ReviewEfflux transport systems for drugs at the blood–brain barrier and blood–cerebrospinal fluid barrier (Part 1)
Section snippets
Brain efflux index (BEI) method: evaluating efflux transport
An intracerebral microinjection technique that measures the fraction of drug remaining in the brain is a simple method to evaluate efflux transport. Two studies have characterized the efflux transport of 1-naphthyl-17β-glucuronide (N17βG) and a cyclic peptide, RC160 (a somatostatin analogue), following their microinjection into the cerebral cortex of rats and mice, respectively, and measurement of the radioactivity of N17βG or RC160 remaining in the brain 8., 9.. The injection site was examined
Efflux transporters: P-glycoprotein
There are two isoforms of human P-glycoprotein (P-gp) that are referred to as MDR1 and MDR2 (also called MDR3). There are three isoforms in mouse: Mdr1a (Mdr3), Mdr1b (Mdr1) and Mdr2 6., 16., 17., 18.. Human MDR1 and mouse Mdr1a and Mdr1b are primary active transporters that have broad substrate specificity for compounds such as vinca alkaloids and anthracyclines, and as a result they confer multidrug resistance to tumor cells (Table 1) 6., 16., 17., 18.. Human MDR2 and mouse Mdr2 are flippases
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