Norling L L, Colca J R, Brooks C L, Kloepper R F, McDaniel M L, Landt M
Biochim Biophys Acta. 1984 Sep 28;801(2):197-205. doi: 10.1016/0304-4165(84)90068-0.
Studies were undertaken to determine whether the effect of alloxan to inactivate a membrane-bound calcium- and calmodulin-dependent protein kinase was specific for the pancreatic islets and whether inactivation of the kinase occurred also after injection of a diabetogenic dose of alloxan into rats. The effect of alloxan was also examined on similar particulate calcium- and calmodulin-dependent kinases present in two other secretory tissues, mammary acini and forebrain. Exposure of alloxan to cell-free preparations of all secretory tissues examined inhibited the calcium- and calmodulin-dependent kinase activities, suggesting that the specificity of alloxan action was not due to the presence in islets of a kinase uniquely sensitive to alloxan. To determine whether the selective effect of alloxan action was mediated at the cellular level, experiments were performed with alloxan presented to intact cells. Whereas alloxan exposure to viable cell preparations of islets and brain decreased the subsequently measured calcium- and calmodulin-dependent protein kinase activity, the activity measured in mammary acini exposed to these alloxan concentrations was unaffected. Injection (i.v.) of a diabetogenic dose of alloxan (50 mg/kg) produced an immediate (10 min) and selective inactivation of the calcium- and calmodulin-dependent protein kinase in pancreatic islets but had no effect on the similar kinases measured in brain and mammary acini. These results indicate that the unique sensitivity of islets to alloxan may result from the ability of alloxan to rapidly gain intracellular access and then inactivate this kinase activity. The selective effect of alloxan injection on this islet protein kinase is consistent with the hypothesis that inactivation of the kinase by alloxan is related to its diabetogenic effect in vivo.
开展了多项研究，以确定四氧嘧啶使膜结合钙和钙调蛋白依赖性蛋白激酶失活的作用是否对胰岛具有特异性，以及在给大鼠注射致糖尿病剂量的四氧嘧啶后，该激酶是否也会失活。还研究了四氧嘧啶对另外两个分泌组织（乳腺腺泡和前脑）中存在的类似颗粒性钙和钙调蛋白依赖性激酶的影响。将四氧嘧啶与所有检测的分泌组织的无细胞制剂一起孵育，可抑制钙和钙调蛋白依赖性激酶活性，这表明四氧嘧啶作用的特异性并非由于胰岛中存在对四氧嘧啶独特敏感的激酶。为了确定四氧嘧啶作用的选择性效应是否在细胞水平介导，对完整细胞进行了四氧嘧啶实验。虽然将四氧嘧啶与胰岛和脑的活细胞制剂一起孵育会降低随后测得的钙和钙调蛋白依赖性蛋白激酶活性，但暴露于这些四氧嘧啶浓度下的乳腺腺泡中测得的活性未受影响。静脉注射致糖尿病剂量的四氧嘧啶（50mg/kg）会使胰岛中的钙和钙调蛋白依赖性蛋白激酶立即（10分钟）选择性失活，但对脑和乳腺腺泡中测得的类似激酶没有影响。这些结果表明，胰岛对四氧嘧啶的独特敏感性可能源于四氧嘧啶迅速进入细胞内并使该激酶活性失活的能力。四氧嘧啶注射对这种胰岛蛋白激酶的选择性作用与四氧嘧啶使该激酶失活与其在体内的致糖尿病作用相关的假设一致。
