Renal Blood Flow Flashcards
Describe the effect of the Sympathetic nervous system on RBF and GFR.
SNS results in vasocontriction:
— Renal arterioles causing a decrease in RBF and GFR by a1- adrenoceptors
Ex. NE, dopamine, Circulating E.
Describe the effect of Prostoglandins (PGs) on the regulation of RBF and GFR.
PGs results in the vasodilation of afferent (renal) arterioles therefore increasing RBF and GFR.
Ex. Prostaglandins E2 and I2, bradykinin, NO and Dopamine.
Note: NSAID decrease synthesis of Pgs.
Describe the renal handling of glucose.
Glucose is reabsorbed in the early PT (proximal tubule). It involves Na+ transport through the basolateral membrane and enters the PT with glucose attached to a Na- glucose attachment. Once it enters, glucose leaves the cell via the basolateral membrane via glucose transporters, GLUT 1 & 2 and moves into the blood stream.
Describe Glucose reabsorption in the early PT.
Glucose is reabsorbed back into the PT once the value is less that its tubal transport maximum, Tm= 325.
If the value is less than 325, it is all reabsorbed back into the blood stream.
If the value is higher than 325, it is not all reabsorbed and leaks into the urine causing glucosuria.
State the effects of the plasma glucose concentrations on glucose handling.
If the plasma glucose concentration is <200 mg/dl, glucose is reabsorbed back into the blood.
If the plasma glucose concentration is >200mg/dl, glucose is not reabsorbed and is excreted in the urine.
Give some example of Glucosuria.
Uncontrolled DM
Pregnancy
Na+ glucose cotransporter.
Describe the Isosmotic (water & solutes) Reabsorption routes in PT
Step 1. Na+ enters the PT via the lumen membrane and water follows to maintain isomolarity.
Step 2. Na+ leaves the PT via the Na/K/ATPase pump and enters the peritubular capillary.
Step 3. The water present in the intercellular space is act on by the starling forces that drives the water into the PC.
Describe the effect of Atrial natriuretic peptide (ANP) on RBF.
ANP:
— causes vasodilation of afferent arterioles therefore causing a increase in RBF.
— causes vasoconstriction of efferent arterioles there causing an increase in RBF.
State the mechanisms of autoregulation of RBF.
- Myogenic mechanism
- Tubuloglomerular feedback.
Explain the mechanism, Myogenic mechanism, on the autoregulation of RBF.
— Responds to an increase in renal arterial pressure.
— an increase in renal arterial pressure leads to an increase in stretch of the arterioles, contracts and increase resistance, and BF to maintain RBF, GFR.
Explain the mechanism, tubuloglomerular feedback, on the autoregulation of RBF.
— based on the increased arterial pressure that’s leads to an increase in fluid delivery to macula densa.
— The increase in load causing constriction of afferent arterioles and increases resistance to maintain RBF.
Explain how a high protein diet can increase in GFR via tubuloglomerular feedback.
A high protein diet causes:
— an increase in Na+ and Cl- reabsorption
— decrease in Na+ and Cl- delivery in the macula densa, which results in an increase in GFR.
State the equation of RPF and RBF.
RPF= UxV/ P then substitute value in RBF.
RBF = RPF- 1- Hematocrit
Describe the effect of Angiotensin II (AgII) on the regulation of RBF and GFR.
AgII —
1) Low AgII on efferent arterioles causes vasocontriction, decrease RBF and increase GFR.
2) **High AgII* on efferent and afferent arterioles causes vasoconstriction, decreasing RBF and GFR.
Describe the effect of the hormone, Endothelin, on the regulation of RBF and GFR.
— results in vasocontriction of afferent and efferent arterioles, decrease RBF and GFR.
