Lipophilicity and transporter influence on blood-retinal barrier permeability: a comparison with blood-brain barrier permeability

Pharm Res. 2010 Dec;27(12):2715-24. doi: 10.1007/s11095-010-0272-x. Epub 2010 Sep 22.


Purpose: To determine the lipophilicity trend line from the relationship between the blood-retinal barrier (BRB) permeability and the lipophilicity of permeants and compare it with that of the blood-brain barrier (BBB).

Methods: The retinal (RUI) and brain uptake index (BUI) of 26 radiolabeled compounds across the rat BRB and BBB, respectively, were measured using the carotid artery injection method.

Results: RUI was determined using 13 compounds expected to be transported from blood to the retina by passive diffusion and with a log n-octanol/Ringer distribution coefficient (DC) ranging from -2.56 to 2.48. The RUI values were correlated with the log of the DC [RUI = 46.2 × exp (0.515 × log DC), r(2) = 0.807]. A similar trend was obtained between BUI and lipophilicity. The RUI value for substrates of the influx transporters and P-glycoprotein (P-gp) was greater and smaller than the lipophilicity trend line, respectively. In contrast, [(3)H]verapamil, which is a substrate of P-gp, has a greater RUI value than the lipophilicity trend line, but not for BUI, suggesting that the BRB has an influx transport system for verapamil.

Conclusions: The lipophilicity trend line constructed from the RUI and DC values is considered to reflect the transport properties of drugs undergoing passive diffusion across the BRB.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blood-Brain Barrier*
  • Blood-Retinal Barrier*
  • Lipids / chemistry*
  • Male
  • Permeability
  • Pharmacokinetics
  • Rats
  • Rats, Wistar


  • Lipids