ENDOCRINE FACTORS IN DEVELOPMENT OF TRANSPLANTABLE ADRENAL CORTICAL TUMORS .I. INHIBITION OF GROWTH RATE BY CORTICOTROPIN (ACTH)

The growth rate of transplantable adrenocortical tumors in male LAF 1 mice was found to be inhibited in hypophysectomized and in adrenalectomized animals. Castration and sex hormones did not affect the growth of these tumors. In intact mice a striking inhibition of the growth rate of adrenocortical tumors was brought about by the administration of ACTH. Evidence was obtained that ACTH inhibited growth by a direct action on the tumor cells. When expressed in terms of units of DNA, the biochemical and cytochemical effects on adrenocortical tumor cells appeared qualitatively similar to the effects of this hormone on the normal adrenal cortex. A single injection of ACTH stimulated the activity of glucose‐6‐phosphate dehydrogenase. Repeated administration of ACTH produced an increased oxygen uptake by sliced tissue and a moderate accumulation of RNA in the microsomal fraction. Water extracts of acetone powdered, ACTH‐treated, adrenocortical tumors had lower dCMP‐deaminase activity than extracts from untreated tumors. When expressed in terms of units of DNA, the homogenates of ACTH‐treated adrenocortical tumors had a higher succinoxidase activity and the sliced tissue had a lower rate of anaerobic glycolysis than did corresponding samples of untreated adrenocortical tumors. Copyright © 1968 Wiley‐Liss, Inc., A Wiley Company