early proximal flow rate ( vep ) , an index of nephron filtration rate , was measured without perfusion of the loop of henle and during retrograde perfusion with solutions containing 20 , 35 , 60 to 100 mm nacl and varying amounts of either urea or mannitol to achieve total solute concentrations of 130 , 280 , or 400 mosm .
C0027713
nephron
C0023986
of