OAT1 Inhibition – Transfected Cells

This OAT1 transporter assay is used to screen for inhibition of OAT1 by a test compound in OAT1-transfected HEK293 cells at a single concentration

Required from Customer

  • Either a minimum of 300 µL of test compound at 10 mM in DMSO, or 5 mg of powder
  • Exact molecular mass of test compound and its salt form
  • Relevant solubility of the test compound
  • MSDS or handling and storage information, e.g., light sensitive, store at -20°C, etc.


  • Normalized uptake of para-aminohippurate (PAH) in the presence and absence of test compound in OAT1-transfected and vector control cells
  • Percent inhibition by the test compound
  • >50% inhibition indicates that the test compound is a significant inhibitor of OAT1


  • OAT1 probe substrate PAH at 10 μM
  • Test compound at 10 μM in modified Hanks’ buffer with less than 0.8% DMSO

Assay System

  • OAT1-transfected HEK293 cells and vector control cells cultured in 24-well plates

Assay Conditions

  • Measure uptake of PAH in OAT1-transfected and vector control cells with and without test compound
  • Single concentration of test compound
  • Two cell lines: OAT1-transfected and vector control cell lines
  • Four treatments as follows:
    • OAT1-transfected cells with PAH +/-test compound
    • Vector control cells with PAH +/- test compound
  • Perform assay in duplicate (N=2 per treatment)
  • Wells are equilibrated with blank buffer containing 1% BSA prior to initiating the assay
  • Buffer is aspirated and replaced with test compound dosing solution
  • Incubate cells for 5 min at 37°C
  • Terminate the incubation and lyse the cells
  • Analyze cell lysate using LC-MS/MS to determine PAH concentration
  • Determine protein concentration in cell lysate and normalize PAH concentration to protein content

Assay QC

  • Uptake rate of probe substrate in OAT1-transfected vs. vector control cells


  1. The results from this assay are provided to the customer in the ExpressPlus report format, which may include graphical representations of data and comparison with historical data for reference compounds.
  2. The solubility of the test compound in Hanks’ buffer containing < 0.8% DMSO must be greater than the test concentration. If the solubility of the test compound is unavailable, Absorption Systems can conduct a solubility assessment at an additional charge.
  3. Percent inhibition is calculated as 100 x [1-(IROAT1-IRVC)TC / (IROAT1 – IRVC)0], where IROAT1 is the influx rate of PAH in OAT1-transfected cells, IRVC is the influx rate in vector control cells, “TC”  means in the presence of test compound, and “0” means in the absence of test compound.


  1. The customer can request:
    • that a positive control be performed in parallel (additional fees apply)