A Novel Method for Determination of Drug Distribution in Rat Brain Tissue Sections by LC/MS/MS: Functional Tissue Microanalysis

Abstract

Determination of drug distribution in brain and other tissues is important in pharmaceutical research. Tissue drug levels need to be determined routinely as they are usually diagnostic for both efficacy and toxicity. Determination of tissue levels in small organ subregions is frequently performed due to important functional considerations. These measurements have traditionally been very tedious requiring extensive dissection and specimen pooling to achieve detection of analytes of interest. Direct and indirect methods utilizing mass spectrometry have been reported for detection of analytes in tissue specimens. Typically, these require very specialized MS or sampling equipment and are only partially successful due to analyte response. We have developed a novel approach for quantitation of tissue sections called Functional Tissue Microanalysis (FTM) in which small circular samples are removed from subregions of interest, extracted and analyzed by conventional LC/MS/MS utilizing electrospray ionization. This allows direct measurement of regional concentrations without dissection and homogenization of tissue specimens as many subregions can be sampled from a single mounted section. Utilization of the FTM approach for analysis of both sagittal and coronal rat brain sections is shown for quantitation of raclopride and rimonabant. Reproducibility of this approach and comparison to conventional methods is reported.

Profiling of adrenocorticotropic hormone and arginine vasopressin in human pituitary gland and tumor thin tissue sections using droplet-based liquid-microjunction surface-sampling-HPLC–ESI-MS–MS

“…The use of HPLC coupled with ESI-MS/MS for detection of targeted proteins facilitates the evaluation of complex sample matrices, enables differentiation between the particular disease related materials and enables absolute analyte quantitation. [25] However, this approach traditionally requires extensive sampling and processing [26] or homogenization of tissues [27], followed by extraction and cleanup steps. While an unattended workflow might be employed for this multi-step process using conventional laboratory preparative schemes and robots, these time-consuming steps render the use of traditional HPLC/MS unrealistic for real-time or near real-time diagnostic applications.…”

Extraction efficiency and implications for absolute quantitation of propranolol in mouse brain, liver and kidney tissue sections using droplet-based liquid microjunction surface sampling high-performance liquid chromatography/electrospray ionization tande

“…No modifications to existing tissue sections are required to employ the technique. The typical sampling spatial resolution is 1–3 mm, or roughly equivalent to the size of traditional punch samples, and thereby adequate for many relevant applications involving the examination of tissue distribution of drugs and metabolites.…”

The Tissue Distribution and Urinary Excretion Study of Gallic Acid and Protocatechuic Acid after Oral Administration of Polygonum Capitatum Extract in Rats

“…Recently, several new techniques have been adopted for the analysis of drug distribution by mass spectrometry [30,31]. With improved resolving power for discriminating mass/charge ( m/z ) ratios, the application of MS to the identification and quantification of chemical compounds has become much more extensive and comprehensive [32,33].…”