Restoration of ability to reject xenografts and clear carbon after hypophysectomy of adult rats.

Earlier work suggested that a new pituitary function might account for the decline of minimal O2 consumption with age by decreasing peripheral tissue responsiveness to thyroxine and triiodothyronine. It was of interest to see if removal of the pituitary from adult rats could restore juvenile competence in other systems of the body by reversing the postulated age-associated end-organ hypothyroidism. Four and 64 week old intact rats reject xenografts in 6 and 13.8 days, respectively. After hypophysectomy and thyroxine replacement, 64 week old rats reject xenografts in 6.5 days. Four and 64 week old intact rats have a Vmax of colloidal carbon clearance of 18.9 and 2.5 mg/kg fat free body weight, respectively. After hypophysectomy and thyroxine replacement 60 week old rats have a Vmax of 15.5 mg. Corticosterone was the only other hormone given to the hypophysectomized rats and at the various doses tested it did not appear to affect the rates of the two functions studied.