Tetrodotoxin-sensitive protein in the extracts from excitable tissues.

The sodium permeability of liposomes preincubated with the soluble fraction of brain and heart muscle homogenates was increased veratrine. The veratrine increment was decreased by tetrodotoxin. The effect was specific for the extracts from excitable tissues. Bovine serum and soluble fraction of liver homogenate induced neither veratrine- nor tetrodotoxin-sensitivity of the liposomes. Treatment of the excitable tissue extracts by pronase and heat denaturation caused their complete inactivation. Tetrodotoxin-sensitive factor could be fractionated by ammonium sulfate precipitation and by DEAE-Servacel chromatography. On a column of Sephadex G-200 it was eluted with the void volume. It is suggested that the tetrodotoxin-sensitive factor is a protein which could be a soluble precursor of the voltage-dependent sodium channels.