Evidencing the Modulation of P-glycoprotein at Blood-Ocular Barriers using Gamma Scintigraphy

Abstract

Purpose: To evaluate the effect of P-glycoprotein modulation at blood-ocular barriers using gamma scintigraphy. Methods: Ofloxacin, a fluoroquinolone, was selected as a substrate to study the drug efflux transporter (P-glycoprotein) modulation after labeling with Technetium (^99mTc) in rabbits. New Zealand albino rabbits were randomized into two groups of 4 each. Group I received labeled ofloxacin intravitreally (100 μ Ci) and Group II animals were given verapamil intravitreally 15 min before the labeled ofloxacin. Static imaging was done at predetermined time, and dynamic images were also taken after 30 min of intravitreal injection. Results: The radio-chemical purity of labeled ofloxacin was found to be 90–95% with the labeling efficiency of 90%. The static anterior planar images of verapamil pre-treated group showed marginal increase in the uptake of labeled ofloxacin, and dynamic images showed less systemic pool as compared to its control. Conclusion: This study further confirms the findings of our laboratory regarding the involvement of P-glycoprotein in the intraocular disposition of susceptible drugs.

Keywords:

• blood-ocular barriers
• gamma scintigraphy
• P-gp
• rabbits