Lecture 6: Calculations and Glucose Flashcards
What contributes to final excretion of substances in urine?
Degree of reabsorption and secretion of filtered substances
Reabsorption
Water and solutes such as Na, Cl, HCO3, glucose, AA, urea, Ca, Mg, phosphate, lactate, citrate are all reabsorbed
Secretion
Organic acids and bases, K, some urea, typically secreted into tubular fluid from peritubular capillaries
If filtered load is greater than excretion rate
Net absorption of substance
If filtered load less than excretion rate
Net secretion of substance
Reabsorption or secretion rate =
Filtered load - excretion rate
Where does glucose reabsorption occur
Proximal convoluted tubule
How does glucose get across luminal membrane?
Na+/glucose co-transporter (aka SGLT 1)
How does glucose get reabsorbed from proximal tubule cell into blood?
GLUT1 or GLUT2
Glucose titration curve shows relationship between?
Plasma glucose concentration (x axis) and reabsorption (y axis)
As plasma glucose increases
Filtered load increases linearly
Why does filtered load increase linearly as plasma glucose increases?
It is a freely filtered substance
At what plasma glucose concentration is all filtered glucose reabsorbed up to? (So less than this concentration)
< 200 mg/dl
Above what value of glucose concentration are transporters limiting and the glucose curve starts to bend?
Above 200 mg/dl
At what glucose concentration are all transporters saturated and curve levels off?
Above 350 mg/dl