Fluid Movement Across the Surface of the Isolated Bovine Lens

Abstract

Abstract: : Purpose: Fluid transport across the crystalline lens surface is expected to be associated with ionic transport described in the epithelial and equatorial regions. Predictions of fluid movement by the model of Mathias et al. do not agree with measurements by Fischbarg et al. across the rabbit lens. Thus, we have used the large (18-mm equatorial diameter), freshly isolated bovine lens to detect fluid movement. Methods: Bovine lenses were isolated in a chamber in which 2 O-rings separated the lens semi-spherical surface into 3 regions: anterior pole (8-mm diameter), epithelial-equatorial (E-Eq), and posterior face. The chamber was closed except for a connection from each of the 3 compartments to its own capillary, which was used to measure volume changes. Changes in one capillary are compensated by opposite changes in the other(s) capillary(ies), so that the volume in the system is constant. Temperature was maintained at 36.5 ± 0.1 °C. Results: In about 40% of the isolated lenses, an efflux of about 3.0 ± 1.5 µl/hr (n= 15) was observed across the E-Eq area that was balanced by equivalent influxes across the anterior pole and posterior face. In the other 60%, measurements were either unreliable or no fluid movement was observed. Hyperosmolarity (+100 mM sucrose) in the anterior-pole compartment markedly reduced the efflux across the E-Eq surface. Addition of a dye to any of the compartments showed a complete isolation between the anterior pole and E-Eq region. In some cases, the dye traveled between the posterior and E-Eq compartments along the capsule and superficial fibers. Conclusions: The present results support the model of Mathias et al. Ionic currents in the bovine lens need to be characterized to determine if the fluid values are consistent with ionic transport. The position and size of the O-rings that delimit the isolated surfaces may also influence the obtained values. We expect the success rate to improve as the technique is further developed.

Keywords: anterior chamber • ion channels • ion transporters