Effects of gender and pregnancy on hepatocellular uptake of palmitic acid: facilitation by albumin.

The human serum albumin (HSA)-dependent unbound clearance (Clu) of [3H]palmitic acid (PA) by hepatocyte suspensions isolated from immature and mature male and female and pregnant female rats was studied. The Clu values obtained experimentally were compared with the predictions of a noncompartmental diffusion-reaction (Bass-Pond) theory for the cellular uptake of protein-bound ligands. In all groups, as the concentration of HSA (Ca) was increased, there was a striking increase in Clu. These enhancement factors were predicted by the theory. Adult females had higher Clu values at high Ca values than males or immature females. Furthermore, at high Ca values, Clu in pregnant animals was twice as high as in the nonpregnant animals and four times as high as in the aged-matched males. The absolute values of Clu obtained experimentally in both pregnant and nonpregnant females exceeded the maximal predictions of the theory, using reasonable values of all of the parameters. Thus, according to current data on the physicochemical characteristics of the uptake system, the study demonstrates that some specialized process exists to facilitate hepatocellular uptake of fatty acid from albumin, and that it is potentiated by the female sex hormones.