Incorporation of 17β-Estradiol-6,7-³H Into the Anterior Pituitary Gland of Rats Bearing a Hormone-Secreting Pituitary Tumor

Summary

Female Buffalo rats were implanted subcutaneously with a prolactin- and adrenocorticotropin-secreting pituitary tumor, 7315a, and were ovariectomized-adrenalectomized or ovariectomized 3–6 weeks later. The rats were inoculated once intraperitoneally or intravenously with 0.1 μg 17β-estradiol-6,7-³H/100 g body weight 4 days or 5 weeks after endocrine ablation and killed 1 hour later. The amount of isotope bound to the nucleus of the anterior pituitary gland was not statistically different between the tumor-bearing and non-tumor-bearing controls. The hypothalamus and uterus of tumor-bearing rats bound less radioactive estradiol than control tissues, but the data were not statistically different. When estradiol was administered intravenously, plasma values were significantly lower in the tumor-bearing than in control rats. This was associated with considerable incorporation of the radioactive estradiol into the tumor. When incubated in vitro with radioactive estradiol, pituitary glands from tumor-bearing and control rats bound similar amounts of isotope. These data show that under the conditions of these experiments, pituitary glands from tumor-bearing and non-tumor-bearing rats could bind comparable amounts of radioactive estradiol, and, therefore, the inhibition of prolactin synthesis in pituitary glands from tumor-bearing animals, previously described, cannot be due to a pituitary tumor hormone-induced inhibition of estrogen binding by the pituitary gland.