Effects of Stress, Circadian Rhythms, and Dietary Sodium on Brain Cell-Nuclear Uptake of Aldosterone and Corticosterone (Steroid Receptors)
Yongue, Brandon Getzen
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https://hdl.handle.net/2142/69666
Description
Title
Effects of Stress, Circadian Rhythms, and Dietary Sodium on Brain Cell-Nuclear Uptake of Aldosterone and Corticosterone (Steroid Receptors)
Author(s)
Yongue, Brandon Getzen
Issue Date
1985
Department of Study
Psychology
Discipline
Psychology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Neuroscience
Abstract
The binding of the adrenal steroid hormones aldosterone (ALD) and corticosterone (CORT) in brain cell-nuclei has been implicated as a necessary step in the behavioral and physiological actions of these hormones. In vivo uptake of radioactively labeled ALD and CORT in adrenalectomized (ADX) rats indicates a strong cell-nuclear localization of both of these hormones in limbic brain regions (such as hippocampus, septum and amygdala). However, assays of steroid uptake in ADX rats typically fail to account for the normal competition of assorted corticosteroids for corticoid binding sites in the brains of adrenal-intact subjects. In light of the greater binding affinity of the corticoid receptors for CORT than for ALD, and the greater plasma concentrations of CORT, it is possible that ALD is not bound by brain cell-nuclei in the normal, adrenal-intact subject. Moreover, description of the brain's in vivo regional uptake of these hormones in ADX rats, may be inaccurate due to labeling of heterogeneous binding sites by the single corticosteroid ligand under investigation.
Research using sub-cellular fractionation and radioimmunossay (RIA), has confirmed both the presence of endogenously secreted CORT in cell-nuclei and its limbic localization in the brains of adrenal-intact rats. To date, there are no published examinations of the brain uptake and localization of endogenously secreted ALD.
In this study, environmental and dietary factors were manipulated to induce variation in serum ALD and CORT. A series of experiments employing sub-cellular fractionation and RIA were performed, which reveal that: (1) endogenously secreted ALD and CORT, are concentrated by cell-nuclei of the brain in adrenal-intact rats, (2) the majority of the corticosteroids measured in ethanol extracts of brain cell-nuclei are associated with receptor molecules, and (3) the regional distribution of endogenously secreted ALD differs markedly from the predominantly limbic pattern predicted from in vivo uptake of labeled ALD in ADX rats. Instead, brain cell-nuclear ALD is heavily concentrated in the hypothalamus, which supports the hypothesized relationship between the interaction of ALD and angiotensin in the brain and the behavioral regulation of fluid/electrolyte balance.
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