Quantification of Candesartan in Mouse Plasma by MALDI-TOFMS and in Tissue Sections by MALDI-Imaging Using the Stable-Isotope Dilution Technique

Abstract

To determine the contents of candesartan in mouse plasma, and blood vessel and kidney sliced sections and also better understand its pharmacokinetics, we applied matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and MALDI-imaging mass spectrometry (IMS) with the selected reaction monitoring (SRM) mode using a labeled-internal standard. The results of fundamental examinations showed that the slope of the resulting curves of candesartan in the plasma from the equation was 0.91 and the y-intercept was 0.02. Both intra- and inter-day accuracies (n=10) and the precision of candesartan in the plasma by MALDI-TOFMS with the SRM mode were in the range of 3.4 to 17.3% and 93.2%, respectively. The detection limit of candesartan in spiked plasma was 0.2 nmol/L. IMS analysis enabled us to clarify distinct spacial time-distribution images in sliced mouse blood vessel and kidney sections although it still needed to improve a protocol of quantification. Typical pharmacokinetic patterns of candesartan were obtained in the plasma and sliced kidney sections, but those in the blood vessel sections gradually increased 24 h after administration. MALDI-TOFMS and IMS with the SRM mode are powerful tools to identify the spacial distribution and traceability of candesartan in sliced blood vessel and tissue sections as well as in the plasma.

Keywords: MALDI-imaging; candesartan; pharmacokinetics; spacial localization; stable-isotope dilution technique.

Fig. 1. MALDI post-source decay mass spectrum of CAD and CAD-d₄ (CAD*) in the SRM mode. The monitor ions of CAD and CAD* were m/z 263.5 and m/z 267.5, respectively.

Fig. 2. Calibration curve of CAD contents between 5 nmol/L to 100 nmol/L. The calibration curve between 0.2 nmol/L to 2 nmol/L for the lower range is shown in the inset.

Fig. 3. Typical pharmacokinetic patterns in mouse plasma obtained after a single oral administration (30 mg/kg).

Fig. 4. Spacial time-distribution images in sliced mouse kidney (a) and blood vessel (b) sections by IMS with the SRM mode.

Each heat-map of the ion images at m/z 263.5 indicated the contents of CAD in sliced sections 0, 1, 6, and 24 h after the oral administration. Scanning images of each sliced section (upper) and heat-maps of ion images of CAD (lower) are shown. The data for sliced kidney was measured in single and those for blood vessel were in quadruplicate (mean±1 S.D.). #: pmol/mm²