Upload
dalila
View
61
Download
4
Tags:
Embed Size (px)
DESCRIPTION
Hormones of the Adrenal Cortex. Objectives Name the hormones synthesized in and secreted from adrenal cortex List the steps of synthesis of adrenal cortical hormones writing the precursors and the main enzymes involved - PowerPoint PPT Presentation
Citation preview
Hormones of the Adrenal CortexObjectives
Name the hormones synthesized in and secreted from adrenal cortexList the steps of synthesis of adrenal cortical hormones writing the precursors and the main enzymes involvedDescribe the mechanisms of storage, transport ,
degradation and excretion of each of the adrenal cortical hormones.
Explain the metabolic functions of adrenocorticosteroids
ReferencesHarper’s Biochemistry 25th and 26th eds.
04األحد، القعدة، 1429ذو1
04األحد، القعدة، 1429ذو2
Adrenal Glands
The outer part is called the adrenal cortex, which produces many different hormones called corticosteroids. This includes cortisol. These hormones regulate the salt and water balance in the body, prepare the body for stress, regulate metabolism, interact with the immune system, and induce sexual function.
The inner part, which is called the adrenal medulla, producescatecholamines, such as epinephrine. Epinephrine also known as adrenaline, increase the blood pressure and heart rate during times of stress.
04األحد، القعدة، 1429ذو3
4
Adrenal Glands
BACK 04األحد، القعدة، 1429ذو
Hormones of adrenal cortex
Three general classes of steroid hormones based on predominant functions
Mineralocorticoids: 21 carbon containing steroids , synthesized by zona glomerulosa, regulate water and electrolyte balance. Aldosterone is the most prominent mineralocorticoid.
Glucocorticoids: Also 21 carbon steroids, produced mostly in zona fasciculata and affect glucose (hence the name), amino acid and fat metabolism. Cortisol (also known as hydrocortisone) is most important GC in humans.
Androgens: The zona reticularis and fasciculata produce significant amounts of androgen precursor DHEA (dehydroepiandrosterone) and androstenedione (both 19 carbon).
04األحد، القعدة، 1429ذو5
Synthesis of Adrenocortical Hormones• Made from cholesterol taken from LDLs in the blood and stored in
adrenocortical cells
• Adrenocortical cells stimulated by ACTH or cAMP.
04األحد، القعدة، 1429ذو6
Cholesterol
Synthesis of Adrenocortical Hormones
04األحد، القعدة، 1429ذو7
Synthesis of Adrenocortical Hormones
04األحد، القعدة، 1429ذو8
Synthesis of Adrenocortical Hormones
04األحد، القعدة، 1429ذو9
Storage and secretion • Little (if any) storage of steroid hormones , directly go into
circulation as and when they are produced• Cortisol release follows the diurnal rhythm of ACTH release.
Highest levels in the morning shortly after awakening and lowest in the evening and early morning.
Plasma Transport• Cortisol circulates in plasma bound to proteins or as free. • Transcortin or corticosteroid binding globulin (CBG) binds cortisol.• Most of the steroid hormones bind to CBG.• Cortisol binds CBG and has a half life of 1.5 - 2 hrs. 8-10%
Cortisol is free. • Progesterone and deoxycorticosterone also bind CBG strongly.• Corticosterone binds CBG with less affinity.• Aldosterone does not have a specific protein but binds weekly
with albumin
04األحد، القعدة، 1429ذو10
Degradation and Excretion
• Glucocorticoids: Cortisol, Cortisone and 11-deoxycortosol are reduced by NADPH dependant enzymes and conjugated with either glucoronate or sulfate which render them water soluble. About 70% of the conjugated steroids are excreted in the urine , 20% in feces and rest exit through the skin.
• Mineralocorticoids: Aldosterone is very rapidly cleared from the plasma by liver because it lacks a specific protein carrier. It is converted to tetrahydroaldosterone 3-glucoronide which is excreted in urine.
• Androgens: are excreted as 17-keto compounds including DHEA (sulfate) as well as androstenedione and its metabolites. Small amounts of testosterone secreted by adrenals are also converted to 17-keto compounds like androsterone and etiocholanolone which are excreted in urine.
04األحد، القعدة، 1429ذو11
Metabolic functions of adrenal corticosteroidsGlucocorticoid hormones: the most important are Cortisol,
cortisone and Corticosterone
•Effects on Carbohydrate metabolism: •↑es Gluconeogenesis and glucose output•↑es amino acid utilization•↑es glycogen storage•↓es glucose uptake by tissues other than liver
•Effects on Lipid metabolism:•↑es lipolysis•↑es circulating free fatty acids (FFA)•↓ es utilization of FFA for TG synthesis.
04األحد، القعدة، 1429ذو12
Metabolic functions of adrenocorticosteroids• Effects on Protein metabolism:
• ↑es degradation of proteins in extra hepatic tissues• ↑es protein synthesis in liver
• Effects on Nucleic acid metabolism: • promotes transcription of specific genes in liver.
• Effects on water and electrolyte metabolism:• Mediated through ADH ,Deficiency causes ↑ ADH which decreases
glomerular filtration and leads to water retention.
• Other biochemical functions:• Suppress immune response in high doses (esp. cortisol)• Modulate response of catecholamines• Increase the production of gastric HCl and pepsinogen• Inhibit the bone formation- increases the risk of osteoporosis.
04األحد، القعدة، 1429ذو13
Hormones of the Adrenal Cortex
04األحد، القعدة، 1429ذو14
Androgens: DHEA and androstenedione are precursors of testosterone which is the most potent androgen. General Biochemical functions of androgens are: • Growth, development and maintenance of male
reproductive organs • Effect on protein metabolism: promote protein
synthesis , positive nitrogen balance and increase muscle mass.
• Effect on carbohydrate and fat metabolism: increase glycolysis, lipolysis and TCA cycle
• Effect on mineral metabolism: Promote mineral deposition and bone growth.
Metabolic functions of adrenocorticosteroids
04األحد، القعدة، 1429ذو15
Metabolic functions of adrenocorticosteroids
Mineralocorticoid hormones: the most active and potent mineralocorticoid is Aldosterone.
• ↑es reabsorption of sodium by the distal convoluted tubules of kidney. Water follows sodium , thus leads to water retention
• ↑es Excretion of K+, H+ and NH+4 ions in urine.
• Acts on all epithelial cells that exchange Na and water( kidney , GI tract , salivary glands etc)
• Promotes synthesis of transport proteins (pumps) which facilitate Na and water movement across cell membranes.
04األحد، القعدة، 1429ذو16
17
Hormones of the Adrenal Cortex
04األحد، القعدة، 1429ذو
04األحد، القعدة، 1429ذو 18