title: Effect of the Mdr1a P-glycoprotein gene disruption on the tissue distribution of SDZ PSC 833, a multidrug resistance-reversing agent, in mice.
abstract: The involvement of mdr1a P-glycoprotein (P-gP) on the tissue distribution of the multidrug resistance-reversing agent SDZ PSC 833 was assessed by use of mdr1a (-/-) mice. The mdr1a (-/-) and wild-type mdr1a (+/+) mice received a 4-h constantrate i.v. infusion (2 micrograms/min) of [14C]SDZ PSC 833. Mice were sacrificed at 0, 0.5, 1, 2 and 4 h during infusion and at 0.5, 1, 3, 8 and 24 h after stopping the infusion. Blood and tissues were analyzed on total (14C) and parental SDZ PSC 833 concentrations. Mdr1a (-/-) mice exhibited increased SDZ PSC 833 accumulation in cerebrum, cerebellum and somewhat in testes and small intestine compared with the wild-type mice. The difference between mdr1a (-/-) and (+/+) brain (cerebrum and cerebellum) penetration depended on SDZ PSC 833 blood concentrations, because this cyclosporin analog apparently governs its own brain penetration by inhibiting the P-glycoprotein pump in mdr1a (+/+) mice. Thus the mdr1a (-/-)/(+/+) ratio of brain concentrations tended to decrease and increase at high and low blood concentrations, respectively. These findings clearly demonstrate the interaction of SDZ PSC 833 with the P-glycoprotein present at the blood-brain barrier. The SDZ PSC 833 distribution in other mdr1a P-glycoprotein-expressed tissues, as well as its metabolism and elimination, was not affected by the mdr1a gene disruption. This suggests that factors other than mdr1a P-gP are involved in the disposition of this multidrug resistance-reversing agent.
authors.affiliation: CFSS, Novartis Pharma A.G., Basel, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Desrayaud
authors.forename: E C
authors.initials: EC
authors.lastname: De Lange
authors.forename: M
authors.initials: M
authors.lastname: Lemaire
authors.forename: A
authors.initials: A
authors.lastname: Bruelisauer
authors.forename: A G
authors.initials: AG
authors.lastname: De Boer
authors.forename: D D
authors.initials: DD
authors.lastname: Breimer
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000502:physiology*; D000818:Animals; D003524:Cyclosporins / Q000493:pharmacokinetics*; D018432:Drug Resistance, Multiple; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D014018:Tissue Distribution
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D003524:Cyclosporins; C070272:valspodar