title: N-(4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]-phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide (GF120918) as a chemical ATP-binding cassette transporter family G member 2 (Abcg2) knockout model to study nitrofurantoin transfer into milk.
abstract: Genetic knockout mice studies suggested ATP-binding cassette transporter family G member 2 (ABCG2)/Abcg2 translocates nitrofurantoin at the mammary-blood barrier, resulting in drug accumulation in milk. The purpose of this study was to establish the role of Abcg2 in nitrofurantoin accumulation in rat milk using N-(4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]-phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide (GF120918) as a "chemical knockout" equivalent. The inhibitory effect of GF120918 was verified in Madin-Darby canine kidney II cells stably expressing rat Abcg2 with Hoechst 33342 and nitrofurantoin flux in Transwells. Nitrofurantoin was infused (0.5 mg/h) in the absence and presence of GF120918 (10 mg/kg in dimethyl sulfoxide) to Sprague-Dawley lactating female rats using a balanced crossover design. Administration of GF120918 increased nitrofurantoin concentration in serum (from 443 +/- 51 to 650 +/- 120 ng/ml) and decreased concentration in milk (from 18.1 +/- 0.9 to 1.9 +/- 1.2 microg/ml), resulting in corresponding mean values for milk to serum concentration ratio (M/S) of 41.4 +/- 19.1 versus 3.04 +/- 2.27 in the absence and presence of GF120918 (p < 0.05), respectively. There was a decrease in systemic clearance with GF120918 (2.8 +/- 0.5 l/h/kg) compared with vehicle controls (4.1 +/- 0.5 l/h/kg; p < 0.05). Western blot analysis revealed good expression of Abcg2 and no P-glycoprotein (P-gp) expression in mammary gland, whereas immunohistochemistry confirmed the apical expression of Abcg2 in lactating mammary gland epithelia. Nitrofurantoin active transport into rat milk can be inhibited by GF120918 resulting in a 10-fold lower M/S. Although GF120918 inhibits both Abcg2 and P-gp, the high expression of Abcg2 and the absence of detectable P-gp expression in lactating mammary gland validate an important role for Abcg2 in nitrofurantoin accumulation in rat milk. GF120918 is particularly useful as a rat chemical knockout model to establish ABCG2's role in drug transfer into milk during breastfeeding.
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 725 Rose Street, Lexington, KY 40536, USA.
authors.forename: Lipeng
authors.initials: L
authors.lastname: Wang
authors.forename: Markos
authors.initials: M
authors.lastname: Leggas
authors.forename: Mamta
authors.initials: M
authors.lastname: Goswami
authors.forename: Philip E
authors.initials: PE
authors.lastname: Empey
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: McNamara
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D000166:Acridines / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001562:Benzimidazoles / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D002460:Cell Line; D004285:Dogs; D005260:Female; D005456:Fluorescent Dyes; D007262:Infusions, Intravenous; D007668:Kidney / Q000378:metabolism; D007774:Lactation / Q000378:metabolism*; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000378:metabolism; D008892:Milk / Q000378:metabolism*; D009582:Nitrofurantoin / Q000008:administration & dosage / Q000378:metabolism* / Q000493:pharmacokinetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000378:metabolism; D044005:Tetrahydroisoquinolines / Q000008:administration & dosage / Q000494:pharmacology*; D014162:Transfection
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; C489249:Abcg2 protein, rat; D000166:Acridines; D001562:Benzimidazoles; D005456:Fluorescent Dyes; D011994:Recombinant Proteins; D044005:Tetrahydroisoquinolines; D009582:Nitrofurantoin; C083501:Elacridar; C017807:bisbenzimide ethoxide trihydrochloride
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