Mito T, Kuwahara S, Delamere N A
Department of Ophthalmology and Visual Sciences, Kentucky Lions Eye Research Institute, University of Louisville School of Medicine 40292, USA.
Curr Eye Res. 1995 Aug;14(8):651-7. doi: 10.3109/02713689508998492.
Experiments were conducted to test the influence of thapsigargin on the NaK-ATPase activity of cultured cells (ODM2) derived from human nonpigmented ciliary epithelium. The rate of ouabain-sensitive ATP hydrolysis (Na,K-ATPase activity) was diminished in cells that had been pretreated with thapsigargin then permeabilized. Following 20 min exposure of intact cells to thapsigargin, the cells were permeabilized with digitonin and the rate of ouabain-sensitive ATP hydrolysis (Na,K-ATPase activity) was measured immediately in a calcium-free buffer. In permeabilized cells that had been pretreated with 1 microM thapsigargin for 20 min, the rate of ouabain-sensitive ATP hydrolysis (Na,K-ATPase activity) was reduced by 38%. Pretreatment with lesser concentrations of thapsigargin caused smaller changes of Na,K-ATPase activity. The decrease of Na,K-ATPase activity was the same whether or not calmodulin antagonists W7 or trifluoperazine were present during the thapsigargin pretreatment period. This inhibitory effect upon the Na,K-ATPase may serve to limit the extent of sodium pump activation that takes place in intact cells when thapsigargin causes sodium pump stimulation by a mechanism that appears to involve changes in cytoplasmic ion levels when potassium channels open.
开展实验以测试毒胡萝卜素对源自人非色素睫状上皮的培养细胞（ODM2）的钠钾ATP酶活性的影响。在用毒胡萝卜素预处理然后透化的细胞中，哇巴因敏感的ATP水解速率（钠钾ATP酶活性）降低。完整细胞暴露于毒胡萝卜素20分钟后，用洋地黄皂苷使细胞透化，并立即在无钙缓冲液中测量哇巴因敏感的ATP水解速率（钠钾ATP酶活性）。在用1微摩尔毒胡萝卜素预处理20分钟的透化细胞中，哇巴因敏感的ATP水解速率（钠钾ATP酶活性）降低了38%。用较低浓度的毒胡萝卜素预处理引起钠钾ATP酶活性的较小变化。无论在毒胡萝卜素预处理期间是否存在钙调蛋白拮抗剂W7或三氟拉嗪，钠钾ATP酶活性的降低都是相同的。这种对钠钾ATP酶的抑制作用可能有助于限制当毒胡萝卜素通过一种似乎涉及钾通道开放时细胞质离子水平变化的机制引起钠泵刺激时，完整细胞中发生的钠泵激活程度。
