Pituitary-Adrenocortical System During Growth of a Transplantable Pituitary Tumor and After Tumor Removal

Abstract

The adrenal glands of rats bearing transplantable pituitary tumors are enlarged up to 10 times normal size due to very high blood levels of ACTH. Such enlarged adrenals have adrenal ascorbic acid levels (AAA) of 160–200 mg/100 g of adrenal weight, which is not minimal. The blood level of corticosterone (B) is only 60–70 μg/100 ml of plasma, which is not maximal. The AAA and B values are not altered by various stresses or by injection of ACTH, epinephrine, or Pitressin. The enlarged adrenals respond to ACTH in the in vitro Saffran-Schally assay with a slope one fourth that of a normal adrenal gland. The pituitary gland of the host rat atrophies to less than 50% of normal weight as the adrenal and tumor weights increase. After tumor removal the pituitary and the enlarged adrenals recover, so that there is partial responsiveness to stress in 24 hr and complete responsiveness in about 10 days, but the pituitary weight is not yet normal after 14 days. These data suggest that the prolactin and growth hormone produced along with ACTH by the tumor modify the functioning of the pituitary-adrenocortical system. (Endocrinology74: 617, 1964)