Changes to zonular tension alters the subcellular distribution of AQP5 in regions of influx and efflux of water in the rat lens.

Abstract

PurposeThe lens utilizes circulating fluxes of ions and water that enter the lens at both poles and exit at the equator to maintain its optical properties. We have mapped the subcellular distribution of the lens aquaporins (AQP0, 1, & 5) in these water influx and efflux zones and investigated how their membrane location is affected by changes in tension applied to the lens by the zonules. MethodsImmunohistochemistry using AQP antibodies was performed on axial sections obtained from rat lenses that had been removed from the eye and then fixed, or were fixed in situ to maintain zonular tension. Zonular tension was pharmacologically modulated by applying either tropicamide (increased), or pilocarpine (decreased). AQP labelling was visualized using confocal microscopy. ResultsModulation of zonular tension had no effect on AQP1 or AQP0 labelling in either the water efflux, or influx zones. In contrast, AQP5 labelling changed from membranous to cytoplasmic in response to both mechanical and pharmacologically induced reductions in zonular tension in both the efflux zone, and anterior (but not posterior) influx zone associated with the lens sutures. ConclusionsAltering zonular tension dynamically regulates the membrane trafficking of AQP5 in the efflux and anterior influx zones to potentially change the magnitude of circulating water fluxes in the lens.