THE RECEPTIVE MECHANISM OF VARIOUS METALLIC IONS IN THE LATERAL-LINE ORGAN OF THE TADPOLES OF RANA CATESBEIANA

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Abstract
The stimulating effct on the receptor organ of various monoand divalent metallic ions on the lateral-line nerve of tadpoles was studied. The orders of the effectiveness were Ag+>Tl+>K+=Na+>Li for monovalent ions and Sr2+>Mg2+≥Ba2+>Cd2+≥Co2+>Mn2+>Zn2+ for divalent ions.Both agree well with the order of Pearson's softness parameter for monovalent ions and Edwards'modified parameter for divalent ones. All sorts of divalent cations exhibited suppressive effects on the stimulating effect of the monovalent cations when they were applied together with the monovalent cations. A simple selection rule was found for the suppressive effect. The stimulating effect of Na+ or K+ was suppressed by all sorts of divalent cations. But the effect of Ag+ was suppressed by Cd2+, but not by Mg2+ nor by Ca2+. In order to remove the Ag+effect, a dilute solution of DTT was used, although the effect of K+ or Na+ was removed easily by rinsing with distilled water. From these results the receptive mechanism of the endorgan was thought to be chemical adsorption of ions in the receptor cell membrane. Based on the principle of “hard and soft acid and base”, it is suggested that there are two types of binding sites for the ions on the membrane, a soft site and a hard one.

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