晶状体上皮中钠钾ATP酶多肽上调反应

Delamere N A, Manning R E, Liu L, Moseley A E, Dean W L

Department of Ophthalmology and Visual Sciences, University of Louisville, Kentucky, USA.

Invest Ophthalmol Vis Sci. 1998 Apr;39(5):763-8.

PURPOSE

In a previous study, an increase in Na,K-ATPase alpha 2 expression was detected in the epithelium of porcine lenses exposed to amphotericin B, an ionophore that also increases lens sodium and stimulates active sodium transport. The purpose of the present study was to determine whether an increase of Na,K-ATPase alpha 2 synthesis is a response to an episode of rapid Na-K transport or whether the increase in lens sodium alone can initiate the response.

METHODS

Western blot analyses were conducted to probe for Na,K-ATPase alpha polypeptides in membrane material isolated from porcine lens epithelium. Ouabain-sensitive adenosine triphosphate hydrolysis was used as an index of Na,K-ATPase activity, and lens ion content was determined by atomic absorption spectrophotometry. 86-Rubidium (86Rb) uptake was measured as an indicator for active potassium transport.

RESULTS

86Rb uptake was markedly diminished in lenses exposed to dihydro-ouabain (DHO), signifying inhibition of active sodium-potassium transport. Consistent with this, the sodium content of DHO-treated lenses increased. By western blot analysis, a marked increase of Na,K-ATPase alpha 2 polypeptide could be detected in the epithelium of DHO-treated lenses. To rule out the possibility that apparent stimulation of Na,K-ATPase alpha 2 synthesis stemmed from binding of DHO to Na,K-ATPase sites, experiments were conducted to confirm an increase of Na,K-ATPase alpha 2 polypeptide in the epithelium of lenses exposed to low-potassium medium to inhibit active sodium-potassium transport. Consistent with the apparent increase of Na,K-ATPase polypeptide, Na,K-ATPase activity was detectably increased in epithelial material isolated from lenses pretreated with DHO or low-potassium medium.

CONCLUSIONS

An increase in Na,K-ATPase alpha 2 polypeptide can occur in the epithelium of lenses subjected to an episode of sodium pump inhibition. This suggests the response could be triggered by an increase in cell sodium and does not necessarily require a period of stimulated active sodium-potassium transport.

目的

在先前的一项研究中，在暴露于两性霉素B的猪晶状体上皮中检测到钠钾ATP酶α2表达增加，两性霉素B是一种离子载体，它也会增加晶状体钠含量并刺激钠的主动转运。本研究的目的是确定钠钾ATP酶α2合成的增加是对快速钠钾转运事件的反应，还是仅晶状体钠含量的增加就能引发该反应。

方法

进行蛋白质印迹分析以探测从猪晶状体上皮分离的膜材料中的钠钾ATP酶α多肽。哇巴因敏感的三磷酸腺苷水解用作钠钾ATP酶活性的指标，晶状体离子含量通过原子吸收分光光度法测定。测量86铷（86Rb）摄取作为主动钾转运的指标。

结果

暴露于二氢哇巴因（DHO）的晶状体中86Rb摄取明显减少，这表明主动钠钾转运受到抑制。与此一致的是，DHO处理的晶状体钠含量增加。通过蛋白质印迹分析，在DHO处理的晶状体上皮中可检测到钠钾ATP酶α2多肽明显增加。为了排除DHO与钠钾ATP酶位点结合导致钠钾ATP酶α2合成明显刺激的可能性，进行实验以确认暴露于低钾培养基以抑制主动钠钾转运的晶状体上皮中钠钾ATP酶α2多肽增加。与钠钾ATP酶多肽的明显增加一致，在用DHO或低钾培养基预处理的晶状体分离的上皮材料中，钠钾ATP酶活性可检测到增加。