Palmitate uptake by hepatocyte suspensions: effect of albumin.

The clearance ratio test has been used to determine whether hepatocytes isolated from female rat livers facilitate the dissociation rate of albumin-palmitate complexes. This test requires knowledge of the clearance rate and unbound palmitate fraction at two protein concentrations. The unbound fractions have been estimated using the heptane-water partition ratio method. These fractions were determined to deviate from the expected linear relationship because of radiolabeled impurities that were still present after purification of the [3H]palmitic acid. With the use of experimentally determined partition ratio values, the palmitate clearance ratios were statistically greater than those predicted by the diffusion-reaction model at albumin concentration combinations above 99 microM/49 microM. Experimental clearance rates also exceeded those predicted by the diffusion-reaction model, but only at albumin concentrations greater than 198 microM. These data support the proposal that hepatocytes facilitate the dissociation of albumin-palmitate complexes at high albumin concentrations.