Transepithelial electrical measurements on the isolated rabbit iris-ciliary body.

Transmural electrical properties of the isolated rabbit iris-ciliary body (I-CB) were measured in Ussing-Zerahn-type chambers. Control p.d. across the preparation was -1.2 +/- 0.1 mV, with the ciliary process (aqueous)-side consistently negative with respect to the ciliary body (blood)-side and the short-circuit current (SCC) was 7.9 +/- 0.6 microA cm-2. Bilateral bathing solution substitutions demonstrated absolute requirements for the presence of Na+, K+ and HCO3-for the maintenance of the p.d. Addition of 5 X 10(-5) M ouabain to the aqueous-side chamber increased the p.d. and SCC initially, with a subsequent decline to zero. Only a declining phase was observed when ouabain was added to the blood-side. Ouabain inhibited oxygen consumption by 28% in Tyrode's solution. Respiratory rate was also approximately 28% lower in Na+-free and K+-free Tyrode's solution and ouabain had no additional inhibitory effect in either of these two solutions. Thus the biphasic effect of ouabain on the electrical parameters cannot be explained by a toxic effect but rather as a selective inhibition of the Na+-, K+-pump. Our results indicate that Na+-, K+-ATPase activity and the presence of HCO3- are required for active ion transport in this preparation.