non-endocrine endocrinology SDL

Question 1

outline the RAAS response to low blood pressure/reduced blood volume

Answer 1

1. renin released from kidneys in response to one of: Reduced sodium delivery to the distal convoluted tubule, Reduced perfusion pressure in the kidney, Sympathetic stimulation
2. angiotensin produced by liver is cleaved by renin to produce angiotensin 1
3. angiotensin 1 converted to angiotensin 2 by angiotensin converting enzyme (ACE) (this mainly occurs in the lungs)
4. angiotensin 2 exerts its action by binding receptors throughout body, resulting in vasoconstriction, Na resoption, increased release of noradrenaline, release of aldosterone and increased thrist sensation and stimulation of ADH from hypothalamus
5. angiotensin 2 acts on adrenal cortex to stimulate the release aldosterone
6. aldosterone causes kidneys to release potassium through urine which increases sodium in the bloodstream causing water retention (increases blood volume and pressure)

Question 2

what hormones are involved in the body’s response to excessive blood volume and what do they do

Answer 2

• atrial natriuretic peptide: promoting vasodilation, increasing sodium and water excretion and inhibiting release of renin and aldosterone
• brain natriuretic peptide: same as above
• aldosterone: secretion decreases leading to reduced sodium and water reabsorption by the kidneys
• anti diuretic hormone: modulating water retention

Question 3

if an animal had a gastrointestinal tumour that was making too much gastrin, what would be the clinical consequences and what might it present to a vet with

Answer 3

• low gastric pH
• ulcers
• vomiting
• inappetance
• lethargy
• weight loss
• diarrhea

Question 4

what is the link between obesity in labradors and POMC

Answer 4

The POMC gene codes for two proteins, beta-MSH (melanocyte-stimulating hormone) and beta-endorphin. These proteins are thought to play a role in satiety (signaling the brain to end the sensation of hunger once a dog eats a meal). In a dog with the POMC gene mutation, it is theorized that the brain does not receive these signals as effectively, and therefore the dog remains hungry even after an adequate meal.