CHARACTERISTICS OF HYPOTHALAMIC AND HYPOPHYSEAL CYTOPLASMIC ESTRADIOL BINDING SUBSTANCES - EFFECTS OF NEONATAL CASTRATION AND TESTOSTERONE ADMINISTRATION

  • 1 January 1975
    • journal article
    • research article
    • Vol. 25  (4) , 279-287
Abstract
Some physicochemical characteristics and binding capacities of the cytoplasmic estradiol-receptor complexes of the rat hypophysis and hypothalamus were determined in intact males and females, neonatal castrated males and neontal and adult testosterone injected females. By gel filtration and density gradient centrifugation the hormone receptor complexes obtained in vitro, shared the same properties in both tissues. The hydrodynamic radius was estimated to be 60 .ANG., the sedimentation coefficient 8.5 S, the frictional coefficient (f/fo) was 1.42, corresponding to axial ratio (prolate) of 7.85. The MW was 263,000. The data suggest a highly asymmetric molecule similar to the uterine soluble estradiol-receptor complex. No differences were observed in the hypothalamic binding capacities of diestrous females and adult males. The results expressed as femtomole of hormone bound/milligram cytoplasmic protein were 2.40 .+-. 0.32 and 2.54 .+-. 0.26, respectively. For estrus females it was 3.72 .+-. 0.44. Neonatal castration or testosterone administration increased significantly the binding activity in adulthood. Adult females treated with testosterone showed the lowest level of the hypothalamic estradiol receptors (1.41 .+-. 0.56). No differences were observed in the in vitro titration of the pituitary cytoplasmic estrogen binding sites.