Expression and functional activity of P-glycoprotein in cultured cerebral capillary endothelial cells.
Analysis of a panel of endothelial cells passaged between 5 and 25 times and derived from various organs and species demonstrated that murine and porcine cerebral capillary endothelial cells actively excluded the fluorescent dye rhodamine 123, a substrate of P-glycoprotein. In addition, rhodamine 123 accumulation could be enhanced by the multidrug resistance chemosensitizer verapamil, known to reduce P-glycoprotein-mediated drug efflux. Cloned murine and porcine cerebral capillary endothelial cells were immunoreactive with the C219 monoclonal antibody to P-glycoprotein, and a C219 epitope-specific blocking peptide could abolish staining. The antiproliferative and cytotoxic effects of vincristine, but not cis-platinum(II) diamminedichloride, were increased by the addition of either verapamil or cyclosporin A to brain endothelial cell cultures in a 72-h assay, as determined by [3H]thymidine incorporation and total protein measurement. Cyclosporin A was a more effective reversal agent than verapamil. Thus, a P-glycoprotein isoform may be constitutively expressed in brain endothelial cells in vitro and supports the available data on in situ immunohistochemical staining of P-glycoprotein at the blood-brain barrier. In addition, these findings may indicate that one function of P-glycoprotein in vivo at the blood-brain barrier is the exclusion of xenobiotics from central nervous system tissues.
Hegmann
E J
EJ
Cancer Research Division, Sunnybrook Health Science Centre, Toronto, Ontario, Canada.
Bauer
H C
HC
Kerbel
R S
RS
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001921:Brain / Q000098:blood supply / Q000378:metabolism; D002196:Capillaries / Q000378:metabolism; D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology; D004351:Drug Resistance; D004730:Endothelium, Vascular / Q000378:metabolism*; D006801:Humans; D008562:Membrane Glycoproteins / Q000032:analysis* / Q000276:immunology / Q000502:physiology; D051379:Mice; D020112:Rhodamine 123; D012235:Rhodamines / Q000378:metabolism; D013552:Swine; D014700:Verapamil / Q000494:pharmacology
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000911:Antibodies, Monoclonal; D008562:Membrane Glycoproteins; D012235:Rhodamines; D020112:Rhodamine 123; D016572:Cyclosporine; D014700:Verapamil