Gene targeting strategy for B-Mdr1 KO mice. The genome sequences between mouse Mdr1a gene and Mdr1b gene were depleted in B-Mdr1 KO mice. As a result, mouse MDR1 protein will be not expressed anymore.

Mdr1a mRNA expression analysis in wild-type C57BL/6 mice and B-Mdr1 KO mice by RT-PCR. Brain, lung and liver RNA were isolated from wild-type C57BL/6 mice and B-Mdr1 KO mice, then cDNA libraries were synthesized by reverse transcription, followed by PCR with two mouse Mdr1a primer pairs. Mouse Mdr1a mRNA was not detectable in Mdr-1 knock-out mice.

Mdr1b mRNA expression analysis in wild-type C57BL/6 mice and B-Mdr1 KO mice by RT-PCR. Brain, lung and liver RNA were isolated from wild-type C57BL/6 mice and B-Mdr1 KO mice, then cDNA libraries were synthesized by reverse transcription, followed by PCR with two mouse Mdr1b primer pairs. Mouse Mdr1b mRNA was not detectable in Mdr-1 knock-out mice.

Western blot analysis of MDR1 protein expression in B-Mdr1 KO mice. Various tissue lysates were collected from wild-type C57BL/6 mice and B-Mdr1 KO mice, and then analyzed by western blot with anti-MDR1A antibody. 40μg total proteins were loaded for western blotting analysis. MDR1 was only detectable in adrenal, brain, kidney and lung from wild-type mice but not in Mdr-1 knock-out mice.

Pharmacokinetic characteristic of B-Mdr1 KO mice. Digoxin pharmacokinetics in C57BL/6N mice co-administered with vehicle or Elacridar and in B-Mdr1 KO mice. Mice received Digoxin (1 mg/kg, PO) as a single dose. For C57BL/6N groups, either vehicle or Elacridar (50 mg/kg, PO) was administered twice daily (BID) with an 8-hour interval, with the first dose given 0.5 hours prior to digoxin. B-Mdr1 KO mice received digoxin alone. Plasma samples were collected pre-dose and at 0.25, 0.5, 1, 2, 4, 8, and 24 hours post digoxin administration (N=3 male mice per group). The plasma concentrations of digoxin in both the C57BL/6N with Elacridar group and B-Mdr1 KO mice group were higher than those in the C57BL/6N with Blank vehicle group.

Note: This experiment was conducted by Pharmaron using B-Mdr1 KO mice.