CHLORIDE AND SODIUM-TRANSPORT ACROSS BOVINE CILIARY BODY EPITHELIUM (CBE)

Purpose. TO study the chloride and sodium ion transports across the bo vine ciliary body/epithelium (CBE) by a modified Ussing-Zerahn type ch amber. Methods. Isolated bovine CBE preparations were mounted in a mod ified Ussing-type chamber and the transepithelial electrical parameter s were monitored. The inward (stroma to aqueous) and outward (aqueous to stroma) fluxes of (36)[Cl] chloride and (22)[Na] sodium ions across the CBE were measured under short-circuit ed conditions. The effect o f 0.1 mM of furosemide and bumetanide on the chloride transport were s tudied. Results. The potential difference (PD), the resistance and the short-circuit current (SCC) across the isolated bovine ciliary body w ere found to be -0.20 +/- 0.01 mV (aqueous negative): 75 +/- I Omega c m(2) and -2.70 +/- 0.17 mu Acm(-2) (mean +/- SEM, n = 50) respectively . A statistically significant net inward chloride ion Aux of 1.12 +/- 0.41 mu Eq h(-1)cm(-2) (p < 0.01) was found (n = 15). The net chloride transport was abolished when 0.1 mM furosemide (82% inhibition) and 0 .1 mM bumetanide (100% inhibition) were applied bilateral. No signific ant net sodium ion flux was detected. Conclusions. Electrolyte and flu id transport across the bovine CBE may be via a bumetanide and furosem ide-sensitive chloride transport mechanism. The Na-K-2Cl cotransporter plays a significant role in the trans-CBE chloride transport. The net chloride flux/current was about 12 times higher than the measured SCC , suggesting that the chloride ion transport may be coupled to other i on species.