Nabekura T, Takeda M, Hori R, Tomohiro M, Ito Y
School of Pharmaceutical Sciences, Kinki University, Kowakae, Higishi-Osaka 577-8502, Japan.
Curr Eye Res. 2001 Jun;22(6):446-50. doi: 10.1076/ceyr.22.6.446.5488.
The regulation of calcium concentration in lens cells is important in the mechanisms of cataractogenesis. The Ca( 2+) level in cells is controlled by plasma membrane Ca(2+)-ATPase (PMCA). PMCA has several isoforms that are distributed in various cell types in the body. In this study, we investigated the PMCA mRNA expression in normal lenses and in lenses from rats with newly developed hereditary cataracts.
The rats used were the UPL strain of Sprague-Dawley rats, with (UPL) and without (normal) the dominant gene for cataracts. PMCA mRNA expression in the lens, brain, liver and kidney in the normal and UPL rats was detected by reverse transcription-PCR using isoform specific primers. Partial cDNA sequences of the lens PMCA were also determined.
PMCA1, 2, 3 and 4 were expressed in the brain and kidney. Distinct from the brain, liver and kidney, only one isoform of PMCA, PMCA1b, was expressed in both normal and UPL rat lenses. Sequences of PMCA in normal and UPL rat lenses were not different.
The present study demonstrated that PMCA1b is the only form of PMCA present in both normal and UPL rat lenses.
晶状体细胞中钙浓度的调节在白内障形成机制中很重要。细胞内的Ca(2+)水平由质膜Ca(2+)-ATP酶（PMCA）控制。PMCA有几种同工型，分布于体内各种细胞类型中。在本研究中，我们调查了正常晶状体以及新发生遗传性白内障的大鼠晶状体中PMCA mRNA的表达情况。
所用大鼠为斯普拉格-道利大鼠的UPL品系，有（UPL）和无（正常）白内障显性基因。使用同工型特异性引物，通过逆转录-PCR检测正常大鼠和UPL大鼠晶状体、脑、肝和肾中PMCA mRNA的表达。还测定了晶状体PMCA的部分cDNA序列。
PMCA1、2、3和4在脑和肾中表达。与脑、肝和肾不同，正常和UPL大鼠晶状体中仅表达一种PMCA同工型，即PMCA1b。正常和UPL大鼠晶状体中PMCA的序列没有差异。
本研究表明，PMCA1b是正常和UPL大鼠晶状体中存在的唯一PMCA形式。
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