Conventional External Irradiation Of The Whole Skull Of The Rat Blood-brain Barrier P-gp And Mrp1 Expression And Its Significance

Objective: To investigate the impact of expression and significance of P-gp ,MRP1 at blood-brain barrier after whole brain conventional fractionation irradiation in rats.Methods: According to different irradiation doses, 50 adult male Wistar rats were divided randomly into 5 groups:0Gy;10Gy;20Gy;30Gy;40Gy group. All rats were exposed to conventional fravtionation(2Gy/d, 5d/w) withγ-ray. All rats were killed and collected brain 16 hours after whole brain irradiation and detected expression of P-gp, MRP1 at BBB by SP immunohistochemistry.Result: P-gp was hign expression in 0Gy group. With the increase of radiation dose, expression of P-gp decreased to varying degree. The positive cells of P-gp were lowest in 30Gy group, it was enhanced in some extent in 40Gy group. The level of P-gp protein in 0Gy group was higher than other groups. The difference was significant (F=8. 18 q = 5. 446, 6. 67, 4. 4959 P<0. 05) . The expression of MRP1 was little in normal BBB. The positive cells of MRP1 were increased with the increase of radiation dose, and it was increased markedly in 40Gy. The difference between 30Gy and 40Gy group was significant (F=ll. 14 q=3. 36, p<0. 05)Conclusion: A certain dose irradiation can decrease the expression of P-gp, then increase drug permeability of blood-brain barrier. It can be considered as the optimum time of chemotherapy when the whole brain irradiation ranges from 20Gy to 30Gy.