Ultrastructural immunocytochemical localization of neuron-specific enolase in parafollicular cells of the rat thyroid.

Using pre- and post-embedding procedures, neuron-specific enolase and calcitonin were localized in rat thyroid parafollicular cells by light and electron microscopy. Peroxidase-antiperoxidase (PAP), biotin-avidin (ABC) and protein A--colloidal gold techniques were used. In paraffin sections neuron-specific enolase was demonstrated in all calcitonin-storing parafollicular cells in rats aging 1 to 180 days. The post-embedding procedure failed to detect neuron-specific enolase in ultrathin sections, but the enzyme could be demonstrated using a preembedding procedure. Neuron-specific enolase was localized exclusively within the cytosol of parafollicular cells, while calcitonin was localized within secretory granules applying either post- or pre-embedding incubation techniques.