The isolated perfused rat liver (IPRL) model provides
a mechanistic
understanding of the organic-anion-transporting polypeptide (OATP/Oatp)-mediated
pharmacokinetics in the preclinical evaluation, which often requires
the use of control substrates (i.e., pitavastatin) and monitoring
endogenous biomarkers (coproporphyrin I and III). This study aimed
to develop and validate an LC-MS method allowing the simultaneous
quantification of pitavastatin, coproporphyrin I (CPI), and coproporphyrin
III (CPIII) in rat liver perfusion matrices (perfusate, liver homogenate,
bile). The analysis was performed on a C18 column at 60 °C with
20 μL of sample injection. The mobile phases consisted of water
with 0.1% formic acid and acetonitrile with 0.1% formic acid with
a gradient flow of 0.5 mL/min. The assay was validated according to
the ICH M10 Bioanalytical Method Validation Guideline (2022) for selectivity,
calibration curve and range, matrix effect, carryover, accuracy, precision,
and reinjection reproducibility. The method allowing the simultaneous
quantification of pitavastatin, CPI, and CPIII was selective without
having carryover and matrix effects. The linear calibration curves
were obtained within various calibration ranges for three analytes
in different matrices. Accuracy and precision values fulfilled the
required limits. After 60 min perfusion with pitavastatin (1 μM),
the cumulative amounts of pitavastatin in the liver and bile were
5.770 ± 1.504 and 0.852 ± 0.430 nmol/g liver, respectively.
CPIII was a more dominant marker than CPI in both liver (0.028 ±
0.017 vs 0.013 ± 0.008 nmol/g liver) and bile (0.016 ± 0.011
vs 0.009 ± 0.007 nmol/g liver). The novel and validated bioanalytical
method can be applied in further IPRL preparations investigating Oatp-mediated
pharmacokinetics and DDIs.