The Toxicologist - Society of Toxicology

cently characterized transporter OAT5 is located on the apical membrane and may
effect reabsorption of OTxA. These uptake transporters are thought to contribute
to the toxicity of OTxA. Our hypothesis was that OTxA toxicity would be attenuated
by the OAT inhibitor probenecid (PROB) or the OAT5 substrate dihydroepiandrosterone
sulfate (DHEAS). LLC-PK1 cells were grown to confluence in
35 mm tissue culture plates and treated for 24 hr with varying concentrations of
OTxA or DHEAS. Viability was assessed by trypan blue exclusion. LC50s determined
for OTxA and DHEAS and the LC20 for DHEAS were used, as well as a
non-toxic concentration of PROB. Cultures were treated for 24 hr with OTxA (3
μM), DHEAS (5.5 or 55 μM), PROB (0.5 mM), OTxA + DHEAS, or OTxA +
PROB. The results were expressed as % viable control (%VC), defined as: [(# live
cells treated group)/( # live cells control group)] x 100. The %VC of cells treated
with OTxA alone was 57.9±5.4%. For DHEAS-treated cells (55 μM) the %VC
was 52.2±1.5%, for treatment with 5.5 μM DHEAS (n=2), 79.3% and that of
PROB-treated cells, 90.8±3.1%. Simultaneous treatment with OTxA + DHEAS
(55 μM) resulted in significantly decreased viability (31.2±0.3%), whereas the viability
of cells treated with PROB + OTxA (81.3±1.6%) was significantly higher
than OTxA alone (p