Neurofilament expression in bovine chromaffin cells.

Neurofilament (NF) expression was examined in adult bovine adrenal chromaffin cells by immunocytochemistry using a series of monoclonal antibodies directed against either nonphosphorylated or phosphorylated epitopes of the heavy NF subunit. In situ, this NF subunit was not detected in chromaffin cells. However, chromaffin cells grown in primary culture under standard conditions contained NF proteins, but only in a nonphosphorylated state. Phosphorylation of NFs could be induced under culture conditions favouring the development of a neuronal phenotype--40% of the cells developed neurites within a week while NF phosphorylation occurred later. Phosphorylated NFs were restricted to neurites, unlike nonphosphorylated NFs which were observed in both perikarya and neurites.