AJP - Renal Physiology, Vol 237, Issue 3 210-F217, Copyright © 1979 by American Physiological Society
Transport and metabolism of octanoate by the perfused rat kidney
M. E. Trimble
These studies were done to determine the capacity of the perfused rat
kidney to metabolize and transport the medium-chain fatty acid, octanoate
(C8). Use of C8, which is water soluble, facilitated the study of
transport, since protein, normally needed to transport long-chain fatty
acids in solution, could be omitted from the perfusate. Using a filtering
kidney it was found that total metabolism and incorporation of
[1-14C]octanoate occurred at a rate of 3.9 +/- 0.3 micromol-g wet wt-1-20
min-1 when the perfusate octanoate was 2.8 mM, and reabsorptive uptake
occurred at the rate of 7.5 +/- 1.3 micromol-g wet wt-1-20 min-1 at the
same octanoate concentration. Use of a nonfiltering kidney (10% dextran
perfusate) allowed quantitation of peritubular octanoate uptake. This
peritubular uptake showed saturation above 0.7 mM perfusate octanoate with
an apparent transport maximum (Tmax) at 2.1 micromol-g wet wt-1-20 min-1.
Many previous experiments have linked renal fatty acid transport with that
of the organic anion transport system. The apparent peritubular Tmax
observed for octanoate suggests carrier-mediated transport. However, this
transport did not appear to be inhibited by other organic acids such as
probenecid (1--2 mM) and p-aminohippurate (1--2 mM).
