Age-related Macular Degeneration: Metabolic Insufficiency in the Ageing Retina?

Abstract

Abstract: : Purpose: To evaluate potential changes in the passage of water and macromolecules through Bruch's-choroid (BC) and the retinal pigment epithelium (RPE) with age. Methods: Isolated specimens of bovine non-tapetal BC with RPE (n=9, age<3 years) and without RPE (n=18, age<3 years) and human BC (n=29) were mounted in modified Ussing chambers. RPE viability was monitored by recording transepithelial voltage and resistance. Movement of macromolecules (Taurine transport, TT) was measured across bovine BC with RPE and across BC alone. Movement of water (Hydraulic conductivity, HC) and TT was measured across human BC as a function of age (1-91 years and 13-88 years) and compared to that across the RPE. Results: HC of BC declined exponentially with age (70 to 5 (m/sec/Pa)x10^-10). TT declined linearly (169.8 at age 10 years to 105.9 nm/hr/4mm at age 90 years). TT across the RPE was 30 nm/hr/4mm in the choroid to retina direction and 39.7 nm/hr/4mm in the retina to choroid direction. Conclusions: HC of human BC approximated to requirements of RPE in the elderly. Taurine transport through human BC declined with age but supply to the RPE was 2.5-3.3 fold in excess of the demand of young RPE-tissue. These results give an indication as to weighting functions, in terms of the relative contribution of the RPE and Bruch's membrane to the decline of transport capacity into and out of the ageing retina.

Keywords: age-related macular degeneration • retinal pigment epithelium • Bruch's membrane