In vivo evaluation of P-glycoprotein function at the blood-brain barrier in nonhuman primates using [11C]verapamil.
P-glycoprotein (P-gp) is a major efflux transporter contributing to the efflux of a range of xenobiotic compounds at the blood-brain barrier (BBB). In the present study, we evaluated the P-gp function at the BBB using positron emission tomography (PET) in nonhuman primates. Serial brain PET scans were obtained in three rhesus monkeys after intravenous administration of [(11)C]verapamil under control and P-gp inhibition conditions ([PSC833 ([3'-keto-Me-Bmt(1)]-[Val(2)]-cyclosporin) 20 mg/kg/2 h]). The parent [(11)C]verapamil and its metabolites in plasma were determined by HPLC with a positron detector. The initial brain uptake clearance calculated from the integration plot was used for the quantitative analysis. After intravenous administration, [(11)C]verapamil was taken up rapidly into the brain (time to reach the peak, 0.58 min). The blood level of [(11)C]verapamil decreased rapidly, and it underwent metabolism with time. The inhibition of P-gp by PSC833 increased the brain uptake of [(11)C]verapamil 4.61-fold (0.141 versus 0.651 ml/g brain/min, p < 0.05). These results suggest that PET measurement with [(11)C]verapamil can be used for the evaluation of P-gp function at the BBB in the living brain.
Lee
Young-Joo
YJ
The Graduate School of Pharmaceutical Sciences, the University of Tokyo, Bunkyo-ku, Japan.
Maeda
Jun
J
Kusuhara
Hiroyuki
H
Okauchi
Takashi
T
Inaji
Motoki
M
Nagai
Yuji
Y
Obayashi
Shigeru
S
Nakao
Ryuji
R
Suzuki
Kazutoshi
K
Sugiyama
Yuichi
Y
Suhara
Tetsuya
T
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D001812:Blood-Brain Barrier / Q000378:metabolism*; D002250:Carbon Radioisotopes; D002851:Chromatography, High Pressure Liquid; D003524:Cyclosporins / Q000494:pharmacology; D008253:Macaca mulatta; D008297:Male; D049268:Positron-Emission Tomography; D013379:Substrate Specificity; D014700:Verapamil / Q000494:pharmacology*
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002250:Carbon Radioisotopes; D003524:Cyclosporins; D014700:Verapamil; C070272:valspodar