Abstract
A technique for in situ vascular eye perfusion (VEP) in the guinea-pig has been developed for measurements of the blood-ocular transport kinetics of substrates under controlled conditions of arterial inflow. The blood-aqueous and blood-vitreous barriers remained intact to the vascular space marker [ 3H]dextran (MW 70 kDa) with the perfusion pressure maintained between 80 and 100 mmHg. Several 3H-, 14C- or 35S-labeled amino acids, and 3H- or 14C-labeled sucrose (extracellular space marker) were used to validate the VEP model for transport kinetic studies. Multiple time-point graphic analysis was used to estimate the compartmental unidirectional blood-ocular transport constants, K in, within the 20 min period of the VEP experiment. Blood-to-aqueous humor K in values for [ 3H]serine, [ 14C] N-methyl-α-aminoisobutyric acid (MeAIB) and [ 3H] or [ 14C]sucrose were 3·57 ± 0·38, 1·21 ± 0·13 and 1·13 ± 0·17 μl min −1 g −1, respectively. The respective blood-to-lens K in values for labeled serine, MeAIB and sucrose were 1·71 ± 0·19, 0·09 ± 0·03 and 0·03 ± 0·002 μl min −1 g −1. The uptake of newly secreted amino acids from the aqueous humor in the lens followed the order: [ 35S]methionine > [ 3H]serine ≥ [ 35S]cysteine ≥ [ 3H]alanine > [ 14C]cycloleucine ≥ [ 14C]MeAIB ≥ [ 3H] or [ 14C]sucrose. The data indicate lack of a rapid blood-to-lens uptake of two model amino acids defining the A and L amino acid carriers. A significant lenticular uptake of blood-borne substrates for the ASC amino acid transport system and of methionine was demonstrated. The utility of the VEP model to study carrier-mediated component in overall unidirectional transfer across the blood-ocular barriers was tested with serine. A strong self-inhibition of [ 3H]serine uptake into the aqueous humor (82%) and lens (77%) was obtained by unlabeled amino acid at 4·7 m m. It is concluded that the VEP technique provides a stable well-controlled environment in the choriocapillary circulation of the perfused eye suitable for examining the in situ ocular transport kinetics of different substrates.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
