Pharmacokinetics of the estrogen receptor subtype-selective ligands, PPT and DPN: quantification using UPLC-ES/MS/MS.

Estrogen receptor (ER) subtype specific agonists, diarylpropionitrile (DPN) for ERß and propylpyrazoletriol (PPT) for ERα, are pharmacological probes used frequently to define mechanisms for estrogen actions in vitro and in vivo. Quantitative analytical methodology was developed and validated for DPN and PPT, based on synthetic stable labeled analogs (DPN-d(4) and PPT-d(5)) using isotope dilution liquid chromatographic tandem electrospray mass spectrometric detection. The validated method produced high sensitivity, with detection limits of 0.04-0.07ng/ml serum. Serum pharmacokinetics were evaluated in Long-Evans rats following a single subcutaneous injection (2mg/kg bw) of both compounds. The role of Phase II metabolism was evaluated using ß-glucuronidase and arylsulfatase hydrolysis to measure total DPN and PPT in addition to the parent compounds. The pharmacokinetic properties of DPN and PPT reported could facilitate experimental designs requiring specified levels of receptor occupancy for quantitative comparisons of ER subtype specificities for natural and synthetic estrogens in vivo.