Expression of plasma membrane Ca(2+)-ATPase in lenses from normal and hereditary cataract UPL rats.

PURPOSE: 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.

METHODS: 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.

RESULTS: 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.

CONCLUSIONS: The present study demonstrated that PMCA1b is the only form of PMCA present in both normal and UPL rat lenses.