Effect of Subcutaneous Transplants of Pituitary Gland and Hypothalamus on the Estrous Cycle of the Mouse

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Abstract
Seventy-three female Fl hybrid mice (BC×C3H), 9–13 weeks of age, were treated in the following manner: (a) 26 received subcutaneous transplants of 2 whole pituitary glands from male or female donors of the same genetic constitution; (b) 11 received transplants of 2 pituitary glands and 2 pieces of cerebral cortical tissue in close proximity; (c) 24 received 2 pituitary glands and 2 pieces of hypothalamic tissue in close proximity; (d) 12 received 2 pituitary glands subcutaneously in one flank and 2 pieces of hypothalamic tissue in the opposite flank. Vaginal smears were taken daily or 6 days a week for 60 days. Vaginal cycles characterized by incomplete estrus and periods of prolonged diestrus developed soon in 21 of the 26 mice in group (a) and in 9 of the 11 mice in group (b). Such pseudopregnancy-like cycles have been shown previously to be indicative of an increased secretion of prolactin from the ectopic pituitary glands. Seventeen of the 24 mice of group (c) continued to have relatively normal cycles after transplantation. The results obtained from transplants of pituitary and hypothalamus in opposite flanks were equivocal. The mammary glands of most of the mice in groups (a) and (b) were large and lactating, especially those on the same side as the transplant. Maximal ductal and lobulo-alveolar development was evident. The pituitary gland transplants in these mice were large, and well vascularized and were composed of chromophobes and acidophils. The mammary glands of the mice in group (c) were comparable to those of untreated mice of the same sex and age. The pituitary gland transplants in these mice were small and fragmented into pieces scattered about the subcutaneous connective tissue. No neurones were identified in any of the combined transplants. It is concluded that the presence of hypothalamic tissue in close proximity to pituitary transplants causes fragmentation and resorption of much of the hypophysial transplant. This precludes the production and secretion of excessive amounts of prolactin from the graft and explains the normal estrous cycles and the lack of mammary gland development and lactation. This phenomenon does not occur when cerebral cortex is substituted for hypothalamus and is not dependent on the presence of viable neurones in the transplant site. Hypothalamic tissue had no measurable effect on already established prolactin-secreting hypophysial transplants.