Abstract
Purpose :
Evaluating drug concentrations in different ocular tissues is important for ocular drug research. Many disease models and early pharmacokinetic investigations are performed in rats. Due to the small size of the rat eye, the separation and consecutive analysis of drug concentrations from different ocular tissues is challenging.
Methods :
We developed and validated a method of separating different ocular tissues of pigmented Brown Norway and albino Wistar Han rats with minimal cross-tissue contamination. Concentrations of model small-molecule drugs were measured from the different tissues after oral administration. We estimated the contamination from the pigmented retinal pigment epithelium-choroid to the non-pigmented retina. We also evaluated the recovery level of drug bound to melanin pigment, an issue arising in measuring concentration from pigmented ocular tissues.
Results :
Fixing the eye in paraformaldehyde before tissue isolation produced the best results with the least cross-tissue contamination. Ethanol/water (4:1) was used as the extraction solvent for all the tissues. Drug recovery from melanin was drug-dependent and optimized for each studied model drug. The pH of the extraction solvent was adjusted to provide the best extraction level from melanin. Drug concentrations differed from one tissue to another, highlighting the importance of avoiding cross-tissue contamination.
Conclusions :
The developed reproducible method facilitates the analysis of local drug concentrations in specific tissues of the rat eye, enabling the measurement of drug distribution in ocular target tissues.
This is a 2020 ARVO Annual Meeting abstract.