Differences in glycoconjugates of adrenocorticotropic hormone-secretory granules between nonadenomatous pituitary cells and adenoma cells as detected by double labeling.

Lectin binding sites of adrenocorticotropic hormone (ACTH) secretory granules of human pituitary adenomas and of nonadenomatous pituitary tissue adjacent to adenomas were studied by postembedding immunocytochemical doublestaining on ultrathin sections followed by electron microscopy. The specific hormones produced by the secretory granules were identified by labeling one side of the section with anti-human pituitary hormone antibodies conjugated to gold particles. Simultaneously, the other side was labeled with horseradish peroxidase-lectin to reveal lectin binding sites. Specimens were obtained from four human ACTH-producing pituitary adenomas and from nonadenomatous pituitary tissue surrounding three other adenomas. The four ACTH-producing adenomas showed either weak or negative reactions with concanavalin A, whereas the nonadenomatous ACTH-producing pituitary cells reacted strongly with concanavalin A. Moreover, ACTH secretory granules were significantly larger in the nonadenomatous cells than in adenoma cells. Differences in biochemical structure and ultrastructure between nonadenomatous (normal) pituitary cells and adenoma cells secreting the same specific hormones were demonstrated, and the clinical implications of the results were discussed.