Brain tissue distribution of MRP family members Protein and/or gene expression of MRP/Mrp isoforms in various brain compartments was compiled from reverse transcription-polymerase chain reaction, immunohistochemical, and immunoblotting studies (see text for details and references); (-) indicates negative or negligible expression reported.
| Isoform | Peripheral Sites of Expression | CNS Expression | ||||
|---|---|---|---|---|---|---|
| WB | BBB | CP | MG | AST | ||
| MRP1 | Ubiquitous (high expression in lungs, kidney, testes) | D, H, M, P, R | B, H, M, P, R | H, M, R | R | H, M, R |
| MRP2 | Liver, kidney, gut | P, R | F, H, P, R | M, R (–) | R (–) | H, R (–) |
| MRP3 | Small and large intestine, kidney, pancreas, prostate, placenta | R | B | M, R | R | R |
| MRP4 | Prostate, kidney, lungs, pancreas, testis, ovary | H, M, R | B, H, M | H, M, R | R | H, R |
| MRP5 | Ubiquitous (high levels in skeletal muscle, heart) | H, M, R | B, H, M | M, R | R | H, R |
| MRP6 | Kidney, liver (low levels in most other tissues) | H, M (–) | B | M, R (–) | R (–) | H, R (–) |
| MRP7 | Skin, colon, testes, spleen | H, M | N.D. | N.D. | N.D. | N.D. |
| MRP8 | Breast, testes, liver, placenta | H | N.D. | N.D. | N.D. | H (–) |
| MRP9 | Testes, skeletal muscle, ovary | H, M (–) | N.D. | N.D. | N.D. | N.D. |
WB, whole brain homogenate; BBB, blood-brain barrier, CP, choroid plexus; D, dog; MG, microglia; AST, astrocytes; H, human; M, mouse; R, rat; B, bovine; P, porcine; F, fish; R, rat; N.D: not determined