Measurement of the Liver Extracellular Space In Vivo in Dogs

Abstract

To obtain a reasonable estimate in vivo of the liver extracellular space (ECS) in intact, non-exsanguinated dogs, the distribution volumes of a variety of radioactive tracers were obtained as a function of time. ³⁶Cl, ¹⁴C- and ³H-inulin, ¹²⁵I-albumin, ⁵¹Cr-red cells, and endogenous ³⁵Cl distribution volumes were obtained in liver from 5 min to 4 h. The ³⁶Cl space was stable and reproducible at 29.0 %, a value similar to the endogenous ³⁵Cl (28.2 %) and 5 min ¹⁴C-inulin (29.9 %) spaces. The ³⁶Cl space may be used as the upper limit of liver ECS, whereas the inulin space exceeds this value after 5 min and progressively increases. Electrolyte concentrations in liver cell water are calculated using the ³⁶Cl space of 29 % as the liver ECS. The advantages of using ³⁶Cl over other methods to determine liver ECS in intact animals are discussed.