Gonadotropic activity of neonatal pituitary glands implanted in the rat brain

¹ Department of Anatomy, University of Cincinnati, School of Medicine, Cincinnati, Ohio

Pituitary glands of neonatal rats were implanted by stereotaxic methods in various hypothalamic areas of the brains of adult, hypophysectomized male rats. Of 58 implantations, 44 viable grafts composed of pars distalis, intermedia, and epithelioid-like nervosa were found 3 months later. In none of the graft-bearing animals was there any evidence of thyrotropic or corticotropic activity as judged by thyroid or adrenal weight, I¹³¹ uptake, or plasma free corticosteroids. In 18 graft-bearing animals, testicular weights ranged from 831 to 2,118 mg, compared to mean testis weight of 165 mg for hypophysectomized, nonimplanted animals. Histological sections of testes from these graft-bearing animals revealed active spermatogenesis. In each implanted animal with testicular maintenance, the pituitary graft was situated in the floor of the hypothalamus, encroaching upon or interrupting fibers of the supraopticohypophyseal tract. Adenohypophyseal cells which appeared to be nearest or more intimately related to these fibers were large (12–20µ), vacuolated, and contained abundant fuchsinophilic granules typical of castration cells. Other chromophil types were not present. In all nonfunctional grafts (situated in preoptic area, septum, anterior hypothalamus, and mammillary region) adenohypophyseal cells were uniformly small and chromophobic.