Purpose: Climatic droplet keratopathy (CDK) is a humandegenerative corneal disease characterized by protein aggregation under theepithelium and caused by unfavorable environmental conditions. In an attempt todevelop an experimental animal model for CDK, we are studying the effect ofantioxidant agents in the cornea of healthy guinea pigs exposed to ultravioletradiation (UVR). Aldehyde dehydrogenase 3A1 (ALDH3A1) and 1A1 (ALDH1A1), alsoknown as crystallins, have different functions in the cornea. Among them theycontribute to corneal preservation against oxidative stress, so we decided tostudy the molecular aspects and localization of these enzymes in guinea pigcornea.

Methods: Total corneal extract as well as epithelium,stroma and endothelium extracts from male guinea pigs were used. The expressionof ALDH3A1 and ALDH1A1 was studied by means of immunoblotting, andimmunofluorescence assays. The existence of isoforms for both enzymes wasinvestigated by isoelectric focusing. The activity and specificity of ALDH3A1toward different substrates was studied by spectrophotometry and zymographyassays.

Results: ALDH3A1 and ALDH1A1 from guinea pig corneapresent some unique characteristics compared with other mammals. Both enzymeshave a molecular weight of approximately 54 kDa. Isoelectric focusing revealedtwo ALDH3A1 isozyme species of about pI 10 and one ALDH1A1 isozyme specie ofabout pI 9. ALDH3A1 and ALDH1A1were expressed in the epithelium, stroma andendothelium of the cornea. ALDH3A1 has a higher affinity for benzaldehyde thanhexanal (Km: 45.15 vs. 98.40), and the enzymatic activity was 0.0035+/-0.0026UI/mg of proteins vs. 0.0024+/-0.0072 UI/mg of proteins, respectively.

Conclusions: We have identified for the first time the presence of ALDH3A1 and ALDH1A1 enzymes in the different corneal compartments of healthy guinea pig, and also shown the tissue localization as well as the molecular characteristics of these crystallins.