BSI 2 Lecture 50: Adrenal Gland Flashcards
What two portions make of the adrenal gland?
The adrenal cortex and adrenal medulla
What does the adrenal medulla secrete?
The catecholamines: epinephrine and norepinephrine
What does the adrenal cortex secrete?
Corticosteroids (aldosterone, cortisol, cortisone, and androgens)
What are the three layers of the adrenal cortex?
Zona glomerulosa, zona fasciculata, and zona reticularis
What does the zona glomerulosa secrete?
aldosterone because it expresses aldosterone synthase
What does the middle zona fasciculata secrete?
cortisol and related corticosterone plus androgen and even some estrogen
What does the zona reticularis secrete?
Androgens, androstenedione, and small amounts of estrogen and glucocorticoids
What are the steroid hormones derived from?
Cholesterol
How are steroid hormones formed?
1) ACTH binds to GPR
2) Activates AC to produce cAMP
3) cAMP activates PKA
4) PKA phosphorylates cholesterol esterase
5) Cholesterol esterase separates cholesterol from LDL
6) Cholesterol is transported to the mitochondria by StAR
7) Then it’s transported to the inner membrane by PBR
8) p450 enzymes modify cholesterol
9) Enzyme profile determines which steroid is produced
Aldosterone has a greater effect on sodium retention whereas cortisol is equally effective at _______.
sodium retention and suppressing inflammation
What percentage of plasma cortisol is bound to cortisol-binding globulin (Transcortin)?
90-95%
Why does aldosterone have a shorter half life?
Because only about 60% is bound to proteins
How are corticosteroids metabolized?
They are metabolized in the liver by conjugation to glucuronic acid which makes them more water soluble and about 75% is excreted by the kidneys while the other 25% is excreted in the feces via bile
What controls the release of Cortisol from the adrenal cortex?
Corticotropin releasing hormone from the hypothalamus, antidiuretic hormone from the posterior pituitary, and Andrenocorticotropic hormone from the anterior pituitary
What could potentially be a negative regulator of corticotropin releasing hormone?
Somatostatin
When are CRF, ACTH, and cortisol levels high?
Early in the day (6-8am)
What happens when there is a glucocorticoid imbalance?
there are serious effects on metabolism and the body’s ability to handle stress
Which glucocorticoid is secreted the most?
Cortisol (95%)
What are the glucocorticoids going to do in the liver?
Stimulate gluconeogenesis by increasing level of enzymes to convert AAs into glucose and increasing the release of AAs from muscle for gluconeogenesis
What effect can cortisol have on insulin?
It can cause decrease utilization of glucose in the cells; therefore, there is an increase in blood glucose which stimulates insulin release. However, insulin’s effectiveness in decreasing blood glucose is reduced
What could happen to blood sugar in regards to cortisol release?
It could increase to 50% greater than normal which is called adrenal diabetes, and insulin is not very effective in combatting this scenario
List the functions of glucocorticoids
1) Increased protein synthesis in liver
2) Increased lipolysis
3) Gluconeogenesis
4) Increase insulin resistance
5) Decrease inflammation
6) Decrease immune function
List functions of the catecholamines
1) Increased blood pressure
2) Increased heart rate
3) Increased blood sugar
4) Decreased GI blood flow
What does cortisol do to proteins outside of the liver?
Decreases them by decreasing synthesis and increasing catabolism
What does cortisol do to fat metabolism?
It will increase the oxidation of fatty acids from adipose tissue but over a longer period of time than what happens with decreased blood sugar
What factor can trigger the release of cortisol?
Almost any type of stress
What is the significance of cortisol release during stress?
It saves proteins from being broken down until there is no other option
What can high doses of cortisol do to inflammation?
Decrease inflammation by…
1) Decreasing the number of proteolytic enzymes
2) Decreasing capillary permeability
3) Decreasing prostaglandin production
4) Suppressing T-lymphocytes
5) Decreasing the release of interleukin-1
6) Decreasing the number of eosinophils and lymphocytes
What androgen is produced in the highest number by the adrenal cortex?
DHEA
