Glucose is reabsorbed completely from PCT

Its reabsorbed along with sodium

Na+ is pumped out of Tubular cells by Na-K Atpase pump in the basal side

This decreases intracellular Na concentration

Uses Sodium glucose co transport (SGLT)

Thus glucose absorption from lumen is

secondary to active transport on the

basal side

Secondary active transport

SGLT 1& 2

Similar to the one present in the intestine

It transport glucose and sodium along

with various solutes like amino acids .

Lactate and phosphates

From the tubular cells glucose reaches

interstitium by GLUT-2

5

Membrane channels which helps in

transporting glucose into to cell

Induced by insulin

Facilitated transport

Totally 7 GLUT are found

For most subs that are actively secreted or reabsorbed there is a limit to rate at which solute can be transported

carrier system gets saturated if the tubular load is more than transport maximum

Tm refers to tubular load at which the carriers gets saturated

Normal TmG for males is 375mg/min

For females – 300mg/min

Tubular load is the amount of glucose filtered by the glomerulus

Tubular load of 375mg/min correspond to 300mg/dl of plasma concentration

filtered load of glucose (GFR x Pglu); units: mg/min

Filtered load of glucose = GFR x plasma [glucose]

Tubular load = 125ml/min*300 mg/dl

= 125ml/min*3mg/ml

= 375mg/min

Plasma concentration above which the

glucose first appears in urine

Normal 200mg/dl in arterial blood

180 mg/dl in venous blood

10

Region of glucose curve between

threshold and TmG

Represent the excretion of glucose in the

urine before TmG is reached

Not all nephrons have same Tm for

glucose

Overall Tm is 375 but it’s the average

variability in nephron size

Increased load of solute to tubules will

produce more urine because of osmotic

diuresis

Ex – diabetes mellitus

↑plasma glucose

↑filtered glucose

Tm exceeded

glucose remains in tubules

H2O retained osmotically

increased urine volume

if not replaced by drinking, blood volume decreases

Increased urine volume in diabetes mellitus

Normally a small amount of protein is

filtered by glomerulus and almost all of it

absorbed by PCT

150mg/day is excreted in urine normally

Constitutes 15mg of Ab and rest LMWP

and 25mg of which is Tamm horsfall

protein

Glomerluar proteinuria

Tubular proteinuria

Overflow proteinuria

Nephrogenic proteinuria