Involvement of calpain isoforms in retinal degeneration in WBN/Kob rats

Mitsuyoshi Azuma, Kanako Sakamoto-Mizutani, Takeshi Nakajima, Sayaka Kanaami-Daibo, Yoshiyuki Tamada, Thomas R. Shearer

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


Results of our recent studies in rats suggested that calpains play an important role in retinal cell death induced by ischemia-reperfusion in vivo and by hypoxia in vitro. Study of spontaneous animal models could help determine the involvement of calpains in human retinopathy. The WBN/Kob rat is such a model for spontaneous retinal degeneration. The purpose of the study reported here was to determine the involvement of calpain isoforms during retinal degeneration in WBN/Kob rats. Histologic and functional retinal degeneration in WBN/Kob rats was observed by use of light microscopy and electroretinography, respectively. Proteolysis of α-spectrin in the retina was detected by use of immunoblot analysis in aging WBN/Kob rats. This proteolysis was associated with the increases of retinal calcium content and caseinolytic activity for calpains 1 and 2. Expression of calpain 1, calpain 2, and calpastatin mRNAs in the retina, as measured by use of reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, were only slightly up-regulated at 24 weeks of age. In contrast, expression of retina-specific calpains, such as Rt88, Rt88', and Rt90 mRNA, was markedly down-regulated at 12 weeks of age. Expression of calpain 10 mRNA in the retina was only slightly down-regulated at 12 weeks of age. In contrast to mRNA expression, various expression patterns of calpain 10 proteins were observed. Increased retinal calcium content, leading to activation of calpains 1 and 2, may be an important event in the sequential changes leading to degeneration of the retina in WBN/Kob rats. Activated calpain causing proteolysis of α-spectrin and changes in Rt88, Rt88', Rt90 and calpain 10 may also contribute to retinal degeneration.

Original languageEnglish (US)
Pages (from-to)533-542
Number of pages10
JournalComparative Medicine
Issue number5
StatePublished - Oct 2004
Externally publishedYes

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology
  • General Veterinary


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