Changes in rat lens calpastatin mrna during aging

Hong Ma, M. Taytor, T. Mizuno, M. Shih, Larry David, Thomas (Tom) Shearer

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Abstract

We previously reported lhat mRNA levels for the calcium-activated, cystcme protease m-calpain were 4-24 times higher in young rat lens compared to other soft tissues. Lens m-calpain mRNA also decreased with age. Purpose. The purposes of the present investigation were to: 11 Quantify mRNA levels for calpastatin, a specific inhibitor of calpains, in young ;.nd aging rat lenses. 2) Compare the levels of calpastatin mRNA in lenses to other age-matched soft tissues. Methods. Tola] RNA was isolated from lens, kidney and brain from rats ranging in age from 12 to 120 days. mRNA concentrations for calpastatin were measured by quantitative RT PCR using a competitive RNA intern; I control. Resujts. The concentration of mRNA for calpastatin in young rat lens was 1X10 copies/ ug RNA. This was at least 5 times lower than m-calpain rrRNA levels at the same age. Calpastatin mRNA in rat lens decreased approximately 10 fold during maturation. mRNA foi calpastatin in other soft tissues remained conslant (kidney) or increased (brain) over similar time period. Conclusions. These arc the first quantitative data showing that the concentration of calpastatin mRNA in young rat lens is significantly lower than the mRNA levels of m-calpain. These data suggested that the high enzymatic activity of calpain in young rat lens may he related to the highei levels of m-calpain mRNA and lower levels of calpastatin mRNA. This would allow calpain to escape the inhibitor/ action of calpastalin and increase the susceptibilitv of young ral lens to a varkty of cataracts.

Original languageEnglish (US)
JournalInvestigative Ophthalmology and Visual Science
Volume38
Issue number4
Publication statusPublished - 1997

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ASJC Scopus subject areas

  • Ophthalmology

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