Lecture 7 Flashcards
Why are animals used for physiological research?
They offer greater experimental possibilities.
Shorter timeframe of experiments
Better standardisation and control
Relatively cheap to perform experiments on animals.
What are the phases of hypertension?
Development phase where BP stimuli are active.
Established phase adaptive responses take place.
Malignant phase where these control methods break down and are unable to cope with the changes.
What are some stimuli that can occur in the kidneys?
Renin release
Reduced GFR
Sodium and water retention
Increased contribution to the TPR
Efferent renal nerve stimulation
What are the adaptive responses to the stimuli of hypertension?
Cardiac Hypertrophy
Vascular hypertrophy
Altered renal pressure - natriuresis relationship; Increase in BP causes more loss of salt by kidneys. Adaptation involves modifying this relationship to decrease sodium excretion.
Sometimes postulated as BP stimuli.
How can hypertension be surgically induced?
Using rings to restrict renal blood flow. (each kidney can get 1 silver clip and so sometimes 1 kidney gets a clip and the other doesn’t and sometimes both are clipped depending on the requirement). This causes preglomerular arteriole to stretch more and increase BP via renin. As a result BP is increased. If one kidney is clipped the other one can excrete extra fluid.
Reducing renal tissue by cutting out 1 kidney and 2/3rds of the other one. another method is to wrap one kidney in cellophane.
What are some drug induced methods of hypertension?
Long term infusion of:
Angiotensin
Renin
NOS blockade (blockage of NOS synthase)
Endothelin (most potent vasoconstricter and binds irreversibly to its receptor)
Noradrenaline
Mineralcorticoid (DOCA) and high salt.
What is the result of 1k1c and 2k2c surgeries?
Brief early rise of renin
Predominant ECF expansion
Later hypertrophy of vessels and increased TPR
What happens in the 2K1C surgery?
Predominant renin release early
Unclipped kidney makes up for lost function of clipped kidney initially
Hypertension eventually damages unclipped kidney which results in ECF expansion later on
What is the DOCA-salt method?
Uninephrectomy and DOCA injection causes salt and water retention and renin is suppressed.
How is angiotensin infusion?
Pressor doses given which direct vasoconstriction and increase TPR.
Sub-pressor doses cause a direct trophic effect.
Who is more susceptible to BP stimuli?
Young people are more susceptible than old people to blood pressure stimuli. This is possibly due to hormonal milieu of growth.
What are the manifestations of the malignant phase of hypertension?
Persistently high BP
Damage to blood vessels (especially preglomerular arterioles)
Blockage of preglomerular arterioles
High renin low GFR
Rapid rise in BP and diuresis (increase in the relationship between high BP and high natriuresis)
Weight loss, illness, and even death could result
What are some examples of genetic hypertensive models?
Spontaneously Hypertensive Rats (SHR)
Dahl sensitive rat
Mice
Dogs
Chickens
What do genetic models prove about blood pressure?
That genes can affect BP
What are some features of SHR rates that can explain the increase in BP?
High sympathetic nerve activity
High renin
Reduced GFR
Na+ retention
