Heterogeneity of rat neurofilament polypeptides revealed by a monoclonal antibody

A monoclonal antibody obtained from mice immunized with a crude neurofilament preparation from newborn rat brain revealed the existence of heterogeneity of the 200,000- and 150,000-dalton neurofilament polypeptides. On immunoblot the monoclonal antibody iC8 reacted with both the 200,000- and 150,000-dalton components in the CNS, but only with the 150,000-dalton polypeptide in sciatic nerve preparations. In addition, the 150,000-dalton polypeptide appeared as a single band in the sciatic nerve, whereas in the CNS a doublet was labeled by iC8. In contrast a second monoclonal antibody (3H5) reacted with the 200,000-dalton peptide and a single 150,000-dalton component in both the central and peripheral nervous system preparations. The differences revealed by iC8 were probably not due to phosphorylation, as the pattern of antibody binding in immunoblots was not changed by pretreatment with alkaline phosphatase. The findings suggest that different isoforms of neurofilament polypeptides are present in the nervous system.