The Accumulation, Retention and Interaction of Oestradiol and Oestrone in Central Neural and Peripheral Tissues of Gonadectomized Female Rats

Abstract

Adult female rats which had been ovariectomized and hysterectomized were given tritiated oestradiol or tritiated oestrone and killed 1, 2 or 4 h later. Several brain samples were taken including anterior hypothalamus, posterior hypothalamus, 'cerebral peduncle' and cerebral cortex. Pituitary and blood plasma samples were also taken. [3H]Oestradiol and [3H]oestrone showed different patterns of retention in basal brain structures. After[3H]oestradiol administration the anterior hypothalamus retained more radioactivity than the posterior hypothalamus, which in turn retained more radioactivity than the cerebral peduncle. With [3H]oestrone, samples from the cerebral peduncle and posterior hypothalamus retained more radioactivity than samples from the anterior hypothalamus. The cerebral peduncle and posterior hypothalamus did not differ from one another in this respect. After administration of either hormone, all basal brain structures retained more radioactivity than cerebral cortex and plasma. The pituitary retained six times more radioactivity after administration of [3H]oestradiol than after [3H]oestrone.For ovariectomized females killed 2 h after the injection of [3H]oestradiol, pretreatment with oestradiol for 30 min reduced the radioactivity retained in the pituitary and anterior hypothalamus, while pretreatment with oestradiol for 24 h produced no changes in uptake except in the uterus where radioactivity levels were nearly doubled. The increased uterine uptake was independent of increases in uterine weight. Oestrone pretreatment failed to produce consistent effects except at high doses where it reduced [3H]-oestradiol uptake in the pituitary and hypothalamus. Pretreatment with either oestrone or oestradiol had no effect on uptake by neural tissues after [3H]oestrone injection.It is concluded that there are at least four kinds of oestrogen uptake mechanisms in the female rat. The uterus contains a limited capacity

Increase in ³H-Estradiol Binding in Brain and Pituitary with Time after Gonadectomy in Adult Male and Female Rats

“…The lack of deterioration of the E2 binding mechanism during the pro longed absence of gonads is consistent with previous reports that E2-pretreatment of ovariectomized females did not result in an increase in 3H-E2 binding in the PIT or brain areas [Eisenfeld and Axelrod, 1966;Luttge and Whalen, 1972]. In addition, the lack of disappearance of E2 binding sites from the PIT and several brain areas of long-term gonadectomized ani mals is similar to E2 binding in the uterus with time after gonadectomy ( fig.…”

Sex Differences in [³H]-Estradiol Binding in Brain and Pituitary after Acute Dopaminergic Treatment

“…For convenience, radioactivity in each sample was converted to femtomoles (fmol) 3H-E2 per milligram of fresh tissue or microli ter of plasma. However, work in this [74] and other laboratories [42] has shown that toluene-extractable radioactivity from plasma con tains significant levels of E2 metabolites and. likewise, that toluene extracts of brain and pituitary contain low but detectable levels of metabolites.…”

LH Discharge Induced by Medial Preoptic Implantation of Estrone or Dopamine in the Ovariectomized Estradiol Primed Rat

“…Furthermore, in the preopticanterior hypothalamic areas, the radioactivity chromatographed as estrone was only 9-10%, in contrast with over 20% in the median eminence-posterior hypothalamic areas. The preoptic anterior hypothalamic area retained a considerable amount of estrone, which was less than cerebral peduncle or the posterior hypothalamus did (Luttge and Whalen, 1972). These facts seem to indicate a possibility that estradiol taken up in the brain tissue becomes effective after it is converted into estrone and the medial preoptic area has the estrone receptor, which could not be saturated by estradiol.…”