H/14C比值为2.42±0.15（P<0.05）。在实验期间，证明了稳态同位素再利用和蛋白质标记，且不存在同位素代谢。泼尼松龙对微绒毛膜总脂质含量无影响。我们得出结论，泼尼松龙通过增加酶周转率来提高刷状缘氨肽酶活性。其他高分子量刷状缘蛋白也受到类似影响。
