PARTIAL-PURIFICATION AND CHARACTERIZATION OF NEUROTROPHIC SUBSTANCE AFFECTING TETRODOTOXIN SENSITIVITY OF ORGAN-CULTURED MOUSE MUSCLE

From mouse spinal cord homogenate, we isolated a trophic substance which reverses the post-denervation decrease in tetrodotoxin sensitivity of action potential in organ-cultured extensor digitorum longus muscle of mouse and characterized its physicochemical properties. The trophic substance was separated from macromolecules in homogenate by gel filtration on Biogel P2 column. The partially purified trophic substance was heat-stable, acid-stable and alkaline-labile. The trophic activity was destroyed by lyophilization at neutral pH but not at acidic pH. The trophic activity was abolished by incubation with pronase or leucine aminopeptidase, but not by trypsin, chymotrypsin, thermolysin or carboxypeptidase A. The trophic substance passed through an ultrafiltration membrane UM10 freely. A small part of the trophic activity passed through a UM2 or UM05, and the rest was retained on the membranes. The trophic substance adsorbed on CM-Sephadex at pH 7.2 but passed through DEAE-Sephadex at pH 8.4. These results suggest that the trophic substance regulating tetrodotoxin sensitivity of action potential in mouse skeletal muscle is a peptide with a rather low molecular weight of less than 10,000 and that while the N-terminus of the peptide is free, the C-terminus is probably blocked. This peptide differs from other trophic substances reported previously by other investigators. © 1979.