Purpose: To measure concentrations of mRNA for calpain II in normal, aging and cataractous rat lens and compare them to other tissues and human lens. Methods: Quantitative RT-PCR for calpain II mRNA was performed using competing, deletion-mutant mRNA. Calpain II mRNA was quantitated in lens and other tissues from aging rats, in lenses undergoing formation of selenite cataract, and in human donor lenses. Results: mRNA for calpain II was highest in the outer regions of young rat lens at 5x106 copies/μg total RNA- at least five times higher than young human lens. Unlike the lower and constant levels in rat liver, kidney, and lung; calpain mRNA in rat lens decreased with age. Early-stage selenite cataract showed a two fold increase in calpain mRNA, while later stage nuclear cataract showed a 64% loss. Significance: These are the first quantitative data showing that the concentration of calpain II mRNA in young rat lens is significantly higher than other tissues and can change rapidly during aging and cataract formation. These data help explain high enzymatic activity of calpain II in young rat lens, susceptibility of young rat lens to a variety of cataracts showing increased calcium and calpain-induced proteolysis, loss of susceptibility to experimental cataract with age, and low calpain enzyme activity in human lens. Regulators of calpain activity include changes in calcium, the presence of endogenous inhibitor calpastatin, and binding to membranes or substrates. The level of calpain II mRNA is now shown to be an additional regulator of calpain II proteolytic activity in rat lens.
|Original language||English (US)|
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - Feb 15 1996|
ASJC Scopus subject areas
- Sensory Systems
- Cellular and Molecular Neuroscience