Properties as a Cation Exchanger of Chorions of Medaka Oryzias latipes and Rainbow Trout Salmo gairdneri

Abstract

Some properties as an ion exchanger of the chorions isolated from eggs of medaka Oryzias latipes and rainbow trout Salmo gairdneri were studied by using five metal ions (Ca²⁺, Cd²⁺, Mg²⁺, Mn²⁺, and Zn²⁺). The binding of these metal ions to the medaka chorion was observed in the pH region from 5 to alkaline sides. On the other hand, the binding of Ca²⁺, Mg²⁺ and Mn²⁺ to rainbow trout chorion was detected in the pH region above 6, and that of Cd²⁺ and Zn²⁺ from 5 to alkaline sides. Amounts of metal ions bound to both chorions increased with increasing pH. When both metal-binding chorions were transferred into other metal ion solutions, an ion exchange reaction between the metals bound to the chorions and the other ions in solutions took place immediately. Cd²⁺ and Zn²⁺ had a high binding affinity to both chorions, followed by Mn²⁺, Mg²⁺ and Ca²⁺. The binding affinity of Mg²⁺ was equal to that of Ca²⁺. It is thus evident that both chorions of medaka and rainbow trout eggs possess some properties of the cation exchanger which have an ion exchange group of weak acid such as -(binding site)-H⁺.