This equation computes the reabsorption rate, `R_x` of some substance, x.  \

This equation uses the GFR _1 as an equation-in-equation to computer the GFR term of the Reabsortption Rate [GFR] equation.

Inputs to this equation are:

• `K_f` - Filtration coefficient
• `P_"GC"`- Glomerular Pressure, the pressure in the glomerular capillaries that are enclosed in the Bowman's capsule
• `P_"BC"`- Bowman’s Capsule Pressure, the fluid pressure in the Bowman's capsule
• `Pi_"GC"` - Glomerular Oncotic Pressure (also known as colloid osmotic pressure), the osmotic pressure tending to pull water into the glomerular capillaries,  into the circulatory system
• `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`