title: Functional Characterization of Carrier-Mediated Transport of Pravastatin across the Blood-Retinal Barrier in Rats.
abstract: Systemically administered pravastatin effectively treats diabetic retinopathy without central nervous system side effects. The efflux transport mechanism of pravastatin from the brain has already been clarified. In this study, the influx of pravastatin across the blood-retinal and blood-brain barriers (BRB and BBB) and the efflux of pravastatin from the retina were investigated using rats. Pravastatin influx (blood-to-tissues) was assessed using the retinal and brain uptake index (RUI and BUI) methods, and microdialysis was performed to investigate the efflux (retina-to-blood) transport of pravastatin. The RUI and BUI values for [(3)H]pravastatin were lower than those expected based on its lipophilicity, suggesting that the influx transport across the BRB and BBB was less than the reverse-direction transport. The RUI and BUI values for [(3)H]pravastatin were significantly decreased by pravastatin, digoxin, and probenecid, indicating that pravastatin undergoes carrier-mediated influx transport in the blood-to-tissues direction across the BRB and BBB. After intravitreal injection, [(3)H]pravastatin and the bulk flow marker [(14)C]d-mannitol were found to be eliminated biexponentially from the vitreous humor. The elimination rate constant of [(3)H]pravastatin during the terminal phase was 1.66-fold greater than that of [(14)C]d-mannitol. Efflux transport was reduced in the retinal presence of pravastatin, digoxin, and benzylpenicillin, suggesting that pravastatin is transported via efflux transporters. In conclusion, pravastatin is transported across the BRB via uptake and efflux transporters in both the blood-to-retina and retina-to-blood directions, and the retina-to-blood transporters are dominant, based on the lower values of the RUI compared with the values expected from the lipophilicity.
authors.affiliation: Nara Research and Development Center, Santen Pharmaceutical Co., Ltd., Ikoma, Nara, Japan (S.F., C.S., K.K.); Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan (S.F., K.H.) shinobu.fujii@santen.co.jp.
authors.forename: Shinobu
authors.initials: S
authors.lastname: Fujii
authors.affiliation: Nara Research and Development Center, Santen Pharmaceutical Co., Ltd., Ikoma, Nara, Japan (S.F., C.S., K.K.); Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan (S.F., K.H.).
authors.forename: Chikako
authors.initials: C
authors.lastname: Setoguchi
authors.affiliation: Nara Research and Development Center, Santen Pharmaceutical Co., Ltd., Ikoma, Nara, Japan (S.F., C.S., K.K.); Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan (S.F., K.H.).
authors.forename: Kouichi
authors.initials: K
authors.lastname: Kawazu
authors.affiliation: Nara Research and Development Center, Santen Pharmaceutical Co., Ltd., Ikoma, Nara, Japan (S.F., C.S., K.K.); Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan (S.F., K.H.).
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Hosoya
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000172:deficiency / Q000502:physiology*; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D001812:Blood-Brain Barrier / Q000378:metabolism; D001813:Blood-Retinal Barrier / Q000378:metabolism*; D008297:Male; D017035:Pravastatin / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D055647:Rats, Transgenic; D014822:Vitreous Body / Q000378:metabolism
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; C095122:multidrug resistance protein 3; D017035:Pravastatin