The Reabsorption Rate of Substance computes the reabsorption rate of a substance based on the Glomerular Filtration Rate, concentration of the substance in plasma and urine and the flow rate of urine.

INSTRUCTIONS: Choose units and enter the following:

• (GFR)  Glomerular Filtration Rate
• (P_x) Concentration of Substance in Plasma
• (U_x) Concentration of Substance in Urine
• (V_U) Urine Flow Rate

Reabsorption Rate of Substance (Rx): The rate is returned in grams per hour.  However, this can be automatically converted to compatible units via the pull-down menu.

The Math / Science

This equation assumes the substance is only reabsorbed and not secreted.

Inputs to this equation are:

• GFR - the Glomerular Filtration Rate (see GFR)
• `P_x` - concentration of substance x in the plasma
• `U_x` - concentration of substance x in the plasma
• `V_U` - volumetric flow of urine

Notes

If a substance is only re-absorbed and not secreted, the reabsorption rate (mass absorption rate) of the substance can be computed as the difference between the amount filtered per unit time of the substance and the excretion rate of the substance, where:

mass filtration rate = `GFR * P_x`

and

excretion rate = `U_x * V_U`