Functional Restitution of Pituitary Grafts Re-Transplanted From Kidney to Median Eminence¹

The present study is based on the fact that rat pituitaries autografted on the kidney lose power to maintain ovarian follicles and interstitium, although luteotropic function is retained or enhanced. In 62 adult, cycling rats the pars distalis was autotransplanted to the kidney immediately after parapharyngeal hypophysectomy In the definitive experimental group of 14 rats (MEm-1) the grafts were re-transplanted after 3 to 4 weeks via the transtemporal route into close relation to the median eminence. Estrous cyclesreturned spontaneously in 13 animals 8 to 68 days later; 7 rats became pregnant. Ovaries, uteri and vaginae were histologically normal save for reduced numbers of follicles and corpora lutea. In another group of 10 rats (MEm-2) grafts were re-transplanted under the median eminence 2 to 3 weeks after the first operation. These were each “primed” later with a short sequence of FSH and LH injections, a treatment of little benefit. Gonadotropin secretion became evident at 11 to 66 days; 3 rats cycled while 4 became persistent-estrous; none was fertile. In 21 control animals (group TL) in which the graft was re-transplanted from kidney to a site under the temporal lobe and in 17 rats (group Ky) in which the grafts remained on the kidney, there was no sign of return of FSH and/or LH secretion during experimental periods of 30 to 105 days. Adrenals and thyroids were studied histologically, ACTH was evaluated functionally by adrenal hypertrophy after unilateral adrenalectomy, and TSH was evaluated by thyroid uptake of I131. While residual stimulation of adrenals and thyroids was evident in control groups TL and Ky, there was significant improvement in group MEm-1. Group MEm-2 was not studied. In the MEm group all grafts were closely adherent to the median eminence. Results clearly demonstrate that the extreme functional deficiencies observed when the pars distalis is removed to sites distant from the hypothalamus are caused by the loss of hypothalmic influences, stimuli that are probably mediated by the hypophysial portal vessels. This is true with respect to secretion of ACTH, TSH, FSH and LH.