Aims To clarify the mechanism for cellular uptake of fluvastatin (FV) into
rat primary cultured hepatocytes and human aortic endothelial cells (HAEC).
Methods Rat primary cultured hepatocytes and Endocell-AO as normal human ao
rtic endothelial cells were used. Effects of incubation time, concentration
- and temperature-dependency on cellular FV uptake were investigated after
incubation with [C-14]-FV and its enantiomers, (+)-FV and (-)-FV. Rat prima
ry cultured hepatocytes were washed with either Na+-containing buffer or Na
+-free buffer and incubated with metabolic inhibitors or bile acids. Intrac
ellular radioactivity was measured by liquid scintillation counting. The de
termination of intracellular unchanged FV and its enantiomers was carried o
ut by stereospecific h.p.l.c.
Results In rat cultured hepatocytes, concentration- and temperature-depende
nt saturable uptake of [C-14]-FV was observed (K-m,=37.6 mu M, V-max = 869
pmol (mg protein)(-1) min(-1)), suggesting a specific uptake mechanism. The
uptake of each enantiomer also showed a specific uptake mechanism as obser
ved for the racemate with no difference between enantiomers; (+)-FV, K-m=38
.5 mu M, V-max=611 pmol (mg protein)(-1) min(-1), (-)-FV, K-m = 41.5 mu M,
V-max = 646 pmol (mg protein)(-1) min(-1). In the presence of cholate and t
aurocholate, the uptake of FV was inhibited by 39-46%. Pravastatin inhibite
d FV uptake by 29%. In the absence of Na+, the uptake of FV was markedly in
hibited 91-96% by bile acid. The uptake of FV into HAEC at 37 degrees C and
4 degrees C increased with the concentration of FV, but no saturable uptak
e was observed.
Conclusions FV transport system may be, at least in part, Na+- and ATP-depe
ndent, and may have some features in common with the bile acid transport sy
stem and the organic anion transport system. Since saturable uptake was not
observed in HAEC, FV appears to be taken up into these cells mainly via no
nspecific simple diffusion.