7-Mammalian%20adrenal%20glands[1]

7-Mammalian%20adrenal%20glands[1] - The Mammalian Adrenal...

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1 The Mammalian Adrenal Glands Fig 8-1
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2 Adrenal cortex • Adrenal cortex: adrenocortical cells have a mesodermal origin, namely the coelomic epithelium in the pronephric region of the embryo synthesis of corticosteroids • Adrenal medulla: Adrenal medulla: chromaffin cells have a neuroectodermal origin, namely neural crest cells synthesis of catecholamines I. The mammalian adrenal cortex
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3 Zonation of the adrenal cortex • Zona glomerulosa Zona glomerulosa: smaller and more rounded cells produces mainly aldosterone (mineralocorticoid) • Zona fasciculata: bigger cells, arranged in columns produces mainly cortisol & corticosterone (glucocorticoids (glucocorticoids) • Zona reticularis: contains many connective tissue elements primary source of adrenal androgens
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4 Additional zonation
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5 Fetal zone Typical for primates • Typical for primates • Situated between cortex and medulla • Produces relatively large amounts of dehydroepiandrosterone (DHEA) as well as some DHEA sulfate It t ti t i • Important to maintain pregnancy: placenta cannot synthetise androgens, uses fetal adrenal androgens as precursors for estrogen synthesis II. Biosynthesis and transport of corticosteroids
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6 C 21 C 21 C 21 C 19 C 19 C 21 C 18
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7 Release of corticosteroids • Corticosteroids are not stored in the adrenal Corticosteroids are not stored in the adrenal, circulating levels reflect synthesis rate • Synthesis of glucocorticoids & androgens depends on ACTH stimulation • Synthesis of aldosterone is regulated by the renin-angiotensin system Transport of corticosteroids in the blood • Glucocorticoids (GC) Glucocorticoids (GC): more than 90% is bound to corticosteroid- binding globulin = transcortin bound fraction functions as hormone reservoir • Aldosterone: does not bind significantly to plasma proteins lower levels and cleared more rapidly
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8 Metabolism of corticosteroids • Liver is major site Liver is major site • Most corticosteroids are conjugated with sulfates or glucuronides increase in water solubility followed by excretion via urine, bile or faeces III. Secretion and actions of glucocorticoids
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9 Control of glucocorticoid secretion • Direct stimulation by the hypothalamus- Direct stimulation by the hypothalamus pituitary-adrenal axis involving CRH and ACTH • Direct negative feedback of glucocorticoids on ACTH release • AVP potentiates the action of CRH on ACTH release during chronic stress Actions of glucocorticoids • Bind to intracellular receptors Bind to intracellular receptors - mainly type II = glucocorticoid receptors (GR) - also type I = mineralocorticoid receptors (MR) • Major action on glucose related energy metabolism
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This note was uploaded on 10/11/2011 for the course BIOLOGY G0G49A taught by Professor V.darras during the Fall '11 term at Katholieke Universiteit Leuven.

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7-Mammalian%20adrenal%20glands[1] - The Mammalian Adrenal...

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