Lack of detectable secretion of ACTH from pituitary homografts of pars intermedia

Hypophysectomized rats bearing grafts of the pars intermedia (PI) in the kidney capsule for 20 days did not show adrenal weights significantly different from those of hypophysectomized controls. Plasma corticosterone was undetectable in the grafted rats, even after the injection of lysine-vasopressin or histamine. On the other hand, MSH activity was present in measueable amounts, independent of the drug administered, in the plasma of the grafted rats. These results suggest that PI transplants do not have the ability to release ACTH, even though it has been previously reported that they contain this hormone.