Filtered load & Rate of solute excretion

unit 4 week 13 lesson 1

process of glucose filtration

• its easily filtered, but all of it is reabsorbed and none is excreted

process of sodium in the tubules

• eaily filtered, but tubule cells do not reabsorb all of sodium

• only a fraction of sodium is excreted

renal handling

• We must first calculate how much of each substance is filtered

• this is called the filtered load

• then we can measure how much of each substance is excreted

• we can then assess renal handling of filtered items

how is filtered load calculated 

• by measuring the concentration of the substance of interest in the blood

• we also need to know what the GFR is for a person

• from there we can determien how much of an item is filtered into someones kidney

• then we can compare that to how much of an item is excreted in the collected urine

• Filtered Load = [substance]_plasma * GFR

formula for %excreted

%excreted = total excreted/filtered load x 100

how to calculate total excreted 

[substance]_urine x urine volume 

what are the normal excretion rates for sodium, potassium, and magnesium

Excretion Rate of Sodium: Normal range 0.5 - 2.5 %

Excretion Rate of Potassium: Normal range 6 - 9%

Excretion rate of Magnesium: Normal Range: 3-5%

what does it mean if excretion rates are lower or higher than expected?

• If less than expected, we can assume this is bc of the levels of ions are lower in blood plasma than it should be

• If higher than expected, we can assume lvl of ions is higher in the blood plasma than it should be

Hyponatremia

Lower than usual blood plasma levels of sodium (Na⁺)

Hypomagnesemia

Lower than usual blood plasma levels of magnesium (Mg²⁺)

Hypokalemia

Lower than usual blood plasma levels of potassium (K⁺)

Hyperkalemia

Higher than usual blood plasma levels of potassium (K⁺)

Hypernatremia

Higher than usual blood plasma levels of sodium (Na⁺)

Hypermagnesemia

Higher than usual blood plasma levels of magnesium (Mg²⁺)