Quinacrine accumulates in certain peptide hormone-producing cells.

Quinacrine is a fluorescent anti-malarial acridine derivative which binds selectively to a population of nerves, presumably peptidergic, and to certain peptide hormone-producing cells. Among these cells are glycopeptide hormone-producing cells in the adenohypophysis, the calcitonin cells in the thyroid, the insulin, glucagon and PP cells in the pancreatic islets, and the gastrin cells in the pyloric antrum. Available evidence suggests that the fluorophore accumulates in the secretory granules. The half-life of the fluorescence varies from one cell type to another, from 6 h in the gastrin cells to 40 h in the insulin cells. It cannot be excluded that the half-life of the fluorescence reflects the turn-over rate of the secretory granules and that the disappearance rate of the fluorescence is dependent upon the secretory activity of the cell.