The purpose of this study was to examine whether in vivo drug distribution to the brain can be reconstructed by integrating P-glycoprotein (P-gp)/mdr1a expression levels, P-gp in vitro activity, and drug unbound fractions in mouse plasma and brain. For 11 P-gp substrates, in vitro P-gp transport activities were determined by measuring transcellular transport across monolayers of mouse P-gptransfected LLC-PK1 (L-mdr1a) and parental cells. P-gp expression amounts were determined by quantitative targeted absolute proteomics. Unbound drug fractions in plasma and brain were obtained from the literature and by measuring brain slice uptake, respectively. Brain-to-plasma concentration ratios (K p brain) and its ratios between wild-type and mdr1a/1b(-/-) mice (K p brain ratio) were obtained from the literature or determined by intravenous constant infusion. Unbound brain-to-plasma concentration ratios (K p,uu,brain) were estimated from K p brain and unbound fractions. Based on pharmacokinetic theory, K p brain ratios were reconstructed from in vitro P-gp transport activities and P-gp expression amounts in L-mdr1a cells and mouse brain capillaries. All reconstructed K p brain ratios were within a 1.6-fold range of observed values. K p brain then was reconstructed from the reconstructed K p brain ratios and unbound fractions. K p,uu,brain was reconstructed as the reciprocal of the reconstructed K p brain ratios. For quinidine, loperamide, risperidone, indinavir, dexamethasone, paclitaxel, verapamil, loratadine, and diazepam, the reconstructed K p brain and K p,uu,brain agreed with observed and estimated in vivo values within a 3-fold range, respectively. Thus, brain distributions of P-gp substrates can be reconstructed from P-gp expression levels, in vitro activity, and drug unbound fractions.
|Number of pages||10|
|Journal||Journal of Pharmacology and Experimental Therapeutics|
|Publication status||Published - 2011 Nov|
ASJC Scopus subject areas
- Molecular Medicine