Download Physiology Objectives 14

Physiology Objectives 25
1.
Renal clearance: the quantity of blood plasma from which a substance has been
removed
2.
Calculate clearance by kidney of substances excreted in urine:
Clearance of x = (urine flow)([x] in urine)/([x] in plasma)
3.
Relationship of inulin clearance to GFR: since inulin is neither secreted or
reabsorbed by the tubules, inulin clearance is equal to GFR
4.
Calculate GFR: GFR = (urine flow)([inulin] in urine)/([inulin] in plasma)
5.
Renal tubular transport: removal or addition of a substance to filtrate acriss the
epithelium into the tubule lumen
Component steps in transepithelial transport: passive and active transport
6.
Two major limitations of net renal tubular transport: tubular maximum (a
maximum rate of transport that the tubules can not exceed) and gradient limitation
(gradient limitation of transport)
7.
Renal tubular reabsorption: the amount of a substance reabsorbed by the
kidneys
8.
Calculate renal tubular reabsorption:
Reabsorption rate = filtration rate – excretion rate
Reabsorption rate = (GFR)([x] in plasma) – (urine flow)([x] in urine)
9.
Luminal transport of glucose: Glucose is cotransported in with Na+. In the
early proximal tubule, this occurs via SGLT2 with low affinity and high transport
rate. In the late proximal tubule, this occurs via SGLT1 with high affinity and
low transport rate.
Basolateral transport of glucose: Glucose is passively transported via carriers.
In the early proximal tubule, this occurs via GLUT2. In the late proximal tubule,
this occurs via GLUT1
 Note: amino acids have similar schema with different transporters
10.
Clearance of a reabsorbed substance vs. filtered only: a reabsorbed substance
will have lower clearance because some of it will not appear in the urine. Since
clearance is directly proportional to the concentration of a substance excreted in
the urine, lower urine concentration leads to lower clearance
Changes in clearance of a reabsorbed substance with changes in [plasma]:
Increases in plasma concentration will increase the clearance. Though the plasma
and urine concentrations should increase at the same proportion, as the
concentration of a substance increases in the filtrate, reabsorption transporters
may become overwhelmed (via maximal rate of transport or gradient limitation)
and will not reabsorb the substance. Thus, there will be a higher concentration of
substance excreted in the urine and a higher clearance. Conversely, if there is a
decease in plasma concentration, all of the substance may be reabsorbed leading
to zero clearance of that substance.