Table 8

Renal plasma flow (Hct = hematocrit)

RPF = RBF * (1-Hct)

Renal resistance

R = (p_arterial – p_venous)/RBF

Renal oxygen consumption

(O₂cons)

Hemoglobin-bound O₂cons

O₂cons _chem = RBF × Hb × 1.34 × (SO_2a- SO_2v)

Physical (soluted) O₂cons

O₂cons _phys = (RPF _a × pO_2a- RPF _v × pO_2v) × 0.024/760

Total O₂cons

O₂cons _total = O₂cons _chem + O₂cons _phys

Filtration

Glomerular filtration rate

GFR ≈ Cl_crea = U/P_crea * VU

Filtration fraction

FF = GFR/RPF

Load of substance x

L_x = GFR * P_x

Tubular reabsorption/secretion

Transport (absolute)

T_x = L_x - E_x

Fractional reabsorption (relative)

RF_x = T_x/L_x

Reabsorption fraction for water

${\text{RF}}_{{\text{H}}_2\text{O}}=\left(1-\left(\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$\frac{\text{U}}{\text{P}}\text{crea}$}\right.\right)\right)$

Reabsorption fraction for sodium

${\text{RF}}_{\text{Na}}=\left(1-\left(\raisebox{1ex}{$\frac{\text{U}}{\text{P}}\text{Na}$}\!\left/ \!\raisebox{-1ex}{$\frac{\text{U}}{\text{P}}\text{crea}$}\right.\right)\right)$

Excretion

Excretion of water = urine flow

VU

Excretion of substance x

E_x = VU * U_x

Quotient U/P for substance x

U_x/P_x

(concentration of substance x:

P_x- plasma ; U_x- urine)