Liver cytosolic fatty acid binding protein (FABP) represents the intracellu
lar equivalent to extracellular serum albumin, participating in the intrace
llular transport of long-chain fatty acids. In this study we observed the e
ffect of increasing and decreasing FABP levels on hepatocyte [H-3]palmitate
uptake in male Sprague-Dawley rats. We also were interested to determine w
hether uptake, from either the unbound or unbound and protein-bound fractio
ns, was fundamentally different at the different FABP levels. FABP levels w
ere modified by hypophysectomy and clofibrate treatment (50 mg/100 g body w
eight for 10 days). Results showed that the [H-3]palmitate clearance rates
paralleled the 54% decrease and 73% increase in FABP levels in hypophysecto
my and clofibrate-treated animals, respectively. In the presence of 2 and 2
0 mu M albumin, hepatocyte clearance rates of unbound [H-3]palmitate from h
ypophysectomized animals (0.16 +/- 0.01 and 0.64 +/- 0.01 mL.s(-1).10(-6) c
ells, respectively) were significantly lower (p < 0.01) than those of the s
ham group (0.30 +/- 0.02 and 1.00 +/- 0.06 mL.s(-1).10(-6) cells, respectiv
ely). However, the unbound [H-3]palmitate clearance rates from the clofibra
te-treated group (0.39 +/- 0.04 and 1.18 +/- 0.12 mL.s(-1).10(-6) cells) we
re significantly higher (p < 0.01) than the control group (0.29 +/- 0.02 an
d 0.81 +/- 0.05 mL.s(-1).10(-6) cells) for 2 and 20 mu M albumin, respectiv
ely. To investigate whether uptake was fundamentally different between the
hypophysectomized and clofibrate-treated groups, we expressed the clearance
rates as enhancement factors, i.e., EF = CL20 mu M/CL2 mu M. No statistica
l difference was observed between EF of the hypophsectomized (3.8 +/- 0.4)
and EF of the clofibrate-treated (3.1 +/- 0.3) groups, suggesting that the
extracted ligand originated from similar fractions.