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Title: ATP-binding Cassette Transporter and Steroidogenesis in the
Authors: Abrar A. Alasfoor أبرار عبدالله العصفور 
Supervisor: د. بهلينج تشينج
Keywords: adrenal gland rafts ATP
Issue Date: 2015
Publisher:  Kuwait university - college of graduate studies
Abstract: Rat adrenal gland is composed of two suborgans: cortex and medulla. The cortex is organized into three distinctive zones of tissues: glomerulosa (ZG), fasciculata (ZF) and reticularis (ZF). The cortical ZF/ZR and ZG utilize cholesterol to manufacture corticosterone and aldosterone, respectively. Cholesterol is also needed for facilitation of exocytosis of the medullary chromaffin granules to release epinephrine into the circulation. Thus, to maintain cholesterol-homeostasis, adrenal cells not only express specific receptors to take up circulatory lipoprotein-cholesterol, but also express ATP-binding cassette transporters (ABCs): A1 and G1 to enhance efflux of excessive cholesterol from the cells. The present study was designed to investigate adrenal ABCA1 and ABCG1 levels under two independent stress-conditions: a daily injection of a stress hormone ACTH, and exposure to 4% KCl-fortified drinking water, for four consecutive days. The former and the latter stress-conditions stimulated adrenal productions of corticosterone and aldosterone, respectively. Immunoblot and immunohistochemistry techniques were employed for the investigation. Aldosterone synthase (CYP11B2) and 11β-hydroxylase (CYP11B1) were used as zonal markers to verify ZG and ZF/ZR, respectively. ACTH-stimulation resulted in: (a) decrease of adrenal ABCA1 and ABCG1 protein levels by 61% and 24%, respectively; (b) altered glandular distributions of the ABCs, with a striking contrast between elevated expression of the ABCs in the inner ZF/ZR and diminished expression of the ABCs in the neighboring medulla, and (c) a polarized expression of CYP11B1 that was rich in outer edge and inner portion, but sparse in the center, of the cortex. KCl-drinking water-stress caused: (a) a two-fold increase in CYP11B2 expression indicating an expansion of ZG, (b) slight changes of the ABC expression in the ZG, but adrenal protein levels remained unchanged; (c) formation of patch-like clusters of cells with massive immunolabeling of the ABCs, in the contact area between ZG and ZF. Speculatively, the intriguing alterations in the ABC-expression might be involved in readjusting cholesterol availabilities among cortical tissues for sustained steroidogenesis. Furthermore, the data also suggest that the ABCs might play additional roles in cortical tissue reorganization and communication between cortex and medulla to cope with prolonged stress.
Appears in Programs:0540 Medical Biochemistry (M.Sc.)

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