Cardiomyopathy (CM) is degenerative disease of myocardium which leads to severe cardiac failure. Although many causative genes for CM have been identified, molecular pathogenesis of CM is not fully understood. In this study, we searched for a novel pathway recruited in the development of CM by using BIO14.6 hamster as an animal model for human CM. We screened upregulated genes in the left ventricle by differential display technique and searched for a gene which had never been linked to CM. We identified a novel gene overexpressed in BIO14.6 hamster ventricles, which was considered to be a new member of aldo-keto reductase (AKR) superfamily. The cloned cDNA encoded a 316 amino acid polypeptide with calculated molecular mass of 35,804, which showed high amino acid sequence similarities to aldose reductase and its relative: 69.6% to AKR1B1 (human aldose reductase), 68.4% to AKR1B3 (mouse aldose reductase), and 85.8% to AKR1B7 (mouse vas deferens protein). The upregulation of this aldose reductase-like gene in BIO14.6 hamster ventricles (6.3 ± 0.8-fold) seemed to be influenced by the overexpression of activator protein-1 present there. With the fact that AKR1B1, AKR1B3, and AKR1B7 have synthetic activities of prostaglandin F2α, the aldose reductase-like protein could cause cardiac hypertrophy through production of prostaglandin F2α whose precursor and receptor were abundant in BIO14.6 hamster ventricles. Aldose reductase and its related proteins would give a new clue to dissect the pathogenesis of CM including oxidative stress and cardiac hypertrophy, and to develop a new drug for the treatment of CM.