Tissues from 12 human corticotropin-secreting adenomas, obtained during transsphenoidal surgery for Cushing's disease (CD, ten cases) or Nelson's syndrome (NS, two cases), were mechanically dispersed. The resulting single cells and cell aggregates were plated on extracellular matrix derived from bovine corneal endothelia. CD and NS cells showed distinct morphological differences initially, CD cells being much more spherical than the flattened NS cells. By 10 days at the latest after plating, however, CD and NS cells were indistinguishable morphologically. Cultured cells from both entities responded with rounding to cortisol (hydrocortisone, 10(-6) M) within 4-6 h. Synthetic ovine corticotropin-releasing factor (10(-8) M) produced flattening and extension of cytoplasmic processes after as early as 2 h.