Abstract
Extracts of fetal calf brain cause a 3- to 5-fold increase in acetylcholine receptors (AcChoR) on cultured myogenic L5 cells. Purification of the substance causing the major portion of this receptor increase was completed. UV spectral characteristics, NMR, mass spectra and AcChoR induction by the active factor are the same as those of commercially available ascorbic acid. The biological activity of ascorbic acid is not mimicked by reducing agents with or without sulfhydryl groups. Compounds related to ascorbic acid were tested for their ability to induce AcChoR increases on L5 cells. D-Isoascorbic acid is the only substance with identical biological activity to ascorbic acid. Dehydroascorbic acid and ascorbic acid 2-O-sulfate also induce AcChoR increases but with lower specific activity. Ascorbic acid can play a role in regulating AcChoR expression in myogenic tissue, and the presence of ascorbic acid in the purified fraction from fetal calf brain accounts for its ability to increase AcChoR in L5 cells.