AUTORADIOGRAPHIC LOCALIZATION OF OESTROGEN IN RAT TISSUES

The intracellular localization of [6,7-3H]oestradiol in rat pituitary, liver and uterus has been studied using autoradiography. In the anterior pituitary the oestrogen has been located on the nuclear membrane and nucleolus of the eosinophils. The posterior pituitary did not produce positive autoradiographs and only occasional silver grains were seen in the pars intermedia. In the liver the silver grains were uniformly distributed throughout the cytoplasm; only very occasionally were grains associated with the nucleus. No satisfactory results were obtained with the uterus. Labelled erythrocytes were seen in all the tissues studied. The results are discussed in relation to the mode of action of oestradiol.

GROWTH HORMONE SECRETION IN HYPOPHYSECTOMIZED RATS WITH MULTIPLE PITUITARY TRANSPLANTS

The secretion of growth hormone from anterior pituitary transplants under the kidney capsule of gonadectomized and hypophysectomized male rats was investigated with special regard to the importance of the mass of functioning pituitary tissue. Body growth and mammary gland development after testosterone stimulation were studied.

In rats with the pituitary gland autotransplanted to the kidney capsule body growth was markedly reduced. After administration of testosterone a few groups of alveoli only were seen in the mammary glands.

Hypophysectomized rats with four pituitary transplants (an autotransplant and three homotransplants) under the kidney capsule showed slightly better body growth than rats with an autotransplanted hypophysis. When compared with rats with intact pituitary glands body growth was markedly reduced. Mammary gland development after testosterone stimulation was as poor in rats with four pituitary transplants as in rats with an autotransplanted hypophysis.

These results suggest strongly that the normal secretion of growth hormone is regulated by the hypothalamus and that the deficiency of growth hormone in rats with the pituitary gland transplanted remote from the brain is due mainly to a loss of 'specific' stimuli from the hypothalamus and not to a 'non-specific' reduction in the amount of functioning pituitary tissue.

THE INTRACELLULAR LOCALIZATION OF OESTROGEN IN RAT TISSUES

The radioactive material in rat pituitary, liver and uterus 1 hr. after the s.c. injection of either 0·73 or 7·3 μg. [6,7-3H]oestradiol has been investigated. Oestrone and oestradiol were the only compounds detected in pituitary and uterus whereas at least six compounds were present in liver.

Cell fractionation studies have been carried out on anterior pituitary and liver from female rats which had received an injection of either 0·73 or 7·3 μg. [6,7-3H]oestradiol in vivo. Most of the tritium in the anterior pituitary was associated with the nuclear fraction whereas most of the tritium in the liver was in the soluble fraction. The uptake of [6,7-3H]oestradiol by the anterior pituitary reached a maximum ½-1 hr. after injection of the steroid and remained at this level for the next 3 hr. The intracellular distribution of this steroid at different times after injection suggests that the steroid passes into the cytoplasm and then into the nucleus.

HYPOPITUITARISM DUE TO A RATHKE POUCH CYST

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