Correlation of alkaline phosphatase staining of cortisol-producing adrenocortical tumors with dexamethasone suppression and ACTH stimulation.

The histochemical activity of alkaline phosphatase (Al-Pase), the induction of which is one of the effects of ACTH on the adrenocortical cells, was examined in 10 adrenocortical tumors causing Cushing's syndrome and in 65 adrenal cortices. All of the compact cells in every gland, and almost all, about half, or a small proportion in the four tumors showed Al-Pase activity. These tumors decreased in steroidogenesis after the administration of dexamethasone. No compact cells exhibited the activity in six tumors, none of which was "dexamethasone-suppressible". Three of the seven attached glands examined were halfway between those of typical Cushing's syndrome and those of other than Cushing's syndrome from the viewpoint of compact/clear cell morphology. All of the tumors that had Al-Pase-positive clear cells increased in steroidogenesis after ACTH administration. These results suggested that Al-Pase activity of tumor cells was also ACTH effect and that a decrease in steroidogenesis of tumors after dexamethasone administration was due not to fluctuations but to suppression of intrinsic ACTH.