Developmental Analysis of Calretinin Using Quantitative Analysis in Rat Cochlea / 대한이비인후과학회지

ABSTRACT

BACKGROUND AND OBJECTIVES: Calretinin is a neuron specific, high affinity cytosolic calcium-binding protein of the EF-hand family. In the mammalian inner ear, it is expressed in the organ of Corti and most of the spiral ganglion neurons. Authors observed the change of expression and amount of calretinin according to the maturation in the rat cochleae. MATERIALS AND METHOD: Sprague-Dawley rat cochleae collected from each stage (postnatal day (P) P5, P17, P35) were analyzed using 2D gel electrophoresis, proteomic analysis, Western blot analysis, and fluorescence immunocytochemistry. RESULTS: In P17 and P35, calretinin was identified at an isoelectric point (pI) of 4.9 and a molecular weight of 29 kDa in the analysis of the rat cochlea proteins using proteomic analysis. P17 and P35 revealed remarkable existence of calretinin in 2D gel electrophoresis and the Western blot, whereas P5 demonstrated no existence in 2D gel electrophoresis and weak expression in the Western blot. In fluorescence immunocytochemistry, P17 and P35 showed intense calretinin immunoreactivity in the inner hair cells and most ganglion neurons, but P5 displayed no immunoreactivity in inner hair cells and very weak expression in spiral ganglion cells. CONCLUSION: Compared with the early neonatal stage, an amount of calretinin remarkably increases during the critical period of the cochlear maturation and is maintained until the young adult stage. These results suggest that calretinin may have a specific role as a calcium-binding protein since the cochlear maturation in the rat inner ear.