Otolith Matrix Proteins of Walleye Pollock; Biochemical Properties and Immunohistochemical Localization in the Saccular Tissue

Abstract

In teleosts, the sacculus of the inner ear contains a solid calcareous otolith, sagitta. The otolith is fixed over a region of the sensory epithelium (macula), intervened by a membrane called the otolithic membrane [1, 2]. The otolith grows in the endolymph of the saccular lumen without attachment of cells. It consists of aragonitic crystals of calcium carbonate [3], deposited on a small amount of an organic matrix consisting of proteins, glycosaminoglycans and lipids [4, 5]. The organic matrix is suggested to be produced at the macula region and diffuses into the endolymph fluid [4]. This study was performed to clarify the biochemical properties and the origin of this organic matrix. This investigation particularly focused on the calcium binding proteins extracted from walleye pollock otoliths. Biochemical properties of matrix proteins were examined by electrophoresis and ⁴⁵Ca autoradiography. The origin of these matrix proteins was studied by applying immunohistochemical techniques to the saccular epithelium.