Alpha-fodrin in the adrenal gland: localization by immunoelectron microscopy

Localization of fodrin, the brain equivalent of spectrin (a protein constituent of the erythrocyte membrane cytoskeleton), was investigated at the ultrastructural level in rat adrenal gland. By use of an affinity purified antibody directed against the alpha-fodrin subunit, all chromaffin cells, cortical cells, nerve fibers, and their surrounding Schwann cells were found to be labeled close to the cytoplasmic side of their plasma membranes. The labeling appeared more intense for chromaffin cells, and secretory granules and mitochondria were frequently found to be associated with the zone containing alpha-fodrin in these cells. The immunostained zone was estimated to extend 230 +/- 70 nm into the cytoplasm. This localization is discussed in terms of what is known of the properties of spectrin, and possible roles of the molecule in the chromaffin cell are suggested.