GFR
Pgc-Pbs-pigc
Filterest Load
GFR x P (concentration of solute in plasma
Excreted Load
V (urine flow rate) x U (concentration of solute in urine)
RPC
V (urine volume per unit of time) x Ux (concentration of x)/ Px(plasma concentration of x)
RPC < GFR
you have to absorb some (net absorption)
RPC>GFR
you have to have secreted some (net secretion)