Subcellular analysis of the accumulation of estrogen by the brain of male and female rats.
Three experiments were preformed to provide additional information on the interaction of estrogen with subcellular components of the brain of male and female rats. In experiment 1 tritiated estradiol was administered to adult gonadectomized male and female rats which were then sacrificed 15,60 or 120 min later. Hypothalamic, cortical and pituitary samples were taken and were separated into nuclear and cytosol fractions. For the hypothalamic tissue from females nuclear concentration of radioactivity increased throughout the 2 h period while for males nuclear concentration rose during the first h and then declined. There was a significant sex difference in hypothalamic nuclear concentration of estrogen, male levels being lower. For both sexes cytosol levels progressively declined. For cortical tissue, nuclear radioactivity levels were low and relatively constant for both sexes, while cytosol levels fell during the 2 h period. Pituitary tissue showed a pattern in both nuclear and cytosol fractions which resembled the hypothalamic pattern although absolute levels were higher in the nuclear fraction. In experiment 2 male and female rats were administered labeled and unlabeled estradiol concurrently and were sacrificed 60 and 120 min later. Radioactivity levels were reduced in hypothalamic and pituitarynuclei, but not in cortical nuclei in comparison with animals not administered unlabeled hormone. In experiment 3 males and females were administered tritiated estradiol and were sacrificed 2 h later. The brain of each animal was split longitudinally. One half of each hypothalamic and cortical sample was subjected to nuclear separation while the other half was digested in tissue solubilizer before radioactivity counting. The former procedure showed a substantially greater nuclear concentration of radioactivity for hypothalamic tissue from females than from males. The whole tissue analysis showed only a slight sex difference for hypothalamic tissue. Sex differences were small by either procedure for cortical tissue. It was concluded that the hypothalamus of both male and female rats contains a limited capacit nuclear binding system for estrogen, but that the system is quantitatively less effective in binding estrogen in males.
D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D002369:Castration; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000378:metabolism*; D002540:Cerebral Cortex / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism*; D004958:Estradiol / Q000008:administration & dosage / Q000378:metabolism; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D007031:Hypothalamus / Q000378:metabolism; D007700:Kinetics; D008297:Male; D010902:Pituitary Gland / Q000378:metabolism; D051381:Rats; D011956:Receptors, Cell Surface; D012737:Sex Factors; D013997:Time Factors; D014316:Tritium
D004967:Estrogens; D011956:Receptors, Cell Surface; D014316:Tritium; D004958:Estradiol