Pituitary transplantation--a study on the response of hypophysis-adrenal axis to physiological stress

Previous studies on experimental intracerebral pituitary transplantation have shown survival and possible function of fetal pituitary glands grafted to the hypothalamic region of inbred strains. In the present study, fetal pituitary tissue was implanted into hypothalamic area of the hypophysectomized rat by stereotactic methods. We investigated the hormonal levels and secretions of fetal pituitaries grafted to the allogenic host and studied the effects of physiological stimuli on hypophysectomized rats with grafted pituitaries. We found that the fetal pituitary allografts released adrenal corticotropin (ACTH) and corticosterone in response to stimulation by corticotropin-releasing hormone (CRH), and released corticosterone alone in response to insulin-induced hypoglycemia. The grafts are acutely responsive to CRH and retain their potential for physiological regulation and function. The ACTH-releasing-signal generated in the host by insulin-induced hypoglycemia failed to activate the graft, so activation by other physiological stimuli cannot be ruled out.